For More Information
SUSE Linux
Reference
www.novell.com
10.0
09/12/2005
Reference
List of Authors: Jörg Arndt, Stefan Behlert, Frank Bodammer, James Branam, Volker Buzek, Klara
Cihlarova, Stefan Dirsch, Olaf Donjak, Roman Drahtmüller, Thorsten Dubiel, Torsten Duwe, Thomas
Fehr, Stefan Fent, Werner Fink, Kurt Garloff, Joachim Gleißner, Carsten Groß, Andreas Grünbacher,
Berthold Gunreben, Franz Hassels, Andreas Jaeger, Jana Jaeger, Klaus Kämpf, Andi Kleen, Hubert
Mantel, Lars Marowsky-Bree, Chris Mason, Johannes Meixner, Lars Müller, Matthias Nagorni, Anas
Nashif, Siegfried Olschner, Edith Parzefall, Peter Pöml, Thomas Renninger, Hannes Reinecke, Thomas
Rölz, Heiko Rommel, Marcus Schäfer, Thomas Schraitle, Klaus Singvogel, Hendrik Vogelsang, Klaus
G. Wagner, Rebecca Walter, Christian Zoz
This publication is intellectual property of Novell Inc.
Its contents can be duplicated, either in part or in whole, provided that a copyright label is visibly located on each copy.
All information found in this book has been compiled with utmost attention to detail. However, this
does not guarantee complete accuracy. Neither SUSE LINUX GmbH, the authors, nor the translators
shall be held liable for possible errors or the consequences thereof.
Many of the software and hardware descriptions cited in this book are registered trademarks. All trade
names are subject to copyright restrictions and may be registered trade marks. SUSE LINUX GmbH
essentially adheres to the manufacturer's spelling. Names of products and trademarks appearing in
this book (with or without specific notation) are likewise subject to trademark and trade protection
laws and may thus fall under copyright restrictions.
Please direct suggestions and comments to [email protected]
Contents
About This Guide
xv
Part I Advanced Deployment Scenarios
19
1 Remote Installation
21
1.1
1.2
1.3
1.4
1.5
Installation Scenarios for Remote Installation . . . .
Setting Up the Server Holding the Installation Sources
Preparing the Boot of the Target System . . . . . .
Booting the Target System for Installation . . . . . .
Monitoring the Installation Process . . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2 Advanced Disk Setup
2.1
2.2
2.3
21
30
40
49
53
57
Permanent Device Names for SCSI Devices . . . . . . . . . . . . . .
LVM Configuration . . . . . . . . . . . . . . . . . . . . . . . .
Soft RAID Configuration . . . . . . . . . . . . . . . . . . . . . .
57
58
65
Part II Internet
71
3 The Web Browser Konqueror
73
3.1
3.2
3.3
3.4
3.5
3.6
Tabbed Browsing . .
Saving Web Pages and
Internet Keywords .
Bookmarks . . . . .
Java and JavaScript .
For More Information
. . . . .
Graphics .
. . . . .
. . . . .
. . . . .
. . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
74
75
75
76
76
77
4 Firefox
4.1
4.2
4.3
4.4
4.5
4.6
4.7
79
Navigating Web Sites . . . .
Finding Information . . . . .
Managing Bookmarks . . . .
Using the Download Manager .
Customizing Firefox . . . . .
Printing from Firefox . . . .
For More Information . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
5 Linphone—VoIP for the Linux Desktop
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
89
Configuring Linphone . . . . . . . . . . . . . . . . . . . . . . .
Testing Linphone . . . . . . . . . . . . . . . . . . . . . . . . .
Making a Call . . . . . . . . . . . . . . . . . . . . . . . . . . .
Answering a Call . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Address Book . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . .
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
For More Information . . . . . . . . . . . . . . . . . . . . . . .
6 Encryption with KGpg
6.1
6.2
6.3
6.4
6.5
6.6
Generating a New Key Pair
Exporting the Public Key .
Importing Keys . . . . .
The Key Server Dialog . .
Text and File Encryption . .
For More Information . .
89
94
95
96
96
97
98
99
101
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .
101
103
104
105
107
108
Part III Multimedia
109
7 Sound in Linux
111
7.1
7.2
7.3
7.4
7.5
Mixers . . . . . . . . . . . . . . . .
Multimedia Players . . . . . . . . . . .
CDs: Playback and Ripping . . . . . . . .
Hard Disk Recording with Audacity . . . .
Direct Recording and Playback of WAV Files
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
8 TV, Video, Radio, and Webcam
8.1
8.2
8.3
iv
79
81
81
84
84
87
87
Watching TV with motv . . . . . . . . . . . . . . . . . . . . . .
Video Text Support . . . . . . . . . . . . . . . . . . . . . . . .
Webcams and motv . . . . . . . . . . . . . . . . . . . . . . .
111
116
121
125
128
131
131
134
134
8.4
8.5
nxtvepg—The TV Magazine for Your PC . . . . . . . . . . . . . . .
Watching Digital Video Broadcasts with xawtv4 . . . . . . . . . . . .
9 K3b—Burning CDs or DVDs
9.1
9.2
9.3
9.4
9.5
9.6
Creating a Data CD . . . . . . .
Creating an Audio CD . . . . .
Copying a CD or DVD . . . . .
Writing ISO Images . . . . . . .
Creating a Multisession CD or DVD
For More Information . . . . .
134
136
141
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. .
. .
. .
. .
. .
. .
141
144
145
146
146
147
Part IV Office
149
1 0 The OpenOffice.org Office Suite
151
10.1
10.2
10.3
10.4
10.5
10.6
Compatibility with Other Office Applications
Word Processing with Writer . . . . . . .
Introducing Calc . . . . . . . . . . . .
Introducing Impress . . . . . . . . . .
Introducing Base . . . . . . . . . . . .
For More Information . . . . . . . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
.
.
.
.
.
.
1 1 Evolution: An E-Mail and Calendar Program
11.1
11.2
11.3
11.4
11.5
11.6
11.7
11.8
Importing E-Mail from Other Mail Programs
Evolution Overview . . . . . . . . . . .
Mail . . . . . . . . . . . . . . . . .
Contacts . . . . . . . . . . . . . . .
Calendars . . . . . . . . . . . . . . .
Syncing Data with a Handheld . . . . . .
Evolution for GroupWise Users . . . . . .
For More Information . . . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
159
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1 2 Kontact: An E-Mail and Calendar Program
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
Importing E-Mail from Other Mail Programs
Kontact Overview . . . . . . . . . . .
Mail . . . . . . . . . . . . . . . . .
Contacts . . . . . . . . . . . . . . .
Calendar . . . . . . . . . . . . . . .
Syncing Data with a Handheld . . . . . .
Kontact for GroupWise Users . . . . . .
For More Information . . . . . . . . .
.
.
.
.
.
.
.
.
152
153
156
156
157
157
159
160
161
165
167
168
168
169
171
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
171
172
174
178
180
182
182
184
v
1 3 Synchronizing a Handheld Computer with KPilot
13.1
13.2
13.3
13.4
13.5
Conduits Used by KPilot . . . . . .
Configuring the Handheld Connection
Configuring the KAddressBook Conduit
Managing To-Do Items and Events . .
Working with KPilot . . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
185
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1 4 Using Beagle
14.1
14.2
193
Indexing Data . . . . . . . . . . . . . . . . . . . . . . . . . .
Searching Data . . . . . . . . . . . . . . . . . . . . . . . . .
194
196
Part V Graphics
199
1 5 Digital Cameras and Linux
201
15.1
15.2
15.3
15.4
15.5
15.6
Connecting to the Camera
Accessing the Camera . .
Using Konqueror . . . . .
Using Digikam . . . . . .
Using f-spot . . . . . . .
For More Information . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. .
. .
. .
. .
. .
. .
1 6 Kooka—A Scanning Application
16.1
16.2
16.3
16.4
16.5
The Preview . . . . . . . .
The Final Scan . . . . . . .
The Menus . . . . . . . .
The Gallery . . . . . . . .
Optical Character Recognition
.
.
.
.
.
.
.
.
.
.
17.1
17.2
17.3
17.4
17.5
17.6
Graphics Formats . . .
Starting GIMP . . . . .
Getting Started in GIMP .
Saving Images . . . . .
Printing Images . . . .
For More Information .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
201
202
202
203
212
218
219
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1 7 Manipulating Graphics with The GIMP
vi
186
187
188
188
190
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
220
221
222
223
224
225
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
225
226
228
229
231
232
Part VI Mobility
233
1 8 Mobile Computing with Linux
235
18.1
18.2
18.3
18.4
Laptops . . . . . . . .
Mobile Hardware . . . .
Cellular Phones and PDAs .
For More Information . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. .
. .
. .
. .
1 9 PCMCIA
19.1
19.2
245
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Software . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 0 System Configuration Profile Management
20.1
20.2
20.3
20.4
20.5
20.6
20.7
Terminology . . . . . . . . . . . . . . .
Using the YaST Profile Manager . . . . . .
Configuring SCPM Using the Command Line .
Using the Profile Chooser Applet . . . . . .
Troubleshooting . . . . . . . . . . . . .
Selecting a Profile When Booting the System .
For More Information . . . . . . . . . .
Power Saving Functions . . . . . .
APM . . . . . . . . . . . . . .
ACPI . . . . . . . . . . . . . .
Rest for the Hard Disk . . . . . .
The powersave Package . . . . . .
The YaST Power Management Module
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
247
248
252
255
256
257
257
259
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2 2 Wireless Communication
22.1
22.2
22.3
245
246
247
2 1 Power Management
21.1
21.2
21.3
21.4
21.5
21.6
235
242
243
243
Wireless LAN . . . . . . . . . . . . . . . . . . . . . . . . . .
Bluetooth . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Infrared Data Transmission . . . . . . . . . . . . . . . . . . . .
260
261
262
269
270
278
283
283
293
304
Part VII Administration
307
2 3 Security in Linux
309
23.1
Masquerading and Firewalls . . . . . . . . . . . . . . . . . . . .
309
vii
23.2
23.3
23.4
SSH: Secure Network Operations . . . . . . . . . . . . . . . . . .
Encrypting Partitions and Files . . . . . . . . . . . . . . . . . . .
Security and Confidentiality . . . . . . . . . . . . . . . . . . . .
2 4 Access Control Lists in Linux
24.1
24.2
24.3
24.4
24.5
Advantages of ACLs . . .
Definitions . . . . . . .
Handling ACLs . . . . . .
ACL Support in Applications
For More Information . .
. . .
. . .
. . .
. . .
. . .
341
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. .
. .
. .
. .
. .
2 5 System Monitoring Utilities
25.1
25.2
25.3
25.4
25.5
25.6
25.7
25.8
25.9
25.10
25.11
25.12
25.13
25.14
25.15
25.16
25.17
25.18
25.19
25.20
25.21
25.22
List of Open Files: lsof . . . . . . . . .
User Accessing Files: fuser . . . . . . . .
File Properties: stat . . . . . . . . . . .
USB Devices: lsusb . . . . . . . . . . .
Information about a SCSI Device: scsiinfo .
Processes: top . . . . . . . . . . . . .
Process List: ps . . . . . . . . . . . . .
Process Tree: pstree . . . . . . . . . .
Who Is Doing What: w . . . . . . . . . .
Memory Usage: free . . . . . . . . . .
Kernel Ring Buffer: dmesg . . . . . . . .
File Systems and Their Usage: mount, df, and
The /proc File System . . . . . . . . . .
vmstat, iostat, and mpstat . . . . . .
procinfo . . . . . . . . . . . . . . .
PCI Resources: lspci . . . . . . . . . .
System Calls of a Program Run: strace . . .
Library Calls of a Program Run: ltrace . . .
Specifying the Required Library: ldd . . . .
Additional Information about ELF Binaries . .
Interprocess Communication: ipcs . . . . .
Time Measurement with time . . . . . . .
341
342
343
351
351
353
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
du
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
353
355
355
356
356
357
358
359
360
361
361
362
363
365
365
366
367
368
369
369
370
370
Part VIII System
371
2 6 32-Bit and 64-Bit Applications in a 64-Bit System Environment
373
26.1
26.2
26.3
viii
320
325
328
Runtime Support . . . . . . . . . . . . . . . . . . . . . . . .
Software Development . . . . . . . . . . . . . . . . . . . . . .
Software Compilation on Biarch Platforms . . . . . . . . . . . . . .
373
374
374
26.4
Kernel Specifications . . . . . . . . . . . . . . . . . . . . . . .
2 7 Working with the Shell
27.1
27.2
27.3
27.4
Using of Bash on the Command
Users and Access Permissions .
Important Linux Commands . .
The vi Editor . . . . . . . .
377
Line
. .
. .
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2 8 Booting and Configuring a Linux System
28.1
28.2
28.3
The Linux Boot Process . . . . . . . . . . . . . . . . . . . . . .
The init Process . . . . . . . . . . . . . . . . . . . . . . . . .
System Configuration via /etc/sysconfig . . . . . . . . . . . . . . .
Boot Management . . . . . . . . .
Selecting a Boot Loader . . . . . . .
Booting with GRUB . . . . . . . . .
Configuring the Boot Loader with YaST
Uninstalling the Linux Boot Loader . .
Creating Boot CDs . . . . . . . . .
The Graphical SUSE Screen . . . . .
Troubleshooting . . . . . . . . . .
For More Information . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Information about Special Software Packages
Virtual Consoles . . . . . . . . . . . . .
Keyboard Mapping . . . . . . . . . . . .
Language and Country-Specific Settings . . .
Workflow of the Printing System . . . . . .
Methods and Protocols for Connecting Printers
Installing the Software . . . . . . . . . .
Configuring the Printer . . . . . . . . . .
Configuration for Applications . . . . . . .
Special Features in SUSE Linux . . . . . . .
Troubleshooting . . . . . . . . . . . . .
428
428
429
439
444
444
445
446
447
449
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3 1 Printer Operation
31.1
31.2
31.3
31.4
31.5
31.6
31.7
411
414
423
427
3 0 Special Features of SUSE Linux
30.1
30.2
30.3
30.4
377
388
393
405
411
2 9 The Boot Loader
29.1
29.2
29.3
29.4
29.5
29.6
29.7
29.8
29.9
376
449
456
456
457
461
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
462
463
464
464
470
471
476
ix
3 2 The Hotplug System
32.1
32.2
32.3
32.4
32.5
32.6
485
Devices and Interfaces . . .
Hotplug Events . . . . . .
Hotplug Device Configuration
Automatic Module Loading .
The Boot Script Coldplug . .
Error Analysis . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3 3 Dynamic Device Nodes with udev
33.1
33.2
33.3
33.4
33.5
491
Creating Rules . . . . . . . . . . . . .
Placeholder Substitution . . . . . . . .
Pattern Matching in Keys . . . . . . . .
Key Selection . . . . . . . . . . . . .
Persistent Names for Mass Storage Devices
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3 4 File Systems in Linux
34.1
34.2
34.3
34.4
34.5
Terminology . . . . . . .
Major File Systems in Linux
Some Other Supported File
Large File Support in Linux
For More Information . .
. . . .
. . . .
Systems
. . . .
. . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
X11 Setup with SaX2 . . . . .
Optimizing the X Configuration
Installing and Configuring Fonts
OpenGL—3D Configuration . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Structure of a PAM Configuration File .
The PAM Configuration of sshd . . .
Configuration of PAM Modules . . .
For More Information . . . . . . .
x
Xen Installation . . . . . . . . . .
Domain Installation . . . . . . . .
Configuring a Xen Guest Domain . . .
Starting and Controlling Xen Domains .
509
511
517
522
527
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . .
. . .
. . .
. . .
3 7 Virtualization with Xen
37.1
37.2
37.3
37.4
497
498
504
505
507
509
3 6 Authentication with PAM
36.1
36.2
36.3
36.4
492
492
493
493
494
497
3 5 The X Window System
35.1
35.2
35.3
35.4
486
487
487
489
489
489
528
529
532
534
535
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
537
537
540
542
37.5
For More Information . . . . . . . . . . . . . . . . . . . . . .
543
Part IX Services
545
3 8 Basic Networking
547
38.1
38.2
38.3
38.4
38.5
38.6
IP Addresses and Routing . . . . . . . . .
IPv6—The Next Generation Internet . . . .
Name Resolution . . . . . . . . . . . .
Configuring a Network Connection with YaST
Configuring a Network Connection Manually .
smpppd as Dial-up Assistant . . . . . . . .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3 9 SLP Services in the Network
39.1
39.2
39.3
39.4
Registering Your Own Services
SLP Front-Ends in SUSE Linux
Activating SLP . . . . . . .
For More Information . . .
589
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4 0 The Domain Name System
40.1
40.2
40.3
40.4
40.5
40.6
40.7
40.8
40.9
DNS Basics . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration with YaST . . . . . . . . . . . . . . . . . . . . . .
Starting the Name Server BIND . . . . . . . . . . . . . . . . . .
The Configuration File /etc/named.conf . . . . . . . . . . . . . . .
Zone Files . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dynamic Update of Zone Data . . . . . . . . . . . . . . . . . . .
Secure Transactions . . . . . . . . . . . . . . . . . . . . . . .
DNS Security . . . . . . . . . . . . . . . . . . . . . . . . . .
For More Information . . . . . . . . . . . . . . . . . . . . . .
Configuring NIS Servers Using YaST . . . . . . . . . . . . . . . . .
Configuring NIS Clients . . . . . . . . . . . . . . . . . . . . . .
Importing File Systems with YaST
Importing File Systems Manually
Exporting File Systems with YaST
Exporting File Systems Manually
593
593
601
603
607
611
611
613
613
615
4 2 Sharing File Systems with NFS
42.1
42.2
42.3
42.4
589
590
591
591
593
4 1 Using NIS
41.1
41.2
550
553
562
564
574
585
615
620
623
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
623
624
625
626
xi
4 3 DHCP
43.1
43.2
43.3
43.4
629
Configuring a DHCP Server with
DHCP Software Packages . . .
The DHCP Server dhcpd . . .
For More Information . . . .
YaST
. .
. .
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4 4 Time Synchronization with xntp
44.1
44.2
44.3
639
Configuring an NTP Client with YaST . . . . . . . . . . . . . . . .
Configuring xntp in the Network . . . . . . . . . . . . . . . . . .
Setting Up a Local Reference Clock . . . . . . . . . . . . . . . . .
4 5 LDAP—A Directory Service
45.1
45.2
45.3
45.4
45.5
45.6
45.7
LDAP versus NIS . . . . . . . . . . . .
Structure of an LDAP Directory Tree . . .
Server Configuration with slapd.conf . . .
Data Handling in the LDAP Directory . . .
The YaST LDAP Client . . . . . . . . . .
Configuring LDAP Users and Groups in YaST
For More Information . . . . . . . . .
Preface and Terminology
Installation . . . . . .
Configuration . . . . .
Virtual Hosts . . . . .
Apache Modules . . . .
Security . . . . . . .
Troubleshooting . . . .
For More Information .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
xii
647
648
651
656
660
668
669
671
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4 7 File Synchronization
47.1
47.2
47.3
47.4
47.5
47.6
47.7
639
642
643
645
4 6 The Apache Web Server
46.1
46.2
46.3
46.4
46.5
46.6
46.7
46.8
630
633
633
637
Available Data Synchronization Software . .
Determining Factors for Selecting a Program
Introduction to Unison . . . . . . . . .
Introduction to CVS . . . . . . . . . .
Introduction to Subversion . . . . . . .
Introduction to rsync . . . . . . . . . .
Introduction to mailsync . . . . . . . .
671
673
680
696
700
711
712
713
715
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
715
718
722
724
727
730
732
4 8 Samba
48.1
48.2
48.3
48.4
48.5
Configuring the Server . . . . . . .
Samba as Login Server . . . . . . .
Configuring a Samba Server with YaST .
Configuring Clients . . . . . . . . .
Optimization . . . . . . . . . . .
737
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
4 9 The Proxy Server Squid
49.1
49.2
49.3
49.4
49.5
49.6
49.7
49.8
49.9
Index
Some Facts about Proxy Caches . . . . .
System Requirements . . . . . . . . . .
Starting Squid . . . . . . . . . . . . .
The Configuration File /etc/squid/squid.conf
Configuring a Transparent Proxy . . . . .
cachemgr.cgi . . . . . . . . . . . . .
squidGuard . . . . . . . . . . . . . .
Cache Report Generation with Calamaris .
For More Information . . . . . . . . .
739
743
744
747
748
749
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
750
751
753
755
760
763
765
766
767
769
xiii
About This Guide
This manual gives you a general understanding of SUSE Linux. It is intended mainly
for system administrators and home users with basic system administration knowledge.
This manual presents a selection of applications needed in everyday life and provides
in-depth desciptions of advanced installation and configuration scenarios.
Advanced Deployment Scenarios
Learn how to deploy SUSE Linux in complex environments.
Internet, Multimedia, Office, and Graphics
Get a tour of the most important applications a home user might need.
Mobility
Get an introduction to mobile computing with SUSE Linux and learn how to configure the various options for wireless computing, power management, and profile
management.
Administration
Learn how to make your SUSE Linux secure, how to deal with file system access
controls, and get to know some important utilities for Linux administrators.
System
Get an introduction to the components of your Linux system and a deeper understanding of their interaction.
Services
Learn how to configure the various network and file services that come with SUSE
Linux.
1 Feedback
We want to hear your comments and suggestions about this manual and the other documentation included with this product. Please use the User Comments feature at the
bottom of each page of the online documentation, or go to http://www.novell
.com/documentation/feedback.html and enter your comments there.
2 Additional Documentation
There are other manuals available on this SUSE Linux product, either online at
http://www.novell.com/documentation/ or in your installed system under
/usr/share/doc/manual/:
Start-Up
This guide covers your first steps with SUSE Linux. An online version of this document can be found at http://www.novell.com/documentation/
suse10/.
Novell AppArmor Powered by Immunix 1.2 Installation and QuickStart Guide
This guide outlines the initial installation procedure for the AppArmor product. An
online version of this document can be found at http://www.novell.com/
documentation/apparmor/.
Novell AppArmor Powered by Immunix 1.2 Administration Guide
This guide contains in-depth information on the use of AppArmor in your environment. An online version of this document can be found at http://www.novell
.com/documentation/apparmor/.
3 Documentation Conventions
The following typographical conventions are used in this manual:
• /etc/passwd: filenames and directory names
• placeholder: replace placeholder with the actual value
• PATH: the environment variable PATH
• ls, --help: commands, options, and parameters
• user: users or groups
•
Alt
,
Alt
+
F1
: a key to press or a key combination
• File, File → Save As: menu items, buttons
xvi
• Dancing Penguins (Chapter Penguins, ↑Reference): This is a reference to a chapter
in another book.
4 Acknowledgment
With a lot of voluntary commitment, the developers of Linux cooperate on a global
scale to promote the development of Linux. We thank them for their efforts—this distribution would not exist without them. Furthermore, we thank Frank Zappa and Pawar.
Special thanks, of course, go to Linus Torvalds.
Have a lot of fun!
Your SUSE Team
About This Guide
xvii
Part I Advanced Deployment
Scenarios
1
Remote Installation
SUSE Linux can be installed in several different ways. As well as the usual CD or DVD
installation covered in Chapter Installation with YaST (↑Start-Up), you can choose from
various network-based approaches or even take a completely hands-off approach to the
installation of SUSE Linux.
Each method is introduced by means of two short check lists: one listing the prerequisites
for this method and the other illustrating the basic procedure. More detail is then provided for all the techniques used in these installation scenarios.
NOTE
In the following sections, the system to hold your new SUSE Linux installation
is referred to as target system or installation target. The term installation source
is used for all sources of installation data. This includes physical media, such
as CD and DVD, and network servers distributing the installation data in your
network.
1.1 Installation Scenarios for Remote
Installation
This section introduces the most common installation scenarios for remote installations.
For each scenario, carefully check the list of prerequisites and follow the procedure
outlined for this scenario. If in need of detailed instructions for a particular step, follow
the links provided for each one of them.
Remote Installation
21
IMPORTANT
The configuration of the X Window System is not part of any remote installation
process. After the installation has finished, log in to the target system as root,
enter init 3, and start SaX2 to configure the graphics hardware as described
in Section 35.1, “X11 Setup with SaX2” (page 509).
1.1.1 Simple Remote Installation via
VNC—Static Network Configuration
This type of installation still requires some degree of physical access to the target system
to boot for installation. The installation itself is entirely controlled by a remote workstation using VNC to connect to the installation program. User interaction is required as
with the manual installation in Chapter Installation with YaST (↑Start-Up).
For this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• Target system with working network connection
• Controlling system with working network connection and VNC viewer software
or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera)
• Physical boot medium (CD, or DVD) for booting the target system
• Valid static IP addresses already assigned to the installation source and the controlling system
• Valid static IP address to assign to the target system
To perform this kind of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30).
2 Boot the target system using the first CD or DVD of the SUSE Linux media kit.
22
3 When the boot screen of the target system appears, use the boot options prompt
to set the appropriate VNC options and the address of the installation source.
This is described in detail in Section 1.4, “Booting the Target System for Installation” (page 49).
The target system boots to a text-based environment, giving the network address
and display number under which the graphical installation environment can be
addressed by any VNC viewer application or browser. VNC installations announce
themselves over OpenSLP and can be found using Konqueror in service://
or slp:// mode.
4 On the controlling workstation, open a VNC viewing application or Web
browser and connect to the target system as described in Section 1.5.1, “VNC
Installation” (page 54).
5 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system after it reboots for the final part
of the installation.
6 Finish the installation.
1.1.2 Simple Remote Installation via
VNC—Dynamic Network
Configuration via DHCP
This type of installation still requires some degree of physical access to the target system
to boot for installation. The network configuration is made with DHCP. The installation
itself is entirely controlled from a remote workstation using VNC to connect to the installer, but still requires user interaction for the actual configuration efforts.
For this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• Target system with working network connection
Remote Installation
23
• Controlling system with working network connection and VNC viewer software
or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera)
• Physical boot medium (CD, DVD, custom boot disk) for booting the target system
• Running DHCP server providing IP addresses
To perform this kind of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30). Choose an NFS, HTTP, or FTP
network server. For a SMB installation source, refer to Section 1.2.5, “Managing
a SMB Installation Source” (page 38).
2 Boot the target system using the first CD or DVD of the SUSE Linux media kit.
3 When the boot screen of the target system appears, use the boot options prompt
to set the appropriate VNC options and the address of the installation source.
This is described in detail in Section 1.4, “Booting the Target System for Installation” (page 49).
The target system boots to a text-based environment, giving the network address
and display number under which the graphical installation environment can be
addressed by any VNC viewer application or browser. VNC installations announce
themselves over OpenSLP and can be found using Konqueror in service://
or slp:// mode.
4 On the controlling workstation, open a VNC viewing application or Web
browser and connect to the target system as described in Section 1.5.1, “VNC
Installation” (page 54).
5 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system after it reboots for the final part
of the installation.
6 Finish the installation.
24
1.1.3 Remote Installation via VNC—PXE
Boot and Wake on LAN
This type of installation is completely hands-off. The target machine is started and
booted remotely. User interaction is only needed for the actual installation. This approach
is suitable for cross-site deployments.
To perform this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• TFTP server
• Running DHCP server for your network
• Target system capable of PXE boot, networking, and Wake on LAN, plugged in
and connected to the network
• Controlling system with working network connection and VNC viewer software
or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera)
To perform this type of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30). Choose an NFS, HTTP, FTP network
server or configure a SMB installation source as described in Section 1.2.5,
“Managing a SMB Installation Source” (page 38).
2 Set up a TFTP server to hold a boot image that can be pulled by the target system.
This is described in Section 1.3.2, “Setting Up a TFTP Server” (page 41).
3 Set up a DHCP server to provide IP addresses to all machines and reveal the location of the TFTP server to the target system. This is described in Section 1.3.1,
“Setting Up a DHCP Server” (page 40).
4 Prepare the target system for PXE boot. This is described in further detail in
Section 1.3.5, “Preparing the Target System for PXE Boot” (page 48).
Remote Installation
25
5 Initiate the boot process of the target system using Wake on LAN. This is described in Section 1.3.7, “Wake on LAN” (page 48).
6 On the controlling workstation, open a VNC viewing application or Web
browser and connect to the target system as described in Section 1.5.1, “VNC
Installation” (page 54).
7 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system after it reboots for the final part
of the installation.
8 Finish the installation.
1.1.4 Simple Remote Installation via
SSH—Static Network Configuration
This type of installation still requires some degree of physical access to the target system
to boot for installation and to determine the IP address of the installation target. The
installation itself is entirely controlled from a remote workstation using SSH to connect
to the installer. User interaction is required as with the regular installation described in
Chapter Installation with YaST (↑Start-Up).
For this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• Target system with working network connection
• Controlling system with working network connection and VNC viewer software
or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera)
• Physical boot medium (CD, DVD, custom boot disk) for the target system
• Valid static IP addresses already assigned to the installation source and the controlling system
26
• Valid static IP address to assign to the target system
To perform this kind of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30).
2 Boot the target system using the first CD or DVD of the SUSE Linux media kit.
3 When the boot screen of the target system appears, use the boot options prompt
to set the appropriate parameters for network connection, address of the installation source, and SSH enablement. This is described in detail in Section 1.4.3,
“Using Custom Boot Options” (page 51).
The target system boots to a text-based environment, giving the network address
under which the graphical installation environment can be addressed by any SSH
client.
4 On the controlling workstation, open a terminal window and connect to the target
system as described in Section “Connecting to the Installation Program”
(page 56).
5 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system after it reboots for the final part
of the installation.
6 Finish the installation.
1.1.5 Simple Remote Installation via
SSH—Dynamic Network Configuration
via DHCP
This type of installation still requires some degree of physical access to the target system
to boot for installation and determine the IP address of the installation target. The installation itself is entirely controlled from a remote workstation using VNC to connect to
the installer, but still requires user interaction for the actual configuration efforts.
Remote Installation
27
For this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• Target system with working network connection
• Controlling system with working network connection and VNC viewer software
or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera)
• Physical boot medium (CD or DVD) for booting the target system
• Running DHCP server providing IP addresses
To perform this kind of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30). Choose an NFS, HTTP, or FTP
network server. For a SMB installation source, refer to Section 1.2.5, “Managing
a SMB Installation Source” (page 38).
2 Boot the target system using the first CD or DVD of the SUSE Linux media kit.
3 When the boot screen of the target system appears, use the boot options prompt
to pass the appropriate parameters for network connection, location of the installation source, and SSH enablement. See Section 1.4.3, “Using Custom Boot
Options” (page 51) for detailed instructions on the use of these parameters.
The target system boots to a text-based environment, giving you the network
address under which the graphical installation environment can be addressed by
any SSH client.
4 On the controlling workstation, open a terminal window and connect to the target
system as described in Section “Connecting to the Installation Program”
(page 56).
5 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system after it reboots for the final part
of the installation.
28
6 Finish the installation.
1.1.6 Remote Installation via SSH—PXE
Boot and Wake on LAN
This type of installation is completely hands-off. The target machine is started and
booted remotely.
To perform this type of installation, make sure that the following requirements are met:
• Remote installation source: NFS, HTTP, FTP, or SMB with working network
connection
• TFTP server
• Running DHCP server for your network, providing a static IP to the host to install
• Target system capable of PXE boot, networking, and Wake on LAN, plugged in
and connected to the network
• Controlling system with working network connection and SSH client software
To perform this type of installation, proceed as follows:
1 Set up the installation source as described in Section 1.2, “Setting Up the Server
Holding the Installation Sources” (page 30). Choose an NFS, HTTP, or FTP
network server. For the configuration of a SMB installation source, refer to
Section 1.2.5, “Managing a SMB Installation Source” (page 38).
2 Set up a TFTP server to hold a boot image that can be pulled by the target system.
This is described in Section 1.3.2, “Setting Up a TFTP Server” (page 41).
3 Set up a DHCP server to provide IP addresses to all machines and reveal the location of the TFTP server to the target system. This is described in Section 1.3.1,
“Setting Up a DHCP Server” (page 40).
4 Prepare the target system for PXE boot. This is described in further detail in
Section 1.3.5, “Preparing the Target System for PXE Boot” (page 48).
Remote Installation
29
5 Initiate the boot process of the target system using Wake on LAN. This is described in Section 1.3.7, “Wake on LAN” (page 48).
6 On the controlling workstation, start a VNC client and connect to the target system
as described in Section 1.5.2, “SSH Installation” (page 55).
7 Perform the installation as described in Chapter Installation with YaST (↑StartUp).
You will need to reconnect to the target system it reboots for the final part of the
installation.
8 Finish the installation.
1.2 Setting Up the Server Holding
the Installation Sources
Depending on the operating system running on the machine to use as network installation
source for SUSE Linux, there are several options for the server configuration. The
easiest way to set up an installation server is to use YaST on SUSE LINUX Enterprise
Server 9 or SUSE Linux 9.3 and higher. On other versions of SUSE LINUX Enterprise
Server or SUSE Linux, set up the installation source manually.
TIP
You can even use a Microsoft Windows machine as installation server for your
Linux deployment. See Section 1.2.5, “Managing a SMB Installation Source”
(page 38) for details.
1.2.1 Setting Up an Installation Server
Using YaST
YaST offers a graphical tool for creating network installation sources. It supports HTTP,
FTP, and NFS network installation servers.
1 Log in as root to the machine that should act as installation server.
30
2 Start YaST → Miscellaneous → Installation Server.
3 Select the server type (HTTP, FTP, or NFS).
The selected server service is started automatically every time the system starts.
If a service of the selected type is already running on your system and you want
to configure it manually for the server, deactivate the automatic configuration of
the server service with Do not configure any network services. In both cases,
define the directory in which the installation data should be made available on
the server.
4 Configure the required server type.
This step relates to the automatic configuration of server services. It is skipped
when automatic configuration is deactivated. Define an alias for the root directory
of the FTP or HTTP server on which the installation data should be found. The
installation source will later be located under
ftp://Server-IP/Alias/Name (FTP) or under
http://Server-IP/Alias/Name (HTTP). Name stands for the name of
the installation source, which is defined in the following step. If you selected
NFS in the previous step, define wild cards and exports options. The NFS server
will be accessible under nfs://Server-IP/Name. Details of NFS and exports
can be found in Chapter 42, Sharing File Systems with NFS (page 623).
5 Configure the installation source.
Before the installation media are copied to their destination, define the name of
the installation source (ideally, an easily remembered abbreviation of the product
and version). YaST allows providing ISO images of the media instead of copies
of the installation CDs. If you want this, activate the relevant check box and
specify the directory path under which the ISO files can be found locally. Depending on the product to distribute using this installation server, it might be that
more add-on CDs or service pack CDs are required to install the product completely. If you activate Prompt for Additional CDs, YaST automatically reminds
you to supply these media. To announce your installation server in the network
via OpenSLP, activate the appropriate option.
Remote Installation
31
TIP
Consider announcing your installation source via OpenSLP if your network
setup supports this option. This saves you from entering the network installation path on every target machine. The target systems are just
booted using the SLP boot option and will find the network installation
source without any further configuration. For details on this option, refer
to Section 1.4, “Booting the Target System for Installation” (page 49).
6 Upload the installation data.
The most lengthy step in configuring an installation server is copying the actual
installation CDs. Insert the media in the sequence requested by YaST and wait
for the copying procedure to end. When the sources have been fully copied, return
to the overview of existing information sources and close the configuration by
selecting Finish.
Your installation server is now fully configured and ready for service. It is automatically started every time the system is started. No further intervention is required. You only need to configure and start this service correctly by hand if you
have deactivated the automatic configuration of the selected network service
with YaST as an initial step.
To deactivate an installation source, select Change in the overview to reach a list of all
available installation sources. Choose the entry to remove then select Delete. This delete
procedure only relates to the deactivation of the server service. The installation data itself
remains in the directory chosen. However, you can remove it manually.
If your installation server should provide the installation data for more than one product
of product version, start the YaST installation server module and select Configure in
the overview of existing installation sources to configure the new installation source.
1.2.2 Manual Setup of an NFS Installation
Source
Setting up an NFS source for installation is basically done in two steps. In the first step,
create the directory structure holding the installation data and copy the installation
32
media over to this structure. Second, export the directory holding the installation data
to the network.
To create a directory holding the installation data, proceed as follows:
1 Log in as root.
2 Create a directory that should later hold all installation data and change into this
directory. For example:
mkdir install/product/productversion
cd install/product/productversion
Replace product with an abbreviation of the product name (in this case SUSE
Linux) and productversion with a string that contains the product name
and version.
3 For each CD contained in the media kit execute the following commands:
a Copy the entire content of the installation CD into the installation server
directory:
cp -a /media/path_to_your_CD-ROM_drive .
Replace path_to_your_CD-ROM_drive with the actual path under
which your CD or DVD drive is addressed. Depending on the type of drive
used in your system, this can be cdrom, cdrecorder, dvd, or
dvdrecorder.
b Rename the directory to the CD number:
mv path_to_your_CD-ROM_drive CDx
Replace x with the actual number of your CD.
To export the installation sources via NFS using YaST, proceed as follows:
1 Log in as root.
2 Start YaST → Network Services → NFS Server.
3 Select Start NFS Server and Open Port in Firewall and click Next.
Remote Installation
33
4 Select Add Directory and enter the path to the directory holding the installation
data. In this case, it is /productversion.
5 Select Add Host and enter the hostnames of the machines to which to export the
installation data. Instead of specifying hostnames here, you could also use wild
cards, ranges of network addresses, or just the domain name of your network.
Enter the appropriate export options or leave the default, which works fine in
most setups. For more information about the syntax used in exporting NFS shares,
read the exports man page.
6 Click Finish.
The NFS server holding the SUSE Linux installation sources is automatically
started and integrated into the boot process.
If you prefer to manually export the installation sources via NFS instead of using the
YaST NFS Server module, proceed as follows:
1 Log in as root.
2 Open the file /etc/exports and enter the following line:
/productversion *(ro,root_squash,sync)
This exports the directory /productversion to any host that is part of this
network or to any host that can connect to this server. To limit the access to this
server, use netmasks or domain names instead of the general wild card *. Refer
to the export man page for details. Save and exit this configuration file.
3 To add the NFS service to the list of servers started during system boot, execute
the following commands:
insserv /etc/init.d/nfsserver
insserv /etc/init.d/portmap
4 Start the NFS server using the following command:
rcnfsserver start
If you need to change the configuration of your NFS server later, modify the
configuration file and restart the NFS daemon with rcnfsserver restart.
34
Announcing the NFS server via OpenSLP makes its address known to all clients in
your network.
1 Log in as root.
2 Enter the directory /etc/slp.reg.d/.
3 Create a configuration file called install.suse.nfs.reg containing the
following lines:
# Register the NFS Installation Server
service:install.suse:nfs://$HOSTNAME/path_instsource/CD1,en,65535
description=NFS Installation Source
Replace path_instsource with the actual path to the installation source on
your server.
4 Save this configuration file and start the OpenSLP daemon using the following
command:
rcslpd start
For more information about OpenSLP, refer to the package documentation located under
/usr/share/doc/packages/openslp/ or refer to Chapter 39, SLP Services
in the Network (page 589).
1.2.3 Manual Setup of an FTP Installation
Source
Creating an FTP installation source is very similar to creating an NFS installation source.
FTP installation sources can be announced over the network using OpenSLP as well.
1 Create a directory holding the installation sources as described in Section 1.2.2,
“Manual Setup of an NFS Installation Source” (page 32).
2 Configure the FTP server to distribute the contents of your installation directory:
a Log in as root and install the package pure-ftpd (a lean FTP server) using
the YaST package manager.
b Enter the FTP server root directory:
Remote Installation
35
cd/srv/ftp
c Create a subdirectory holding the installation sources in the FTP root directory:
mkdir instsource
Replace instsource with the product name.
d Copy the contents of all installation CDs into the FTP server's root directory
(similar to the procedure described in Section 1.2.2, “Manual Setup of an
NFS Installation Source” (page 32), Step 3 (page 33)).
Alternatively, mount the contents of the already existing installation repository into the change root environment of the FTP server:
mount --bind path_to_instsource /srv/ftp/instsource
Replace path_to_instsource and instsource with values
matching your setup. If you need to make this permanent, add it to /etc/
fstab.
e Start pure-ftpd:
pure-ftpd &
3 Announce the installation source via OpenSLP, if this is supported by your network setup:
a Create a configuration file called install.suse.ftp.reg under /etc/
slp/reg.d/ that contains the following lines:
# Register the FTP Installation Server
service:install.suse:ftp://$HOSTNAME/srv/ftp/instsource/CD1,en,65535
description=FTP Installation Source
Replace instsource with the actual name to the installation source directory on your server. The service: line should be entered as one continuous
line.
b Save this configuration file and start the OpenSLP daemon using the following command:
rcslpd start
36
1.2.4 Manual Setup of an HTTP Installation
Source
Creating an HTTP installation source is very similar to creating an NFS installation
source. HTTP installation sources can be announced over the network using OpenSLP
as well.
1 Create a directory holding the installation sources as described in Section 1.2.2,
“Manual Setup of an NFS Installation Source” (page 32).
2 Configure the HTTP server to distribute the contents of your installation directory:
a Log in as root and install the package apache2 using the YaST package
manager.
b Enter the root directory of the HTTP server (/srv/www/htdocs) and
create a subdirectory that will hold the installation sources:
mkdir instsource
Replace instsource with the product name.
c Create a symbolic link from the location of the installation sources to the
root directory of the Web server (/srv/www/htdocs):
ln -s /path_instsource /srv/www/htdocs/instsource
d Modify the configuration file of the HTTP server (/etc/apache2/
default-server.conf) to make it follow symbolic links. Replace the
following line:
Options None
with
Options Indexes FollowSymLinks
e Restart the HTTP server using rcapache2 restart.
Remote Installation
37
3 Announce the installation source via OpenSLP, if this is supported by your network setup:
a Create a configuration file called install.suse.http.reg under
/etc/slp/reg.d/ that contains the following lines:
# Register the HTTP Installation Server
service:install.suse:http://$HOSTNAME/srv/www/htdocs/instsource/CD1/,en,65535
description=HTTP Installation Source
Replace path_to_instsource with the actual path to the installation
source on your server. The service: line should be entered as one continuous line.
b Save this configuration file and start the OpenSLP daemon using rcslpd
restart.
1.2.5 Managing a SMB Installation Source
Using SMB (Samba), you can import the installation sources from a Microsoft Windows
server and start your Linux deployment even with no Linux machine around.
To set up an exported Windows Share holding your SUSE Linux installation sources,
proceed as follows:
1 Log in to your Windows machine.
2 Start Explorer and create a new folder that will hold the entire installation tree
and name it INSTALL, for example.
3 Export this share according the procedure outlined in your Windows documentation.
4 Enter this share and create a subfolder, called product. product needs to be
replaced with the actual product name (SUSE Linux in this case).
5 Copy each SUSE Linux CD into a separate folder and name these folders CD1,
CD2, CD3, etc.
38
6 Enter the top directory of the exported share (INSTALL, in this example) and
copy the following files and folders from product/CD1 to this folder:
content, media.1, control.xml, and boot.
7 Create a new folder under INSTALL and name it yast.
Enter the yast folder and create the files order and instorder.
8 Open the order file and enter the following line:
/NLD/CD1 smb://user:[email protected]/productCD1
Replace user with the username you use on the Windows machine or use Guest
to enable guest login to this share. password should be replaced either with
your login password or any other string for guest login. hostname should be
replaced with the network name of your Windows machine.
9 Open the instorder file and add the following line:
/product/CD1
To use a SMB mounted share as installation source, proceed as follows:
1 Boot the installation target.
2 Select Installation.
3 Press
F4
for a selection of installation sources.
4 Choose SMB and enter the Windows machine's name or IP address, the share
name (INSTALL, in this example), username, and password.
After you hit
Enter
, YaST starts and you can perform the installation.
Remote Installation
39
1.3 Preparing the Boot of the Target
System
This section covers the configuration tasks needed in complex boot scenarios. It contains
ready-to-apply configuration examples for DHCP, PXE boot, TFTP, and Wake on
LAN.
1.3.1 Setting Up a DHCP Server
The setup of a DHCP server on SUSE Linux is done by manually editing the appropriate
configuration files. This section covers extending an existing DHCP server configuration
to provide the data needed to serve in a TFTP, PXE, and WOL environment.
Manual Setup of a DHCP Server
All the DHCP server needs to do, apart from providing automatic address allocation to
your network clients, is to announce the IP address of the TFTP server and the file that
should be pulled in by the installation routines on the target machine.
1 Log in as root to the machine hosting the DHCP server.
2 Append the following lines to your DHCP server's configuration file located
under /etc/dhcpd.conf:
group {
# PXE related stuff
#
# "next server" defines the tftp server that will be used
next server ip_tftp_server:
#
# "filename" specifiies the pxelinux image on the tftp server
# the server runs in chroot under /srv/tftpboot
filename "pxelinux.0";
}
Replace ip_of_the_tftp_server with the actual IP address of the TFTP
server.
For more information about the options available in dhcpd.conf, refer to the
dhcpd.conf manual page.
40
3 Restart the DHCP server by executing rcdhcpd restart.
If you plan on using SSH for the remote control of a PXE and Wake on LAN installation,
explicitly specify the IP address DHCP should provide to the installation target. To
achieve this, modify the above mentioned DHCP configuration according to the following example:
group {
# PXE related stuff
#
# "next server" defines the tftp server that will be used
next server ip_tftp_server:
#
# "filename" specifiies the pxelinux image on the tftp server
# the server runs in chroot under /srv/tftpboot
filename "pxelinux.0";
host test { hardware ethernet mac_address;
fixed-address some_ip_address; }
}
The host statement introduces the hostname of the installation target. To bind the
hostname and IP address to a specific host, you have to know and specify the system's
hardware (MAC) address. Replace all the variables used in this example with the actual
values that match your environment.
After restarting the DHCP server, it provides a static IP to the host specified, enabling
you to connect to the system via SSH.
1.3.2 Setting Up a TFTP Server
Set up a TFTP server with YaST or manually on any other Linux operating system that
supports xinetd and tftp. The TFTP server delivers the boot image to the target system
once it boots and sends a request for it.
Setting Up a TFTP Server Using YaST
1 Log in as root.
2 Start YaST → Network Services → TFTP Server and install the requested package.
Remote Installation
41
3 Click Enable to make sure that the server is started and included in the boot
routines. No further action from your side is required to secure this. xinetd starts
tftpd at boot time.
4 Click Open Port in Firewall to open the appropriate port in the firewall running
on your machine. If there is no firewall running on your server, this option is not
available.
5 Click Browse to browse for the boot image directory.
The default directory /tftpboot is created and selected automatically.
6 Click Finish to apply your settings and start the server.
Manual Setup of a TFTP Server
1 Log in as root and install the packages tftp and xinetd.
2 If unavailable, create /srv/tftpboot and /srv/tftpboot/pxelinux
.cfg directories.
3 Add the appropriate files needed for the boot image as described in Section 1.3.3,
“PXE Boot” (page 43).
4 Modify the configuration of xinetd located under /etc/xinetd.d/ to make
sure that the tftp server is started on boot:
a If it does not exist, create a file called tftp under this directory with touch
tftp. Then run chmod 755 tftp.
b Open the file tftp and add the following lines:
service tftp
{
socket_type
protocol
wait
user
server
server_args
disable
}
42
=
=
=
=
=
=
=
dgram
udp
yes
root
/usr/sbin/in.tftpd
-s /tftpboot
no
c Save the file and restart xinetd with rcxinetd restart.
1.3.3 PXE Boot
Some technical background information as well as PXE's complete specifications are
available in the Preboot Execution Environment (PXE) Specification (ftp://
download.intel.com/labs/manage/wfm/download/pxespec.pdf).
1 Change to the directory of your installation repository and copy the linux,
initrd, message, and memtest files to the /srv/tftpboot directory
by entering the following:
cp -a boot/loader/linux boot/loader/initrd
boot/loader/message boot/loader/memtest /srv/tftpboot
2 Install the syslinux package directly from your installation CDs or DVDs
with YaST.
3 Copy the /usr/share/syslinux/pxelinux.0 file to the /srv/
tftpboot directory by entering the following:
cp -a /usr/share/syslinux/pxelinux.0 /srv/tftpboot
4 Change to the directory of your installation repository and copy the isolinux
.cfg file to /srv/tftpboot/pxelinux.cfg/default by entering the
following:
cp -a boot/loader/isolinux.cfg /srv/tftpboot/pxelinux.cfg/default
5 Edit the /srv/tftpboot/pxelinux.cfg/default file and remove the
lines beginning with gfxboot, readinfo, and framebuffer.
6 Insert the following entries in the append lines of the default failsafe and
apic labels:
insmod=e100
By means of this entry, the kernel module for an Intel 100MBit/s network
card is loaded on the PXE clients. This entry depends on the client's hardware
Remote Installation
43
and must be adapted accordingly. In the case of a Broadcom GigaBit network
card, this entry should read insmod=bcm5700.
netdevice=eth0
This entry defines the client's network interface that must be used for the
network installation. It is only necessary if the client is equipped with several
network cards and must be adapted accordingly. In case of a single network
card, this entry can be omitted.
install=nfs://ip_instserver/path_instsource/CD1
This entry defines the NFS server and the installation source for the client
installation. Replace ip_instserver with the actual IP address of your
installation server. path_instsource should be replaced with the actual
path to the installation sources. HTTP, FTP, or SMB sources are addressed
in a similar manner, except for the protocol prefix, which should read http,
ftp, or smb.
IMPORTANT
If you need to pass other boot options to the installation routines,
such as SSH or VNC boot parameters, append them to the install
entry. An overview of parameters and some examples are given in
Section 1.4, “Booting the Target System for Installation” (page 49).
An example /srv/tftpboot/pxelinux.cfg/default file follows.
Adjust the protocol prefix for the installation source to match your network setup
and specify your preferred method of connecting to the installer by adding the
vnc and vncpassword or the ssh and sshpassword options to the
install entry. The lines separated by \ must be entered as one continuous
line without a line break and without the \.
default linux
# default
label linux
kernel linux
append initrd=initrd ramdisk_size=65536 insmod=e100 \
install=nfs://ip_instserver/path_instsource/product
# failsafe
label failsafe
kernel linux
append initrd=initrd ramdisk_size=65536 ide=nodma apm=off acpi=off \
44
insmod=e100 install=nfs://ip_instserver/path_instsource/product
# apic
label apic
kernel linux
append initrd=initrd ramdisk_size=65536 apic insmod=e100 \
install=nfs://ip_instserver/path_instsource/product
# manual
label manual
kernel linux
append initrd=initrd ramdisk_size=65536 manual=1
# rescue
label rescue
kernel linux
append initrd=initrd ramdisk_size=65536 rescue=1
# memory test
label memtest
kernel memtest
# hard disk
label harddisk
kernel
linux append SLX=0x202
implicit
display
prompt
timeout
0
message
1
100
Replace ip_instserver and path_instsource with the values used in
your setup.
The following section serves as a short reference to the PXELINUX options used
in this setup. More information about the options available can be found in the
documentation of the syslinux package located under /usr/share/doc/
packages/syslinux/.
1.3.4 PXELINUX Configuration Options
The options listed here are a subset of all the options available for the PXELINUX
configuration file.
Remote Installation
45
DEFAULT kernel options...
Sets the default kernel command line. If PXELINUX boots automatically, it acts
as if the entries after DEFAULT had been typed in at the boot prompt, except the
auto option is automatically added, indicating an automatic boot.
If no configuration file is present or no DEFAULT entry is present in the configuration file, the default is the kernel name “linux” with no options.
APPEND options...
Add one or more options to the kernel command line. These are added for both automatic and manual boots. The options are added at the very beginning of the kernel
command line, usually permitting explicitly entered kernel options to override them.
LABEL label KERNEL image APPEND options...
Indicates that if label is entered as the kernel to boot, PXELINUX should instead
boot image and the specified APPEND options should be used instead of the ones
specified in the global section of the file (before the first LABEL command). The
default for image is the same as label and, if no APPEND is given, the default
is to use the global entry (if any). Up to 128 LABEL entries are permitted.
Note that GRUB uses the following syntax:
title mytitle
kernel my_kernel my_kernel_options
initrd myinitrd
while PXELINUX uses the following syntax:
label mylabel
kernel mykernel
append myoptions
Labels are mangled as if they were filenames and they must be unique after mangling.
For example, the two labels “v2.1.30” and “v2.1.31” would not be distinguishable
under PXELINUX because both mangle to the same DOS filename.
The kernel does not have to be a Linux kernel; it can be a boot sector or a COMBOOT file.
APPEND Append nothing. APPEND with a single hyphen as argument in a LABEL section
can be used to override a global APPEND.
46
LOCALBOOT type
On PXELINUX, specifying LOCALBOOT 0 instead of a KERNEL option means
invoking this particular label and causes a local disk boot instead of a kernel boot.
Argument
Description
0
Perform a normal boot
4
Performs a local boot with the Universal
Network Driver Interface (UNDI) driver still
resident in memory
5
Performs a local boot with the entire PXE
stack, including the UNDI driver, still resident in memory
All other values are undefined. If you do not know what the UNDI or PXE stacks
are, specify 0.
TIMEOUT time-out
Indicates how long to wait at the boot prompt until booting automatically, in units
of 1/10 second. The time-out is cancelled as soon as the user types anything on the
keyboard, the assumption being that the user completes the command begun. A
time-out of zero disables the time-out completely (this is also the default).
The maximum possible time-out value is 35996 (just less than one hour).
PROMPT flag_val
If flag_val is 0, displays the boot prompt only if Shift or Alt is pressed or Caps
Lock or Scroll lock is set (this is the default). If flag_val is 1, always displays the
boot prompt.
F2 filename
F1 filename
..etc...
F9 filename
F10filename
Displays the indicated file on the screen when a function key is pressed at the boot
prompt. This can be used to implement preboot online help (presumably for the
kernel command line options.) For backward compatibility with earlier releases,
Remote Installation
47
F10
to
can be also entered as
and F12 .
F0
. Note that there is currently no way to bind filenames
F11
1.3.5 Preparing the Target System for PXE
Boot
Prepare the system's BIOS for PXE boot by including the PXE option in the BIOS boot
order.
WARNING
Do not place the PXE option ahead of the hard disk boot option in the BIOS.
Otherwise this system would try to reinstall itself every time you boot it.
1.3.6 Preparing the Target System for Wake
on LAN
Wake on LAN (WOL) requires the appropriate BIOS option to be enabled prior to the
installation. Also, note down the MAC address of the target system. This data is needed
to initiate Wake on LAN.
1.3.7 Wake on LAN
Wake on LAN allows a machine to be powered on via a special network packet that is
sent containing the machine's MAC address. Because every machine in the world has
a unique MAC identifier, you do not need to worry about accidentally powering on the
wrong machine.
IMPORTANT
If the controlling machine is not located in the same network segment as the
installation target that should be awakened, either configure the WOL requests
to be sent as multicasts or remotely control a machine on that network segment
to act as the sender of these requests.
48
1.3.8 Manual Wake on LAN
1 Log in as root.
2 Start YaST → Software Management and install the package netdiag.
3 Open a terminal and enter the following command as root to wake the target:
ether-wakemac_of_target
Replace mac_of_target with the actual MAC address of the target.
1.4 Booting the Target System for
Installation
Basically, there are two different ways to customize the boot process for installation
apart from those mentioned under Section 1.3.7, “Wake on LAN” (page 48) and Section 1.3.3, “PXE Boot” (page 43). You can either use the default boot options and F
keys or use the boot options prompt of the installation boot screen to pass any boot
options that the installation kernel might need on this particular hardware.
1.4.1 Using the Default Boot Options
The boot options have already been described in detail in Chapter Installation with
YaST (↑Start-Up).
Generally, just selecting Installation starts the installation boot process. If problems
occur, the Installation—ACPI Disabled or Installation—Safe Settings options might
come in handy.
For more information about troubleshooting the installation process, refer to Section “Installation Problems” (Chapter 9, Common Problems and Their Solutions, ↑Start-Up).
Remote Installation
49
1.4.2 Using the F Keys
The menu bar at the bottom screen offers some advanced functionality needed in some
setups. Using the F keys, you can specify additional options to pass to the installation
routines without having to know the detailed syntax of these parameters you would
need if you entered them as boot options (see Section 1.4.3, “Using Custom Boot Options” (page 51)).
See the table below for a complete set of the options available.
Table 1.1
Key
F Keys During Installation
Purpose
Available Options
Default Value
F1
Provide help
None
None
F2
Select the installation
language
All supported languages
English
F3
Change screen resolution
for installation
• Text mode
• VESA
• resolution #1
• Default value
depends on
your graphics
hardware
• resolution #2
• ...
F4
Select the installation
source
• CD-ROM/DVD
• SLP
• FTP
• HTTP
• NFS
• SMB
50
CD-ROM/DVD
Key
Purpose
Available Options
Default Value
• Hard Disk
F5
Apply driver update disk Driver
None
1.4.3 Using Custom Boot Options
Using the appropriate set of boot options helps facilitate your installation procedure.
Many parameters can also be configured later using the linuxrc routines, but using the
boot options is easier. In some automated setups, the boot options can be provided with
initrd or an info file.
The following table lists all installation scenarios mentioned in this chapter with the
required parameters for booting and the corresponding boot options. Just append all of
them in the order they appear in this table to get one boot option string that is handed
to the installation routines. For example (all in one line):
install=... netdevice=... hostip=...netmask=... vnc=... vncpassword=...
Replace all the values (...) in this string with the values appropriate for your setup.
Table 1.2
Installation (Boot) Scenarios Used in This Chapter
Installation Scenario
Parameters Needed
for Booting
Boot Options
Chapter Installation with None: system boots au- None needed
tomatically
YaST (↑Start-Up)
Section 1.1.1, “Simple
Remote Installation via
VNC—Static Network
Configuration” (page 22)
• Location of the installation server
• Network device
• IP address
• Netmask
• Gateway
• VNC enablement
• VNC password
• install=(nfs,http,
ftp,smb)://path_to
_instmedia
• netdevice=some
_netdevice (only needed if several network devices are available)
Remote Installation
51
Installation Scenario
Parameters Needed
for Booting
Boot Options
• hostip=some_ip
• netmask=some
_netmask
• gateway=ip_gateway
• vnc=1
• vncpassword=some
_password
52
Section 1.1.2, “Simple
Remote Installation via
VNC—Dynamic Network Configuration via
DHCP” (page 23)
• Location of the installation server
• VNC enablement
• VNC password
Section 1.1.3, “Remote
Installation via
VNC—PXE Boot and
Wake on LAN”
(page 25)
• Location of the installation server
• Location of the
TFTP server
• VNC enablement
• VNC password
Section 1.1.4, “Simple
Remote Installation via
SSH—Static Network
Configuration” (page 26)
• Location of the installation server
• Network device
• IP address
• Netmask
• Gateway
• SSH enablement
• SSH password
• install=(nfs,http,
ftp,smb)://path_to
_instmedia
• vnc=1
• vncpassword=some
_password
Not applicable; process managed through PXE and DHCP
• install=(nfs,http,
ftp,smb)://path_to
_instmedia
• netdevice=some
_netdevice (only needed if several network devices are available)
• hostip=some_ip
• netmask=some
_netmask
• gateway=ip_gateway
Installation Scenario
Parameters Needed
for Booting
Boot Options
• usessh=1
• sshpassword=some
_password
Section 1.1.5, “Simple
Remote Installation via
SSH—Dynamic Network
Configuration via
DHCP” (page 27)
• Location of the installation server
• SSH enablement
• SSH password
Section 1.1.6, “Remote
Installation via
SSH—PXE Boot and
Wake on LAN”
(page 29)
• Location of the installation server
• Location of the
TFTP server
• SSH enablement
• SSH password
• install=(nfs,http,
ftp,smb)://path_to
_instmedia
• usessh=1
• sshpassword=some
_password
Not applicable; process managed through PXE and DHCP
TIP
Find more information about the linuxrc boot options used for booting a Linux
system in /usr/share/doc/packages/linuxrc/linuxrc.html.
1.5 Monitoring the Installation
Process
There are several options for remotely monitoring the installation process. If the proper
boot options have been specified while booting for installation, either VNC or SSH can
be used to control the installation and system configuration from a remote workstation.
Remote Installation
53
1.5.1 VNC Installation
Using any VNC viewer software, you can remotely control the installation of SUSE
Linux from virtually any operating system. This section introduces the setup using a
VNC viewer application or a Web browser.
Preparing for VNC Installation
All you need to do on the installation target to prepare for a VNC installation is to
provide the appropriate boot options at the initial boot for installation (see Section 1.4.3,
“Using Custom Boot Options” (page 51)). The target system boots into a text-based
environment and waits for a VNC client to connect to the installation program.
The installation program announces the IP address and display number needed to connect
for installation. If you have physical access to the target system, this information is
provided right after the system booted for installation. Enter this data when your VNC
client software prompts for it and provide your VNC password.
Because the installation target announces itself via OpenSLP, you can retrieve the address
information of the installation target via an SLP browser without the need for any
physical contact to the installation itself provided your network setup and all machines
support OpenSLP:
1 Start the KDE file and Web browser Konqueror.
2 Enter service://yast.installation.suse in the location bar.
The target system then appears as an icon in the Konqueror screen. Clicking this
icon launches the KDE VNC viewer in which to perform the installation. Alternatively, run your VNC viewer software with the IP address provided and add
:1 at the end of the IP address for the display the installation is running on.
Connecting to the Installation Program
Basically, there are two ways to connect to a VNC server (the installation target in this
case). You can either start an independent VNC viewer application on any operating
system or connect using a Java-enabled Web browser.
54
Using VNC, you can control the installation of a Linux system from any other operating
system, including other Linux flavors, Windows, or Mac OS.
On a Linux machine, make sure that the package tightvnc is installed. On a Windows
machine, install the Windows port of this application, which can be obtained at the
TightVNC home page (http://www.tightvnc.com/download.html).
To connect to the installation program running on the target machine, proceed as
follows:
1 Start the VNC viewer.
2 Enter the IP address and display number of the installation target as provided by
the SLP browser or the installation program itself:
ip_address:display_number
A window opens on your desktop displaying the YaST screens as in a normal
local installation.
Using a Web browser to connect to the installation program makes you totally independent of any VNC software or the underlying operating system. As long as the browser
application has Java support enabled, you can use any browser (Firefox, Internet Explorer, Konqueror, Opera, etc.) to perform the installation of your Linux system.
To perform a VNC installation, proceed as follows:
1 Launch your preferred Web browser.
2 Enter the following at the address prompt:
http://ip_address_of_target:5801
3 Enter your VNC password when prompted to do so. The browser window now
displays the YaST screens as in a normal local installation.
1.5.2 SSH Installation
Using SSH, you can remotely control the installation of your Linux machine using any
SSH client software.
Remote Installation
55
Preparing for SSH Installation
Apart from installing the appropriate software package (OpenSSH for Linux and PuTTY
for Windows), you just need to pass the appropriate boot options to enable SSH for
installation. See Section 1.4.3, “Using Custom Boot Options” (page 51) for details.
OpenSSH is installed by default on any SUSE Linux based operating system.
Connecting to the Installation Program
1 Retrieve the installation target's IP address.
If you have physical access to the target machine, just take the IP address the
installation routine provides at the console after the initial boot. Otherwise take
the IP address that has been assigned to this particular host in the DHCP server
configuration.
2 At a command line enter the following command:
ssh -X [email protected]_address_of_target
Replace ip_address_of_target with the actual IP address of the installation
target.
3 When prompted for a username, enter root.
4 When prompted for password, enter the password that has been set via the SSH
boot option.
After you have successfully authenticated, a command line prompt for the installation target appears.
5 Enter yast to launch the installation program.
A window opens showing the normal YaST screens as described in Chapter Installation with YaST (↑Start-Up).
56
2
Advanced Disk Setup
Sophisticated system configurations require particular disk setups. To get persistent
device naming with SCSI devices, use a specific start-up script. Logical Volume Management (LVM) is a disk partitioning scheme that is designed to be much more flexible
than the physical partitioning used in standard setups. Its snapshot functionality enables
you to create data backups easily. Redundant Array of Independent Disks (RAID) offers
increased data integrity, performance, and fault tolerance.
2.1 Permanent Device Names for
SCSI Devices
When the system is booted, SCSI devices are assigned device filenames in a more or
less dynamic way. This is no problem as long as the number or configuration of the
devices does not change. However, if a new SCSI hard disk is added and the new hard
disk is detected by the kernel before the old hard disk, the old disk is assigned a new
name and the entry in the mount table /etc/fstab no longer matches.
To avoid this problem, the system start-up script boot.scsidev could be used. Enable
this script using /sbin/insserv and set parameters for it in /etc/sysconfig/
scsidev. The script /etc/rc.d/boot.scsidev handles the setup of the SCSI
devices during the boot procedure and enters permanent device names under /dev/
scsi/. These names can then be used in /etc/fstab. In addition, /etc/scsi
.alias can be used to define persistent names for the SCSI configuration. The naming
scheme of the devices in /etc/scsi is explained in man scsidev.
Advanced Disk Setup
57
In the expert mode of the runlevel editor, activate boot.scsidev for level B. The
links needed for generating the names during the boot procedure are then created in
/etc/init.d/boot.d.
TIP: Device Names and udev
For SUSE Linux, although boot.scsidev is still supported, the preferred way
to create persistent device names is to use udev to create device nodes with
persistent names in /dev/by-id/.
2.2 LVM Configuration
This section briefly describes the principles behind LVM and its basic features that
make it useful under many circumstances. In Section 2.2.2, “LVM Configuration with
YaST” (page 60), learn how to set up LVM with YaST.
WARNING
Using LVM might be associated with increased risk, such as data loss. Risks also
include application crashes, power failures, and faulty commands. Save your
data before implementing LVM or reconfiguring volumes. Never work without
a backup.
2.2.1 The Logical Volume Manager
The Logical Volume Manager (LVM) enables flexible distribution of hard disk space
over several file systems. It was developed because sometimes the need to change the
segmentation of hard disk space arises only after the initial partitioning during installation
has already been done. Because it is difficult to modify partitions on a running system,
LVM provides a virtual pool (volume group, VG for short) of memory space from
which logical volumes (LVs) can be created as needed. The operating system accesses
these LVs instead of the physical partitions. Volume groups can span more than only
one disk so that several disks or parts of them may constitute one single VG. This way,
LVM provides a kind of abstraction from the physical disk space that allows its segmentation to be changed in a much easier and safer way than physical repartitioning does.
Background information regarding physical partitioning can be found in Section “Par-
58
tition Types” (Chapter 1, Installation with YaST, ↑Start-Up) and Section “Partitioner”
(Chapter 3, System Configuration with YaST, ↑Start-Up).
Figure 2.1
Physical Partitioning versus LVM
DISK
PART
PART
DISK 1
PART
PART
PART
DISK 2
PART
PART
VG 1
MP
MP
MP
PART
VG 2
LV 1
LV 2
LV 3
LV 4
MP
MP
MP
MP
Figure 2.1, “Physical Partitioning versus LVM” (page 59) compares physical partitioning
(left) with LVM segmentation (right). On the left side, one single disk has been divided
into three physical partitions (PART), each with a mount point (MP) assigned so that
the operating system can access them. On the right side, two disks have been divided
into two and three physical partitions each. Two LVM volume groups (VG 1 and VG 2)
have been defined. VG 1 contains two partitions from DISK 1 and one from DISK 2.
VG 2 contains the remaining two partitions from DISK 2. In LVM, the physical disk
partitions that are incorporated in a volume group are called physical volumes (PVs).
Within the volume groups, four logical volumes (LV 1 through LV 4) have been defined,
which can be used by the operating system via the associated mount points. The border
between different logical volumes need not be aligned with any partition border. See
the border between LV 1 and LV 2 in this example.
LVM features:
• Several hard disks or partitions can be combined in a large logical volume.
• Provided the configuration is suitable, an LV (such as /usr) can be enlarged when
the free space is exhausted.
• Using LVM, even add hard disks or LVs in a running system. However, this requires
hot-swappable hardware that is capable of such actions.
Advanced Disk Setup
59
• It is possible to activate a "striping mode" that distributes the data stream of a logical
volume over several physical volumes. If these physical volumes reside on different
disks, this can improve the reading and writing performance just like RAID 0.
• The snapshot feature enables consistent backups (especially for servers) in the
running system.
With these features, using LVM already makes sense for heavily used home PCs or
small servers. If you have a growing data stock, as in the case of databases, music
archives, or user directories, LVM is just the right thing for you. This would allow file
systems that are larger than the physical hard disk. Another advantage of LVM is that
up to 256 LVs can be added. However, keep in mind that working with LVM is different
from working with conventional partitions. Instructions and further information about
configuring LVM is available in the official LVM HOWTO at http://tldp.org/
HOWTO/LVM-HOWTO/.
Starting from kernel version 2.6, LVM version 2 is available, which is downwardcompatible with the previous LVM and enables the continued management of old volume
groups. When creating new volume groups, decide whether to use the new format or
the downward-compatible version. LVM 2 does not require any kernel patches. It makes
use of the device mapper integrated in kernel 2.6. This kernel only supports LVM version 2. Therefore, when talking about LVM, this section always refers to LVM version 2.
2.2.2 LVM Configuration with YaST
The YaST LVM configuration can be reached from the YaST Expert Partitioner (see
Section “Partitioner” (Chapter 3, System Configuration with YaST, ↑Start-Up)). This
professional partitioning tool enables you to edit and delete existing partitions and
create new ones that should be used with LVM. There, create an LVM partition by first
clicking Create → Do not format then selecting 0x8E Linux LVM as the partition
identifier. After creating all the partitions to use with LVM, click LVM to start the LVM
configuration.
Creating Volume Groups
If no volume group exists on your system yet, you are prompted to add one (see Figure 2.2, “Creating a Volume Group” (page 61)). It is possible to create additional groups
with Add group, but usually one single volume group is sufficient. system is suggested
60
as a name for the volume group in which the SUSE Linux system files are located. The
physical extent size defines the size of a physical block in the volume group. All the
disk space in a volume group is handled in chunks of this size. This value is normally
set to 4 MB and allows for a maximum size of 256 GB for physical and logical volumes.
The physical extent size should only be increased, for example, to 8, 16, or 32 MB, if
you need logical volumes larger than 256 GB.
Figure 2.2
Creating a Volume Group
Configuring Physical Volumes
Once a volume group has been created, the following dialog lists all partitions with either
the “Linux LVM” or “Linux native” type. No swap or DOS partitions are shown. If a
partition is already assigned to a volume group, the name of the volume group is shown
in the list. Unassigned partitions are indicated with “--”.
If there are several volume groups, set the current volume group in the selection box
to the upper left. The buttons in the upper right enable creation of additional volume
groups and deletion of existing volume groups. Only volume groups that do not have
any partitions assigned can be deleted. All partitions that are assigned to a volume group
are also referred to as a physical volumes (PV).
Advanced Disk Setup
61
Figure 2.3
Physical Volume Setup
To add a previously unassigned partition to the selected volume group, first click the
partition then Add Volume. At this point, the name of the volume group is entered next
to the selected partition. Assign all partitions reserved for LVM to a volume group.
Otherwise, the space on the partition remains unused. Before exiting the dialog, every
volume group must be assigned at least one physical volume. After assigning all physical volumes, click Next to proceed to the configuration of logical volumes.
Configuring Logical Volumes
After the volume group has been filled with physical volumes, define the logical volumes
the operating system should use in the next dialog. Set the current volume group in a
selection box to the upper left. Next to it, the free space in the current volume group is
shown. The list below contains all logical volumes in that volume group. All normal
Linux partitions to which a mount point is assigned, all swap partitions, and all already
existing logical volumes are listed here. Add, Edit, and Remove logical volumes as
needed until all space in the volume group has been exhausted. Assign at least one
logical volume to each volume group.
62
Figure 2.4
Logical Volume Management
To create a new logical volume, click Add and fill out the pop-up that opens. As for
partitioning, enter the size, file system, and mount point. Normally, a file system, such
as reiserfs or ext2, is created on a logical volume and is then designated a mount point.
The files stored on this logical volume can be found at this mount point on the installed
system. Additionally it is possible to distribute the data stream in the logical volume
among several physical volumes (striping). If these physical volumes reside on different
hard disks, this generally results in a better reading and writing performance (like
RAID 0). However, a striping LV with n stripes can only be created correctly if the
hard disk space required by the LV can be distributed evenly to n physical volumes.
If, for example, only two physical volumes are available, a logical volume with three
stripes is impossible.
WARNING: Striping
YaST has no chance at this point to verify the correctness of your entries concerning striping. Any mistake made here is apparent only later when the LVM
is implemented on disk.
Advanced Disk Setup
63
Figure 2.5
Creating Logical Volumes
If you have already configured LVM on your system, the existing logical volumes can
be entered now. Before continuing, assign appropriate mount points to these logical
volumes too. With Next, return to the YaST Expert Partitioner and finish your work
there.
Direct LVM Management
If you already have configured LVM and only want to change something, there is an
alternative way to do that. In the YaST Control Center, select System → LVM. Basically
this dialog allows the same actions as described above with the exception of physical
partitioning. It shows the existing physical volumes and logical volumes in two lists
and you can manage your LVM system using the methods already described.
64
2.3 Soft RAID Configuration
The purpose of RAID (redundant array of inexpensive disks) is to combine several hard
disk partitions into one large virtual hard disk to optimize performance, data security,
or both. Using this method, however, one advantage is sacrificed for another. Most
RAID controllers use the SCSI protocol because it can address a larger number of hard
disks in a more effective way than the IDE protocol and is more suitable for parallel
processing of commands. There are some RAID controllers that support IDE or SATA
hard disks. Refer to the Hardware Database at http://cdb.suse.de.
2.3.1 Soft RAID
Like a RAID controller, which can often be quite expensive, soft RAID is also able to
take on these tasks. SUSE Linux offers the option of combining several hard disks into
one soft RAID system with the help of YaST—a very reasonable alternative to hardware
RAID. RAID implies several strategies for combining several hard disks in a RAID
system, each of them having different goals, advantages and characteristics. These
variations are commonly known as RAID levels.
Common RAID levels are:
RAID 0
This level improves the performance of your data access by spreading out blocks
of each file across multiple disk drives. Actually, this is not really a RAID, because
it does not provide data backup, but the name RAID 0 for this type of system has
become the norm. With RAID 0, two or more hard disks are pooled together. The
performance is very good, but the RAID system is destroyed and your data lost if
even one hard disk fails.
RAID 1
This level provides adequate security for your data, because the data is copied to
another hard disk 1:1. This is known as hard disk mirroring. If a disk is destroyed,
a copy of its contents is available on another one. All of them except one could be
damaged without endangering your data. The writing performance suffers a little
in the copying process compared to when using single disk access (ten to twenty
percent slower), but read access is significantly faster in comparison to any one of
the normal physical hard disks, because the data is duplicated so can be parallel
Advanced Disk Setup
65
scanned. Generally it can be said that Level 1 provides nearly twice the read transaction rate of single disks and almost the same write transaction rate as single disks.
RAID 2 and RAID 3
These are not typical RAID implementations. Level 2 stripes data at the bit level
rather than the block level. Level 3 provides byte-level striping with a dedicated
parity disk and cannot service simultaneous multiple requests. Both levels are only
rarely used.
RAID 4
Level 4 provides block-level striping just like Level 0 combined with a dedicated
parity disk. In the case of a data disk failure, the parity data is used to create a replacement disk. However, the parity disk may create a bottleneck for write access.
Nevertheless, Level 4 is sometimes used.
RAID 5
RAID 5 is an optimized compromise between Level 0 and Level 1 in terms of performance and redundancy. The hard disk space equals the number of disks used
minus one. The data is distributed over the hard disks as with RAID 0. Parity blocks,
created on one of the partitions, are there for security reasons. They are linked to
each other with XOR, enabling the contents, via XOR, to be reconstructed by the
corresponding parity block in case of system failure. With RAID 5, no more than
one hard disk can fail at the same time. If one hard disk fails, it must be replaced
as soon as possible to avoid the risk of losing data.
Other RAID Levels
Several other RAID levels have been developed (RAIDn, RAID 10, RAID 0+1,
RAID 30, RAID 50, etc.), some of them being proprietary implementations created
by hardware vendors. These levels are not very widespread, so are not explained
here.
2.3.2 Soft RAID Configuration with YaST
The YaST soft RAID configuration can be reached from the YaST Expert Partitioner,
described in Section “Partitioner” (Chapter 3, System Configuration with YaST, ↑StartUp). This professional partitioning tool enables you to edit and delete existing partitions
and create new ones that should be used with soft RAID. There, create RAID partitions
by first clicking Create → Do not format then selecting 0xFD Linux RAID as the partition
identifier. For RAID 0 and RAID 1, at least two partitions are needed—for RAID 1,
66
usually exactly two and no more. If RAID 5 is used, at least three partitions are required.
It is recommended to take only partitions of the same size. The RAID partitions should
be stored on different hard disks to decrease the risk of losing data if one is defective
(RAID 1 and 5) and to optimize the performance of RAID 0. After creating all the
partitions to use with RAID, click RAID → Create RAID to start the RAID configuration.
In the next dialog, choose between RAID levels 0, 1, and 5 (see Section 2.3.1, “Soft
RAID” (page 65) for details). After Next is clicked, the following dialog lists all partitions with either the “Linux RAID” or “Linux native” type (see Figure 2.6, “RAID
Partitions” (page 67)). No swap or DOS partitions are shown. If a partition is already
assigned to a RAID volume, the name of the RAID device (e.g., /dev/md0) is shown
in the list. Unassigned partitions are indicated with “--”.
Figure 2.6
RAID Partitions
To add a previously unassigned partition to the selected RAID volume, first click the
partition then Add. At this point, the name of the RAID device is entered next to the
selected partition. Assign all partitions reserved for RAID. Otherwise, the space on the
partition remains unused. After assigning all partitions, click Next to proceed to the
settings dialog where you can fine-tune the performance (see Figure 2.7, “File System
Settings” (page 68)).
Advanced Disk Setup
67
Figure 2.7
File System Settings
As with conventional partitioning, set the file system to use as well as encryption and
the mount point for the RAID volume. Checking Persistent Superblock ensures that
the RAID partitions are recognized as such when booting. After completing the configuration with Finish, see the /dev/md0 device and others indicated with RAID in the
expert partitioner.
2.3.3 Troubleshooting
Check the file /proc/mdstats to find out whether a RAID partition has been destroyed. In the event of a system failure, shut down your Linux system and replace the
defective hard disk with a new one partitioned the same way. Then restart your system
and enter the command mdadm /dev/mdX --add /dev/sdX. Replace 'X' with
your particular device identifiers. This integrates the hard disk automatically into the
RAID system and fully reconstructs it.
68
2.3.4 For More Information
Configuration instructions and more details for soft RAID can be found in the HOWTOs
at:
• /usr/share/doc/packages/raidtools/Software-RAID.HOWTO
.html
• http://en.tldp.org/HOWTO/Software-RAID-HOWTO.html
Linux RAID mailing lists are also available, such as http://www.mail-archive
.com/[email protected]
Advanced Disk Setup
69
Part II Internet
The Web Browser Konqueror
3
Konqueror is not only a versatile file manager. It is also a modern Web browser. If you
start the browser with the icon in the panel, Konqueror opens with the Web browser
profile. As a browser, Konqueror offers tabbed browsing, the possibility of saving Web
pages with graphics, Internet keywords, bookmarks, and support for Java and JavaScript.
Figure 3.1
The Browser Window of Konqueror
The Web Browser Konqueror
73
Start Konqueror from the main menu or by entering the command konqueror. To
load a Web page, enter its address in the location bar, for example, http://www
.suse.com. Konqueror now tries to reach the address and display the page. Entering
the protocol at the beginning of the address (http:// in this case) is not strictly required. The program is able to complete the address automatically, but this only works
reliably with Web addresses. For an FTP address, always enter ftp:// at the beginning
of the input field.
3.1 Tabbed Browsing
If you often use more than one Web page at a time, tabbed browsing may make it easier
to switch between them. Load Web sites in separate tabs within one window. The advantage is that you keep more control over your desktop because you only have one
main window. After logout, the KDE session management allows for saving your Web
session in Konqueror. The next time you log in, Konqueror loads the exact URLs visited
last time.
To open a new tab, select Window → New Tab or press Ctrl + Shift + N . To change
the behavior of tabs, go to Settings → Configure Konqueror. In the dialog box that
opens, select Web Behavior → Tabbed Browsing. To open new tabs instead of windows,
enable Open links in new tab instead of in new window. You can also hide the tab bar
with Hide the tab bar when only one tab is open. To see more options, press Advanced
Options.
You can save your tabs with URLs and the position of the window in a profile. This is
a bit different from the session managment mentioned above. With profiles, you have
your saved tabs at hand and without intensive start-up time like with session management.
In Konqueror, go to Settings → Configure View Profiles and give your profile a name.
You can save the window size in the profile, too, with the respective option. Make sure
that Save URLs in profile is selected. Approve with Save. Next time you need your “tab
collection,” go to Settings → Load View Profile and see the name listed in the menu.
After selecting the name, Konqueror restores your tabs.
74
3.2 Saving Web Pages and Graphics
As in other browsers, you can save Web pages. To do this, select Location → Save as
and specify a name for your HTML file. However, images are not saved. To archive
an entire Web page including the images, select Tools → Archive Web Page. Konqueror
suggests a filename that you can usually accept. The filename ends with .war, the
extension for Web archives. To view the saved Web archive later, simply click the respective file and the Web page is displayed in Konqueror along with its images.
3.3 Internet Keywords
Searching the Web using Konqueror is very easy. Konqueror defines over 70 search
filters for you, all with a specific shortcut. To search for a certain topic on the Internet,
enter the shortcut and the keyword separated by a colon. The relevant page containing
the search results is then displayed.
To see the already definied shortcuts, go to Settings → Configure Konqueror. In the
dialog box that appears, select Web Shortcuts. Now you can see the names of the search
providers and the shortcuts. Konqueror definies lots of search filters: the “classical”
search engines, like Google, Yahoo, and Lycos, and a number of filters for less common
purposes, like an acronym database, the Internet movie database, or KDE application
searches.
If you do not find your preferred search engine here, easily define a new one. For example, to search our support database for some interesting articles, normally go to
http://portal.suse.com/, find the search page, and enter your query. This
can be simplified by using shortcuts. In the mentioned dialog box, select New and give
your shortcut a name in Search provider name. Enter your abbreviations in URI shortcuts. There can more than one, separated by commas. The important text field is Search
URI. Pressing Shift + F1 and clicking in the field opens a small help. The search query
is specified as \{@}. The challenge is inserting this at the correct position. In this case,
the settings for the SUSE support database looks like this: Search provider name is
SUSE Support Database, Search URI is (one line) https://portal.suse
.com/PM/page/search.pm?q=\{@}&t=optionSdbKeywords&m=25&l=
en&x=true, and URI shortcuts is sdb_en.
The Web Browser Konqueror
75
After approving with Ok two times, enter your query in Konqueror's location bar, for
example, sdb_en:kernel. The result is displayed in the current window.
3.4 Bookmarks
Instead of remembering and reentering addresses for sites visited often, you can bookmark these URLs using the Bookmark menu. Apart from Web page addresses, you can
also bookmark any directories of your local disk in this way.
To create a new bookmark in Konqueror, click Bookmarks → Add Bookmark. Any
bookmarks added previously are included as items in the menu. It is a good idea to arrange the bookmark collection by subjects in a hierarchical structure, so that you do
not lose track of the different items. Create a new subgroup for your bookmarks with
New Bookmark Folder. Selecting Bookmarks → Edit Bookmarks opens the bookmark
editor. Use this program to organize, rearrange, add, and delete bookmarks.
If you are using Netscape, Mozilla, or Firefox as additional browsers, it is not necessary
to recreate your bookmarks. File → Import → Import Netscape Bookmarks in the
bookmark editor enables you to integrate your Netscape and Mozilla bookmarks into
your most current collection. The reverse is also possible via Export as Netscape
Bookmarks.
Change your bookmarks by right-clicking the entry. A pop-up menu appears in which
to select the desired action (cut, copy, delete, etc.). When you are satisfied with the result,
save the bookmarks with File → Save. If you only want to change the name or link,
just right-click the entry in the bookmark toolbar and select Properties. Change the
name and location and confirm with Update.
To save your bookmark list and have instant access to it, make your bookmarks visible
in Konqueror. Select Settings → Toolbars → Bookmark Toolbar (Konqueror). A
bookmark panel is automatically displayed in the current Konqueror window.
3.5 Java and JavaScript
Do not confuse these two languages. Java is an object-oriented, platform-independent
programming language from Sun Microsystems. It is frequently used for small programs
(applets), which are executed over the Internet for things like online banking, chatting,
76
and shopping. JavaScript is an interpreted scripting language mainly used for the dynamic structuring of Web pages, for example, for menus and other effects.
Konqueror allows you to enable or disable these two languages. This can even be done
in a domain-specific way, which means that you can permit access for some hosts and
block access for others. Java and JavaScript are often disabled for security reasons.
Unfortunately, some Web pages require JavaScript for correct display.
3.6 For More Information
For any questions or problems that arise when working with Konqueror, refer to the
application's handbook, which is available from the Help menu. Konqueror also has a
Web page, located at http://www.konqueror.org.
The Web Browser Konqueror
77
4
Firefox
Included with your SUSE Linux is the Mozilla Firefox Web browser. With features
like tabs, pop-up window blocking, and download and image management, Firefox
combines the latest Web technologies. View more than one Web page in a single window. Suppress annoying advertisements and disable images that only slow you down.
Its easy access to different search engines helps you find the information you need.
Start the program from the main menu or by entering the command firefox. The
main program features are described in the following sections.
4.1 Navigating Web Sites
Firefox has much the same look and feel as other browsers. It is shown in Figure 4.1,
“The Browser Window of Firefox” (page 80). The navigation toolbar includes Forward
and Back and a location bar for a Web address. Bookmarks are also available for quick
access. For more information about the various Firefox features, use the Help menu.
Firefox
79
Figure 4.1
The Browser Window of Firefox
4.1.1 Tabbed Browsing
If you often use more than one Web page at a time, tabbed browsing may make it easier
to switch between them. Load Web sites in separate tabs within one window.
To open a new tab, select File → New Tab. This opens an empty tab in the Firefox
window. Alternatively, right-click a link and select Open link in new tab. Right-click
the tab itself to access more tab options. You can create a new tab, reload one or all
existing tabs, or close them.
80
4.1.2 Using the Sidebar
Use the left side of your browser window for viewing bookmarks or the browsing history. Extensions may add new ways to use the sidebar as well. To display the Sidebar,
select View → Sidebar and select the desired contents.
4.2 Finding Information
There are two ways to find information in Firefox: the search bar and the find bar. The
search bar looks for pages while the find bar looks for things on the current page.
4.2.1 Using the Search Bar
Firefox has a search bar that can access different engines, like Google, Yahoo, or
Amazon. For example, if you want to find information about SUSE using the current
engine, click in the search bar, type SUSE, and hit Enter . The results appear in your
window. To choose your search engine, click the icon in the search bar. A menu opens
with a list of available search engines.
4.2.2 Using the Find Bar
To search inside a Web page, click Edit → Find in This Page or press Ctrl + F and the
find bar opens. Usually, it is displayed at the bottom of a window. Type your query in
the input field. Firefox highlights all occurrences of this phrase. With Highlight, enable
and disable the highlighting.
4.3 Managing Bookmarks
Bookmarks offer a convenient way of saving links to your favorite Web sites. To add
the current Web site to your list of bookmarks, click Bookmarks → Bookmark This
Page. If your browser currently displays multiple Web sites on tabs, only the URL on
the currently selected tab is added to your list of bookmarks.
Firefox
81
When adding a bookmark, you can specify an alternative name for the bookmark and
select a folder where Firefox should store it. To remove a Web site from the bookmarks
list, click Bookmarks, right-click the bookmark in the list, then click Delete.
4.3.1 Using the Bookmark Manager
The bookmark manager can be used to manage the properties (name and address location) for each bookmark and organize the bookmarks into folders and sections. It resembles Figure 4.2, “Using the Firefox Bookmark Manager” (page 82).
Figure 4.2
Using the Firefox Bookmark Manager
To open the bookmark manager, click Bookmark → Manage Bookmarks. A window
opens and displays your bookmarks. With New Folder, create a new folder with a name
and a description. If you need a new bookmark, click New Bookmark. This let you insert
the name, location, keywords, and also a description. The keyword is a shortcut to your
bookmark. If you need your newly created bookmark in the sidebar, check Load this
bookmark in the sidebar.
82
4.3.2 Migrating Bookmarks
If you used a different browser in the past, you probably want to use your preferences
and bookmarks in Firefox, too. At the moment, you can import from Netscape 4.x, 6,
7, Mozilla 1.x, and Opera.
To import your settings, click File → Import. Select the browser from which to import
settings. After you click Next, your settings are imported. Find your imported bookmarks
in a newly created folder, beginning with From.
4.3.3 Live Bookmarks
Live Bookmarks displays headlines in your bookmarks menu and keep you up to date
with the latest news. This enables you to save time with one glance from your favorite
sites.
Many sites and blogs support this format. A Web site indicates this by showing an orange
rectangle with RSS inside on the bottom right corner. Click it and choose Subscribe to
NAME OF THE FEED. A dialog box opens where you can select the name and location
of your Live Bookmark. Confirm with Add.
Some sites do not tell Firefox that they support a news feed, although they actually do.
To manually add a Live Bookmark, you need the URL of the feed. Do the following:
Procedure 4.1
Adding a Live Bookmark Manually
1 Open the bookmark manager with Bookmarks → Manage Bookmarks. A new
window opens.
2 Select File → New Live Bookmark. A dialog box opens.
3 Insert a name for the Live Bookmark and add your URL, for example, http://
www.novell.com/newsfeeds/rss/coolsolutions.xml. Firefox
updates your Live Bookmarks.
4 Close your bookmark manager.
Firefox
83
4.4 Using the Download Manager
With the help of the download manager, keep track of your current and past downloads.
To open the download manager, click Tools → Downloads. Firefox opens a window
with your downloads. While downloading a file, see a progress bar and the current file.
Pause the download and resume it later, if necessary. To open a downloaded file, click
Open. With Remove, erase it from the medium. If you need information about the file,
right-click the filename and choose Properties.
If you need further control of the Download Manager, open the configuration window
from Edit → Preferences and go to the Downloads tab. Here, determine the download
folder, how the manager behaves, and some configuration of file types.
4.5 Customizing Firefox
With the ability to install extensions, change themes, and add smart keywords for your
online searches, Firefox can be customized extensively.
4.5.1 Extensions
Mozilla Firefox is a multifunctional application, which means that you can download
and install add-ons, known as extensions. For example, add a new download manager
and mouse gestures. This has the advantage that Firefox itself stays small and unbloated.
To add an extension, click Tools → Extensions. In the bottom-right corner, click Get
More Extensions to open the Mozilla extensions update Web page where you can choose
from a variety of available extensions. Click the extension to install then click the install
link to download and install it. When you restart Firefox, the new extension is functional.
You can also look at the various extensions at http://update.mozilla.org/
.
84
Figure 4.3
Installing Firefox Extensions
4.5.2 Changing Themes
If you do not like the standard look and feel of Firefox, install a new theme. Themes
do not change the functionality, only the appearance of the browser. When installing a
theme, Firefox asks for confirmation first. Allow the installation or cancel it. After a
successful installation, you can enable the new theme.
1 Click Tools → Theme.
2 A new dialog appears. Click Get More Themes. If you already installed a theme,
find it in the list, as in Figure 4.4, “Installing Firefox Themes” (page 86).
Firefox
85
Figure 4.4
Installing Firefox Themes
3 A new window appears with the Web site https://update.mozilla.org.
4 Choose a theme and click Install Now.
5 Confirm the download and installation.
6 After downloading the theme, a dialog appears and informs you about your list
of themes. Activate the new theme with Use Theme.
7 Close the window and restart Firefox.
If a theme is installed, you can always switch to a different theme without restarting
by clicking Tools → Themes then Use Theme. If you do not use a theme anymore, you
can delete it in the same dialog with Uninstall.
4.5.3 Adding Smart Keywords to Your
Online Searches
Searching the Internet is one of the main tasks a browser can perform for you. Firefox
lets you define your own smart keywords: abbreviations to use as a “command” for
searching the Web. For example, if you use Wikipedia often, use a smart keyword to
simplify this task:
86
1 Go to http://en.wikipedia.org.
2 After Firefox displays the Web page, see the search text field. Right-click it then
choose Add a Keyword for this Search from the menu that opens.
3 The Add Bookmark dialog appears. In Name, name this Web page, for example,
Wikipedia (en).
4 For Keyword, enter your abbreviation of this Web page, for example, wiki.
5 With Create in, choose the location of the entry in your bookmarks section. You
can put it into Quick Searches, but any other level is also appropriate.
6 Finalize with Add.
You have successfully generated a new keyword. Whenever you need to look into
Wikipedia, you do not have to use the entire URL. Just type wiki Linux to view an
entry about Linux.
4.6 Printing from Firefox
Configure the way Firefox prints the content it displays using the Page Setup dialog.
Click File → Page Setup then go to the Format & Options tab to select the orientation
of your print jobs. You can scale or make it adjust automatically. To print a background,
select Print Background (colors & images). Click the Margins & Header/Footer tab
to adjust margins and select what to include in the headers and footers.
After you configured your settings, print a Web page with File → Print. Select the
printer or a file in which to save the output. With Properties, set the paper size, specify
the print command, choose grayscale or color, and determine the margins. When satisfied
with your settings, approve with Print.
4.7 For More Information
Get more information about Firefox from the official home page at http://www
.mozilla.org/products/firefox/. Refer to the integrated help to find out
more about certain options or features.
Firefox
87
Linphone—VoIP for the Linux
Desktop
5
Linphone is a small Web phone application for your Linux desktop. It allows you to
make two-party calls over the Internet. There is no need for special hardware items: a
standard workstation with a properly configured sound card, microphone, and speakers
or headphones is all you need to get started with Linphone.
5.1 Configuring Linphone
Before you start using Linphone there are some basic decisions to make and some
configuration tasks to complete. First, determine and configure the run mode of Linphone, determine the connection type to use, then start the Linphone configuration (Go
→ Preferences) to make the necessary adjustments.
5.1.1 Determining the Run Mode of
Linphone
Linphone can be run in two different different modes, depending on the type of desktop
you run and on its configuration.
Normal Application
After the Linphone software has been installed, it can be started via the GNOME
and KDE application menus or via the command line. When Linphone is not running,
incoming calls cannot be received.
Linphone—VoIP for the Linux Desktop
89
GNOME Panel Applet
Linphone can be added to the GNOME panel. Right-click an empty area in the
panel, select Add to Panel, and select Linphone. Linphone is then permanently added
to the panel and automatically started on login. As long as you do not receive any
incoming calls, it runs in the background. As soon as you get an incoming call, the
main window opens and you can receive the call. To open the main window to call
someone, just click the applet icon.
5.1.2 Determining the Connection Type
There are several different ways to make a call in Linphone. How you make a call and
how you reach the other party is determined by the way you are connected to the network
or the Internet.
Linphone uses the session initiation protocol (SIP) to establish a connection with a remote host. In SIP, each party is identified by a SIP URL:
sip:[email protected]
username is your login on your Linux machine and hostname the name of the
computer you are using. If you use a SIP provider, the URL would look like the following example:
sip:[email protected]
username is the username chosen when registering at a SIP server. sipserver is
the address of the SIP server or your SIP provider. For details on the registration procedure, refer to Section 5.1.5, “Configuring the SIP Options” (page 92) and check the
provider's registration documentation. For a list of providers suitable for your purpose,
check the Web pages mentioned in Section 5.8, “For More Information” (page 99).
The URL to use is determined by the type of connection you choose. If you chose to
call another party directly without any further routing by a SIP provider, you would
enter a URL of the first type. If you chose to call another party via a SIP server, you
would enter a URL of the second type.
Calling in the Same Network
If you intend to call a friend or coworker belonging to the same network, you just need
the correct username and hostname to create a valid SIP URL. The same applies if this
90
person wants to call you. As long as there is no firewall between you and the other
party, no further configuration is required.
Calling across Networks or the Internet (Static IP
Setup)
If you are connected to the Internet using a static IP address, anyone who wants to call
you just needs your username and the hostname or IP address of your workstation to
create a valid SIP URL, as described in Section “Calling in the Same Network”
(page 90). If you or the calling party are located behind a firewall that filters incoming
and outgoing traffic, open the SIP port (5060) and the RTP port (7078) on the firewall
machine to enable Linphone traffic across the firewall.
Calling across Networks or the Internet (Dynamic IP
Setup)
If your IP setup is not static—if you dynamically get a new IP address every time you
connect to the Internet—it is impossible for any caller to create a valid SIP URL based
on your username and an IP address. In these cases, either use the services offered by
a SIP provider or use a DynDNS setup to make sure that an external caller gets connected
to the right host machine. More information about DynDNS can be found at http://
en.wikipedia.org/wiki/Dynamic_DNS.
Calling across Networks and Firewalls
Machines hidden behind a firewall do not reveal their IP address over the Internet. Thus,
they cannot be reached directly from anyone trying to call a user working at such a
machine. Linphone supports calling across network borders and firewalls by using a
SIP proxy or relaying the calls to a SIP provider. Refer to Section 5.1.5, “Configuring
the SIP Options” (page 92) for a detailed description of the necessary adjustments for
using an external SIP server.
5.1.3 Configuring the Network Parameters
Most of the settings contained in the Network tab do not need any further adjustments.
You should be able to make your first call without changing them.
Linphone—VoIP for the Linux Desktop
91
NAT Traversal Options
Enable this option only if you find yourself in a private network behind a firewall
and if you do not use a SIP provider to route your calls. Select the check box and
enter the IP address of the firewall machine in dot notation, for example,
192.168.34.166.
RTP Properties
Linphone uses the real-time transport protocol (RTP) to transmit the audio data of
your calls. The port for RTP is set to 7078 and should not be modified, unless you
have another application using this port. The jitter compensation parameter is used
to control the number of audio packages Linphone buffers before actually playing
them. By increasing this parameter, you improve the quality of transmission. The
more packages buffered, the greater a chance for “late comers” to be played back.
On the other hand increasing the number of buffered packages also increases the
latency—you hear the voice of your counterpart with a certain delay. When changing
this parameter, carefully balance these two factors.
Other
If you use a combination of VoIP and landline telephony, you might want to use
the dual tone multiplexed frequency (DTMF) technology to trigger certain actions,
like a remote check of your voice mail just by punching certain keys. Linphone
supports two protocols for DTMF transmission, SIP INFO and RTP rfc2833. If you
need DTMF functionality in Linphone, choose a SIP provider that supports one of
these protocols. For a comprehensive list of VoIP providers, refer to Section 5.8,
“For More Information” (page 99).
5.1.4 Configuring the Sound Device
Once your sound card has been properly detected by Linux, Linphone automatically
uses the detected device as the default sound device. Leave the value of Use sound device
as it is. Use Recording source to determine which recording source should be used. In
most cases, this would be a microphone (micro). To select a custom ring sound, use
Browse to choose one and test your choice using Listen. Click Apply to accept your
changes.
5.1.5 Configuring the SIP Options
The SIP dialog contains all SIP configuration settings.
92
SIP Port
Determine on which port the SIP user agent should run. The default port for SIP is
5060. Leave the default setting unchanged unless you know of any other application
or protocol that needs this port.
Identity
Anyone who wants to call you directly without using a SIP proxy or a SIP provider
needs to know your valid SIP address. Linphone creates a valid SIP address for you.
Remote Services
This list holds one or more SIP service providers where you have created a user
account. Server information can be added, modified, or deleted at any time. See
Adding a SIP Proxy and Registering at a Remote SIP Server (page 93) to learn
about the registration procedure.
Authentication Information
To register at a remote SIP server, provide certain authentication data, such as a
password and username. Linphone stores this data once provided. To discard this
data for security reasons, click Clear all stored authentification data.
The Remote services list can be filled with several addresses of remote SIP proxies or
service providers.
Procedure 5.1
Adding a SIP Proxy and Registering at a Remote SIP Server
1 Choose a suitable SIP provider and create a user account there.
2 Start Linphone.
3 Go to Go → Preferences → SIP.
4 Click Add proxy/registrar to open a registration form.
5 Fill in the appropriate values for Registration Period, SIP Identity, SIP Proxy
and Route. If working from behind a firewall, always select Send registration
and enter an appropriate value for Registration Period. This resends the original
registration data after a given time to keep the firewall open at the ports needed
by Linphone. Otherwise, these ports would automatically be closed if the firewall
did not receive any more packages of this type. Resending the registration data
is also needed to keep the SIP server informed about the current status of the
Linphone—VoIP for the Linux Desktop
93
connection and the location of the caller. For SIP identity, enter the SIP URL
that should be used for local calls. To use this server also as a SIP proxy, enter
the same data for SIP Proxy. Finally, add an optional route, if needed, and leave
the dialog with OK.
5.1.6 Configuring the Audio Codecs
Linphone supports a several codecs for the transmission of voice data. Set your connection type and choose your preferred codecs from the list window. Codecs not suitable
for your current connection type are red and cannot be selected.
5.2 Testing Linphone
Check your Linphone configuration using sipomatic, a small test program that can
answer calls made from Linphone.
Procedure 5.2
Testing a Linphone Setup
1 Open a terminal.
2 Enter sipomatic at the command line prompt.
3 Start Linphone.
4 Enter sip:[email protected]:5064 as SIP address and click Call or Answer.
5 If Linphone is configured correctly, you will hear a phone ringing and, after a
short while, you will hear a short announcement.
If you successfully completed this procedure, you can be sure that your audio setup and
the network setup are working. If this test fails, check whether your sound device is
correctly configured and whether the playback level is set to a reasonable value. If you
still fail to hear anything, check the network setup including the port numbers for SIP
and RTP. If any other application or protocol uses the defaults ports for these as proposed
by Linphone, consider changing ports and retry.
94
5.3 Making a Call
Once Linphone is configured appropriately, making a call is straightforward. Depending
on the type of call (see Section 5.1.2, “Determining the Connection Type” (page 90)
for reference), the calling procedures differ slightly.
1 Start Linphone using the menu or a command line.
2 Enter the SIP address of the other party at the SIP address prompt. The address
should look like sip:[email protected] or [email protected]
for direct local calls or like [email protected] or [email protected]
for proxied calls or calls using the service of a SIP provider.
3 If using a SIP service provider or a proxy, select the appropriate proxy or provider
from Proxy to use and provide the authentication data requested by this proxy.
4 Click Call or Answer and wait for the other party to pick up the phone.
5 Once you are done or wish to end the call, click Release or Refuse and leave
Linphone.
If you need to tweak the sound parameters during a call, click Show more to show four
tabs holding more options. The first one holds the Sound options for Playback level
and Recording level. Use the sliders to adjust both volumes to fit your needs.
The Presence tab lets you set your online status. This information can be relayed to
anyone who tries to contact you. If you are permanently away and wish to inform the
calling party of this fact, just check Away. If you are just busy, but want the calling
party to retry, check Busy, I'll be back in ... min and specify how long you will not be
reachable. Once you are reachable again, set the status back to the default (Reachable).
Whether another party can check your online status is determined by the Subscribe
Policy set in the address book, as described in Section 5.5, “Using the Address Book”
(page 96). If any party listed in your address book published their online status, you
can monitor it using the My online friends tab.
The DTMF tab can be used to enter DTMF codes for checking voice mail. To check
your voice mail, enter the appropriate SIP address and use the keypad in the DTMF tab
to enter the voice mail code. Finally, click Call or Answer as if you were making an
ordinary call.
Linphone—VoIP for the Linux Desktop
95
5.4 Answering a Call
Depending on the run mode selected for Linphone, there are several ways you would
notice an incoming call:
Normal Application
Incoming calls can only be received and answered if Linphone is already running.
You then hear the ring sound on your headset or your speakers. If Linphone is not
running, the call cannot be received.
GNOME Panel Applet
Normally, the Linphone panel applet would run silently without giving any notice
of its existence. This changes as soon as a call comes in: the main window of Linphone opens and you hear a ring sound on your headset or speakers.
Once you have noticed an incoming call, just click Call or Answer to pick up the phone
and start talking. If you do not want to accept this call, click Release of Refuse.
5.5 Using the Address Book
Linphone offers to manage your SIP contacts. Start the address book with Go → Address
book. An empty list window opens. Click Add to add a contact.
The following entries need to be made for a valid contact:
Name
Enter the name of your contact. This may be a full name, but you can also use a
nickname here. Choose something you easily remember this person as. If you choose
to see this person's online status, this name is shown in the My online friends tab of
the main window.
SIP Address
Enter a valid SIP address for your contact.
Proxy to Use
If needed, enter the proxy to use for this particular connection. In most cases, this
would just be the SIP address of the SIP server you use.
96
Subscribe Policy
Your subscribe policy determines whether your presence or absence can be tracked
by others.
To call any contact from the address book, select this contact with the mouse, click
Select to make the address appear in the address field of the main window, and start
the call with Call or Answer as usual.
5.6 Troubleshooting
I try to call someone, but fail to establish a connection.
There are several reasons why a call could fail:
Your connection to the Internet is broken.
Because Liphone uses the Internet to relay your calls, make sure that your
computer is properly connected to and configured for the Internet. This can
easily be tested by trying to view a Web page using your browser. If the Internet
connection works, the other party might not be reachable.
The person you are calling is not reachable.
If the other party refused your call, you would not be connected. If Linphone is
not running on the other party's machine while you are calling, you will not be
connected. If the other party's Internet connection is broken, you cannot make
the connection.
My call seems to connect, but I cannot hear anything.
First, make sure that your sound device is properly configured. Do this by launching
any other application using sound output, such as a media player. Make sure that
Linphone has sufficient permissions to open this device. Close all other programs
using the sound device to avoid resource conflicts.
If the above checks were successful, but you still fail to hear anything, raise the
recording and playback levels under the Sound tab.
The voice output on both ends sounds strangely clipped.
Try to adjust the jitter buffer using RTP properties in Preferences → Network to
compensate for delayed voice packages. When doing this, be aware that it increases
the latency.
Linphone—VoIP for the Linux Desktop
97
DTMF does not work.
You tried to check your voice mail using the DTMF pad, but the connection could
not be established. There are three different protocols used for the transmission of
DTMF data, but only two of these are supported by Linphone (SIP INFO and RTP
rfc2833). Check with your provider whether it supports one of these. The default
protocol used by Linphone is rfc2833, but if that fails you can set the protocol to
SIP INFO in Preferences → Network → Other. If it does not work with either of
them, DTMF transmission cannot be done using Linphone.
5.7 Glossary
Find some brief explanation of the most important technical terms and protocols mentioned in this document:
VoIP
VoIP stands for voice over Internet protocol. This technology allows the transmission
of ordinary telephone calls over the Internet using packet-linked routes. The voice
information is sent in discrete packets like any other data transmitted over the Internet
via IP.
SIP
SIP stands for session initiation protocol. This protocol is used to establish media
sessions over networks. In a Linphone context, SIP is the magic that triggers the
ring at your counterpart's machine, starts the call, and also terminates it as soon as
one of the partners decides to hang up. The actual transmission of voice data is
handled by RTP.
RTP
RTP stands for real-time transport protocol. It allows the transport of media streams
over networks and works over UDP. The data is transmitted by means of discrete
packets that are numbered and carry a time stamp to allow correct sequencing and
the detection of lost packages.
DTMF
A DTMF encoder, like a regular telephone, uses pairs of tones to represent the various keys. Each key is associated with a unique combination of one high and one
low tone. A decoder then translates these touch-tone combinations back into numbers.
Linphone supports DTMF signalling to trigger remote actions, such as checking
voice mail.
98
codec
Codecs are algorithms specially designed to compress audio and video data.
jitter
Jitter is the variance of latency (delay) in a connection. Audio devices or connectionoriented systems, like ISDN or PSTN, need a continuous stream of data. To compensate for this, VoIP terminals and gateways implement a jitter buffer that collect
the packets before relaying them onto their audio devices or connection-oriented
lines (like ISDN). Increasing the size of the jitter buffer decreases the likelihood of
data being missed, but the latency of the connection is increased.
5.8 For More Information
For general information about VoIP, check the VoIP Wiki at http://voip-info
.org/tiki-index.php. For a comprehensive list of providers offering VoIP services in your home country, refer to http://voip-info.org/wiki-VOIP
+Service+Providers+Residential.
Linphone—VoIP for the Linux Desktop
99
6
Encryption with KGpg
KGpg is an important component of the encryption infrastructure on your system. With
the help of this program, generate and manage all needed keys, use its editor function
for the quick creation and encryption of files, or use the applet in your panel to encrypt
or decrypt by dragging and dropping. Other programs, such as your mail program
(Kontact or Evolution), access the key data to process signed or encrypted contents.
This chapter covers the basic functions needed for daily work with encrypted files.
6.1 Generating a New Key Pair
To be able to exchange encrypted messages with other users, first generate your own
key pair. One part of it—the public key—is distributed to your communication partners,
who can use it to encrypt the files or e-mail messages they send. The other part of the
key pair—the private key—is used to decrypt the encrypted contents.
IMPORTANT: Private Key versus Public Key
The public key is intended for the public and should be distributed to all your
communication partners. However, only you should have access to the private
key. Do not grant other users access to this data.
Start KGpg from the main menu by selecting Utilities → KGpg or enter kgpg on the
command line. When you start the program for the first time, an assistant appears to
guide you through the configuration. Follow the instructions up to the point where you
are prompted to create a key. Enter a name, an e-mail address, and, optionally, a comment. If you do not like the default settings provided, also set the expiration time for
Encryption with KGpg
101
the key, the key size, and the encryption algorithm used. See Figure 6.1, “KGpg: Creating a Key” (page 102).
Figure 6.1
KGpg: Creating a Key
Confirm your settings with OK. The next dialog prompts you to enter a password twice.
The program then generates the key pair and displays a summary. It is a good idea to
save or print a revocation certificate right away. Such a certificate will be needed if you
forget the password for your private key so need to revoke it. After you confirm with
OK, KGpg displays its main window. See Figure 6.2, “The Key Manager” (page 103).
102
Figure 6.2
The Key Manager
6.2 Exporting the Public Key
After generating your key pair, make the public key available to other users. This enables
them to use it to encrypt or sign the messages or files they send you. To make the public
key available for others, select Keys → Export Public Key(s). The dialog that opens
offers four options:
Email
Your public key is sent to a recipient of your choice by e-mail. If you activate this
option and confirm with OK, the dialog for creating a new e-mail message with
KMail appears. Enter the recipient and click Send. The recipient receives your key
and can then send you encrypted contents.
Clipboard
You can place your public key here before continuing to process it.
Default Key Server
To make your public key available to a wide audience, export it to one of the key
servers on the Internet. For more information, refer to Section 6.4, “The Key Server
Dialog” (page 105).
File
If you prefer to distribute your key as a file on a data medium instead of sending it
by e-mail, click this option, confirm or change the file path and name, and click
OK.
Encryption with KGpg
103
6.3 Importing Keys
If you receive a key in a file (for example, as an e-mail attachment), integrate it in your
key ring with Import Key and use it for encrypted communication with the sender. The
procedure is similar to the procedure for exporting keys already described.
6.3.1 Signing Keys
Keys can be signed like every other file to guarantee their authenticity and integrity. If
you are absolutely sure an imported key belongs to the individual specified as the
owner, express your trust in the authenticity of the key with your signature.
IMPORTANT: Establishing a Web of Trust
Encrypted communication is only secure to the extent that you can positively
associate public keys in circulation with the specified user. By cross-checking
and signing these keys, you contribute to the establishment of a web of trust.
Select the key to sign in the key list. Select Keys → Sign Keys. In the following dialog,
designate the private key to use for the signature. An alert reminds you to check the
authenticity of this key before signing it. If you have performed this check, click Continue and enter the password for the selected private key in the next step. Other users
can now check the signature by means of your public key.
6.3.2 Trusting Keys
Normally, you are asked by the corresponding program whether you trust the key
(whether you assume it is really used by its authorized owner). This happens each time
a message needs to be decrypted or a signature must be checked. To avoid this, edit the
trust level of the newly imported key.
Right-click the newly imported key to access a small context menu for key management.
Select Edit Key in Terminal from it. KGpg opens a text console in which to set the trust
level with a few commands.
At the prompt of the text console (Command >), enter trust. On a scale between 1
(unsure) and 5 (complete trust) make an estimate of how much you trust that the signers
104
of the imported key have checked the true identity of the key owner. Enter the selected
value at the prompt (Your decision?). If you are really sure about the signers'
trustworthiness, enter 5. Answer the following question by entering y. Finally, enter
quit to exit the console and return to the list of keys. The key now has the trust level
Ultimate.
The trust level of the keys in your key ring is indicated by a colored bar next to the key
name. The lower the trust level is, the less you trust the signer of the key to have checked
the true identity of the keys signed. You may be entirely sure about the signer's identity,
but he may still be lazy in regard to checking other people's identities before signing
their keys. Therefore, you could still trust him and his own key, but assign lower trust
levels to the keys of others that have been signed by him. The trust level's purpose is
solely one of a reminder. It does not trigger any automatic actions by KGpg.
6.4 The Key Server Dialog
Several Internet-based key servers offer the public keys of many users. To engage in
encrypted communication with a large number of users, use these servers to distribute
your public key. For this purpose, export your public key to one of these servers. Similarly, KGpg enables you to search one of these servers for the keys of certain people
and import their public keys from the server. Open the key server dialog with File →
Key Server Dialog.
6.4.1 Importing a Key from a Key Server
By means of the Import tab in the key server dialog, import public keys from one of
the Internet-based key servers. Use the drop-down menu to select one of the preconfigured key servers and enter a search string (e-mail address of the communication partner)
or the ID of the key to find. When you click Search, your system connects to the Internet
and searches the specified key server for a key that matches your specifications. Refer
to Figure 6.3, “Search Screen for Importing a Key” (page 106).
Encryption with KGpg
105
Figure 6.3
Search Screen for Importing a Key
If your search on the key server is successful, a list of all retrieved server entries is
displayed in a new window. Select the key to include in your key ring and click Import.
See Figure 6.4, “Hits and Import” (page 106). Confirm the following message with OK
then exit the key server dialog with Close. The imported key then appears in the main
overview of the key manager and is ready for use.
Figure 6.4
106
Hits and Import
6.4.2 Exporting Your Keys to a Key Server
To export your key to one of the freely accessible key servers on the Internet, select
the Export tab in the key server dialog. Designate the target server and the key to export
by means of two drop-down menus. Then start the export with Export.
Figure 6.5
Exporting a Key to a Key Server
6.5 Text and File Encryption
KGpg also offers the possibility to encrypt text or clipboard contents. Click the padlock
icon and find the options Encrypt clipboard and Decrypt clipboard as well as the option
for opening the integrated editor.
6.5.1 Encrypting and Decrypting the
Clipboard
Files copied to the clipboard can easily be encrypted with a few clicks. Open the function
overview by clicking the KGpg icon. Select Encrypt Clipboard and designate the key
to use. A status message about the encryption procedure is displayed on the desktop.
The encrypted contents can now be processed from the clipboard as needed. The decryption of clipboard contents is just as easy. Simply open the menu on the panel, select
Decrypt Clipboard, and enter the password associated with your private key. The decrypted version is now available for processing in the clipboard and in the KGpg editor.
Encryption with KGpg
107
6.5.2 Encrypting and Decrypting by
Dragging and Dropping
To encrypt or decrypt files, click the icons on the desktop or in the file manager, drag
them to the padlock in the panel, and drop them there. If the file is not encrypted, KGpg
asks for the key to use. As soon as you select a key, the file is encrypted without any
further messages. In the file manager, encrypted files are designated with the suffix
.asc and the padlock icon. These files can be decrypted by clicking the file icon,
dragging it to the KGpg symbol in the panel, and dropping it there. Then select whether
the file should be decrypted and saved or displayed in the editor.
6.5.3 The KGpg Editor
Instead of creating contents for encryption in an external editor then encrypting the file
with one of the methods described above, you can use the integrated editor of KGpg
to create the file. Open the editor (Open Editor from the context menu), enter the desired
text, and click Encrypt. Then select the key to use and complete the encryption procedure.
To decrypt files, use Decrypt and enter the password associated with the key.
Generating and checking signatures is just as easy as encrypting directly from the editor.
Go to Signature → Generate Signature and select the file to sign from the file dialog.
Then designate the private key to use and enter the associated password. KGpg informs
about the successful generation of the signature. Files can also be signed from the editor
by simply clicking Sign/Verify. To check a signed file, go to Signature → Verify Signature and select the file to check in the following dialog. After you confirm the selection,
KGpg checks the signature and reports the result of the operation. Another possibility
is to load the signed file into the editor and click Sign/Verify.
6.6 For More Information
For theoretical background information about the encryption method, refer to the brief
and clear introduction on the GnuPG project pages at http://www.gnupg.org/
documentation/howtos.html.en. This document also provides a list of further
information sources.
108
Part III Multimedia
7
Sound in Linux
Linux includes a wide range of sound and multimedia applications. Some of these applications are part of one of the main desktop environments. With the applications described here, control the volume and balance of playback, play CDs and music files,
and record and compress your own audio data.
7.1 Mixers
Mixers provide a convenient means of controlling the volume and balance of the sound
output and input of computers. The main difference between the various mixers is the
outer appearance of the user interface. However, there are a number of mixers that are
designed for specific hardware. One example is envy24control, a mixer for the Envy 24
sound chip. Another one is hdspmixer, which is for RME Hammerfall cards. From the
mixers available, select the one that best suits your needs.
TIP: Test your Mixer
Generally, it is advisable to open a mixer application before opening other
sound applications. Use the mixer to test and adjust the control settings for
the input and output of the sound card.
7.1.1 The KDE Mixer Applet
KMix is the KDE mixer application. It is integrated into the KDE panel as a small
panel applet located in the system tray. Click the panel icon to control the volume of
Sound in Linux
111
your speakers with a control slider. If you right-click the icon, the context menu of
KMix appears. Select Mute to switch off the sound output. The panel icon then changes
its appearance. Clicking Mute again unmutes the volume. To fine-tune your sound settings, select Show Mixer Window and configure Output, Input, and Switches. Each of
the devices featured there has its own context menu that is opened by a right-clicking
the device icon. You can mute or hide each one of them separately.
Figure 7.1
The Mixer KMix
7.1.2 The GNOME Mixer Applet
GMix, the volume control applet for the GNOME desktop, is integrated into the GNOME
panel. Click the panel icon to control the volume of your speakers with a simple control
slider. To switch off the sound output, right-click the icon and select Mute. The volume
control icon then changes its appearance. To unmute the sound output, right-click the
icon again and select Mute from the menu. Select Open Volume Control to access the
more advanced mixer features, shown in Figure 7.2, “The GNOME Mixer Applet”
(page 113). Each sound device has its own mixer tab.
112
Figure 7.2
The GNOME Mixer Applet
7.1.3 alsamixer
alsamixer can be run from the command line without the X environment, so is entirely
controlled via keyboard shortcuts. An alsamixer window always consists of the following
elements: a top row holding basic information on card and chip type, the selected view
type, and the mixer item then the volume bars below the information area. Use ← and
→ to scroll left or right if the controls cannot be displayed in one screen. The names
of the controls appear below the controls and the currently selected control is colored
in red. Toggle between muted and unmuted state of any mixer control using M . A
muted control has MM written below its name. Any control that has capture (recording)
capabilities has a red capture flag.
alsamixer has three different view modes: Playback, Capture, and All. By default, alsamixer is started in playback mode, displaying only those mixer controls relevant for
playback (Master Volume, PCM, CD, etc.). Capture displays only those controls used
for recording. All displays all controls available. Switch the view modes using F3 , F4 ,
and F5 .
Select channels with → and ← or N and P . Use ↑ and ↓ or + and - to increase and
decrease the volume. Stereo channels can be controlled independently, using Q , W ,
and E for increasing the volume and Z , X , and C for decreasing the volume. The
number keys between 0 and 9 can be used to change the absolute volume quickly.
These correspond to zero to ninety percent of full volume.
Sound in Linux
113
7.1.4 Look and Feel of Mixer Applications
The look and feel of mixer applications depends on the type of sound card used. Some
drivers, like SB Live!, have many controllable (tunable) mixer elements while the
drivers for professional sound cards may have elements with totally different names.
On-Board Sound Chip
Most of the PCI on-board sound chips are based on AC97 codec. Master controls the
main volume from the front speakers. Surround, Center, and LFE control the rear,
center, and bass-boost speakers. Each of them has a mute switch. In addition to that,
some boards have individual Headphone and Master Mono volumes. The latter is used
for the built-in speaker on some laptops.
PCM controls the internal volume level of digital WAVE playback. PCM is an acronym
for Pulse Code Modulation, one of the digital signal formats. This control has also an
individual mute switch.
Other volumes, like CD, Line, Mic, and Aux, control the loopback volume from the
corresponding input to the main output. They do not influence the recording level, only
the playback volumes.
For recording, turn on the Capture switch. This is the master recording switch. The
Capture volume is the input gain for recording. By default, this switch is set to zero.
Choose a recording source like Line or Mic. The recording source is exclusive, so you
cannot choose two of them at the same time. Mix is a special recording source. You
can record the currently played signal from this source.
Depending on the AC97 codec chip, special effects, like 3D or bass/treble, are available,
too.
SoundBlaster Live! and Audigy Family
SoundBlaster Live! and SB Audigy1 have numerous mixer controls for their AC97
codec chip and DSP engine. In addition to the controls already described, they have
Wave, Music, and AC97 volumes to control the internal signal routing and attenuation
for PCM, WaveTable MIDI, and AC97 mixing. Keep the volume at 100% to hear all
of them. SB Audigy2 (depending on the model) has less controls than SB Live, but still
has Wave and Music controls.
114
The recording on SB Live is similar to on-board chip. You can choose Wave and Music
as the additional recording source to record the played PCM and WaveTable signals.
USB Audio Devices
USB audio devices usually have a small number of mixer controls. Sometimes they
even have none at all. Most devices either have a Master or PCM control switch to
control the playback volume.
7.1.5 The Mixer for the Sound Chip Envy24
envy24control is a mixer application for sound cards using the Envy24 (ice1712) chip.
The flexibility of the Envy24 chip can result in varying functionalities in different sound
cards. The latest details on this sound chip are available in /usr/share/doc/
packages/alsa-tools/envy24control.
Figure 7.3
Monitor and Digital Mixer of envy24control
The Monitor Mixer of envy24control shows the signal levels that can be mixed digitally
in the sound card. The signals designated as PCM Out are generated by applications
that send PCM data to the sound card. The signals of the analog inputs are shown under
H/W In. The S/PDIF inputs are shown to the right. Set the input and output levels of
the analog channels under Analog Volume.
Use the Monitor Mixer sliders for digital mixing. The respective levels are displayed
in the Digital Mixer. For each output channel, the Patchbay contains a row of radio
buttons for selecting the desired channel source.
Sound in Linux
115
Adjust the amplification for the analog-to-digital and digital-to-analog converters under
Analog Volume. Use the DAC sliders for the output channels and the ADC sliders for
the input channels.
The S/PDIF channel settings are made under Hardware Settings. The Envy24 chip reacts
to volume changes with a delay that can be configured with Volume Change.
7.2 Multimedia Players
7.2.1 amaroK
The amaroK media player handles various audio formats and plays the streaming audio
broadcasts of radio stations on the Internet. The program handles all file types supported
by the sound server acting as a back-end—currently aRts or GStreamer.
On first start, amaroK launches a First-Run Wizard, which helps set up amaroK. In the
first step, configure your preferred look and feel for amaroK. Choose to display player
and playlist in separate windows (see Figure 7.4, “The amaroK Media Player” (page 117))
or combine their functionality in one single window. In the second step, determine
where amaroK should look for your music collection. amaroK scans these folders for
playable media. By default, amaroK is configured to scan the selected folders recursively
(to include all their subdirectories in the scan), monitor changes to the content of the
selected directories, and import any playlists located there. All the settings made with
the wizard can be modified later by starting the wizard again with Tools → First-Run
Wizard.
116
Figure 7.4
The amaroK Media Player
Managing Playlists
On start-up, amaroK scans the file system for multimedia files according to the settings
made in the wizard. The right part of the playlist window lists any playlists found. Play
titles listed in it in the order of your choice. If no playlist is found, create one. The best
way to do this is by using the sidebar to the left of the window. To the far left, there
are a number of tabs that can be used to open different views. From each of these views,
drag individual titles or entire directories and drop them into the playlist to include
them in the list. The following is a description of the function of each tab.
Context
With this tab, view information about your collection and the current artist. For
example, the view informs you about your favorite titles, the newest titles added to
the collection, and other details. The Home view provides statistics on your listening
habits, listing your favorite, newest, and least-played tracks. Current Track provides
data related to the track currently being played, such as the album cover (see Section
“The Cover Manager” (page 119)), the listening statistics related to this track, and
Sound in Linux
117
much more. If you are interested in the lyrics of the track, display them using the
Lyrics tab.
Collection Browser
Use this view to manage and display your personal collection of titles. The collection
view may include files from different locations. The wrench icon in the toolbar lets
you determine what locations should be scanned for music files. Once you select
the directories, the scan starts automatically. The result is displayed as a tree structure. Using Primary and Secondary, organize the two top branches of the tree according to the criteria Album, Artist, Genre, and Year. Once the tree view is ready,
find titles simply by typing them into the input field. The selection in the tree view
jumps to the first matching entry automatically as you type. To update your collection
data, initiate a rescan of the file system using Tools → Rescan Collection.
Playlist Browser
The playlist browser is divided into two parts. The upper part lists all your custom
playlists created by dragging tracks into the playlist window and clicking Save
Playlist As. View the contents of them by clicking the + next to the playlist's name.
Modify these playlists using drag and drop. To load one of them, double-click the
playlist.
IMPORTANT: Sharing Playlists with Other Players
Save playlists in m3u or pls format, so you can share them with any other
players using these formats.
amaroK can compile useful playlists (“Smart Playlists”) on the fly. Use the bottom
part of the playlist browser to select one of the smart playlists or click Create Smart
Playlist to define a custom smart playlist. Enter a name, search criteria, order, and
optional track limit.
File Browser
This tab opens a file browser. It corresponds to the standard KDE file selector dialog
with the usual controls for navigating the file system. Enter a URL or directory directly into the text input field. From the contents displayed, drag elements to the
playlist to include them. You can also perform a recursive search for a file in a
given directory. To do so, enter a text string for the title and the location at which
to start the search. Then select Search and wait for the results to appear in the lower
section of the window.
118
The Cover Manager
amaroK features a cover manager to enable you to keep matching music and image
data on the albums you play. Start the Cover Manager with Tools → Cover Manager.
A tree view in the left part of the window lists all the albums of your collection. The
covers retrieved from Amazon are displayed in the right part of the window. With View,
choose what is displayed in the cover list view. All albums lists all albums of your collection, regardless of whether they have a cover image. Albums with cover lists only
those with a cover and Albums without cover lists those lacking a cover. To retrieve
cover data, choose your Amazon Locale then click Fetch Missing Covers. amaroK then
tries to get covers for all albums contained in your collection.
Effects
Select the FX button in the player window or use the amaroK application menu to open
a dialog in which to enable and configure several sound effects, such as an equalizer,
the stereo balance, and a hall effect. Select the desired effects and adjust the settings,
if available, for each of them.
Visualizations
amaroK comes with a number of visualizations that display a graphical effect for the
music played. Native amaroK visualizations are displayed in the player window. Cycle
through the various available display modes by clicking the animation.
In addition to the above, amaroK also supports the visualization plug-ins of the XMMS
media player. To use these, first install the xmms-plugins package then select Visualizations from the amaroK menu. This opens a window listing the available plug-ins.
XMMS plug-ins are always displayed in an extra window. In some cases, there is an
option to display them in fullscreen mode. For some plug-ins, you may not get a smooth
visual effect unless you use a 3D-accelerated graphics card.
7.2.2 XMMS
XMMS is another full-featured media player with robust audio support, so that pops
or breaks during playback should be very rare. The application is easy to use. The button
for displaying the menu is located in the upper left corner of the program window. For
Sound in Linux
119
those preferring a GNOME-like look and feel, there is a GTK2 version of XMMS
available, the Beep Media Player. Just install the package bmp. However, not all XMMS
plug-ins are supported by this port of XMMS.
Figure 7.5 XMMS with Equalizer, OpenGL Spectrum Analyzer, and Infinity Plug-Ins
Select the output plug-in module with Options → Preferences → Audio I/O Plugins.
If the xmms-kde package is installed, the aRts sound server can be configured here.
IMPORTANT: Using the Disk Writer Plug-In
XMMS automatically redirects its output to the Disk Writer Plugin if it is not
able to find a configured sound card. In this case, the played files are written
to the hard disk as WAV files. The time display then runs faster than when
playing the output through a sound card.
Start various visualization plug-ins with Options → Preferences → Visualization Plugins. If you have a graphics card with 3D acceleration, select an application such as the
OpenGL spectrum analyzer. If the xmms-plugins package is installed, try the Infinity plug-in.
To the left under the menu button, there are five buttons with different letters on them.
These buttons allow quick access to additional menus, dialog, and configurations. Open
the playlist with PL and the equalizer with EQ.
120
7.3 CDs: Playback and Ripping
There are many ways to listen to your favorite music tracks. Either play a CD or play
digitalized versions of them. The following section features some CD player applications
as well as some applications that can be used for the ripping and encoding of audio
CDs.
IMPORTANT: CDDA and Analog CD Playback
There are two different ways of playing back audio CDs. CD and DVD drives
capable of analog CD playback read out the audio data and send it to the sound
output device. Some external drives connected via PCMCIA, FireWire, or USB
need to use CDDA (Compact Disk Digital Audio) to extract the audio data first
then play it as digital PCM. The players featured in the following sections do
not support CDDA. Use XMMS if you need CDDA support.
7.3.1 KsCD—Audio CD Player
KsCD is an easy-to-use audio CD player. It integrates into the KDE taskbar and can be
configured to start playing automatically after a CD has been inserted. To access the
configuration menu, select Extras → Configure KsCD. Fetch album and track information from a CDDB server on the Internet if KsCD is configured accordingly. You can
also upload CDDB information to share it with others. Use the CDDB dialog for information retrieval and upload.
Figure 7.6
The KsCD User Interface
Sound in Linux
121
7.3.2 GNOME CD Player Applet
This is a simple applet that integrates into a GNOME panel. Using the tools icon, configure its behavior and select a theme. Control the playback with the buttons at the
bottom of the player window or using the context menu opened by right-clicking the
panel icon or player window.
7.3.3 Compressing Audio Data
Audio compression can be handled by various tools. The following sections feature a
command-line approach to encoding and playing audio data as well as some graphical
applications capable of audio compression.
Command Line Tools for Encoding and Playback of
Audio Data
Ogg Vorbis (package vorbis-tools) is a free audio compression format that is now
supported by the majority of audio players and even portable MP3 players. The Web
page of the project is http://www.xiph.org/ogg/vorbis.
SUSE Linux comes with several tools supporting Ogg Vorbis. oggenc is a command
line tool used for encoding WAV files to Ogg. Just run oggenc myfile.wav to
transform a given .wav file into Ogg Vorbis. The option -h displays an overview of
the other parameters. Oggenc supports encoding with a variable bit rate. In this way,
an even higher degree of compression can be achieved. Instead of the bit rate, specify
the desired quality with the parameter -q; -b determines the average bit rate; -m and
-M specify the minimum and maximum bit rate.
ogg123 is a command-line Ogg player. Start it with a command like ogg123
mysong.ogg.
Compressing Audio Data Using Grip
Grip is a GNOME CD player and ripper (see Figure 7.7, “Ripping Audio CDs with
Grip” (page 123)). The CD player functionality is entirely controlled by the buttons in
the bottom part of the window. Control the ripping and encoding functionality using
the tabs at the top of the window. To view and edit the track and album information or
122
to select the tracks to rip, open the Tracks tab. Select a track by clicking the check box
next to the track title. To edit the track information, click Toggle disc editor and submit
your modifications. The Rip tab selects the preferred rip mode and controls the ripping
process. Access the entire Grip configuration under the Config tab. Use Status to check
the status of the application.
Figure 7.7
Ripping Audio CDs with Grip
Compressing Audio Data Using KAudioCreator
KAudioCreator is a lean CD ripper application (see Figure 7.8, “Ripping Audio CDs
with KAudioCreator” (page 124)). Once started, it lists all the tracks of your CD in the
CD Tracks tab. Select the tracks to rip and encode. To edit the track information, use
the Album Editor under File → Edit Album. Otherwise just start the ripping and encoding
with File → Rip Selection. Watch the progress of these jobs using the Jobs tab. If configured accordingly, KAudioCreator also generates playlist files for your selection that
can be used by players, like amaroK or XMMS.
Sound in Linux
123
Figure 7.8
Ripping Audio CDs with KAudioCreator
Compressing Audio CDs Using Konqueror
Before you start the actual ripping process with Konqueror, configure the handling of
audio CDs and the Ogg Vorbis encoder in the KDE Control Center. Select Sound &
Multimedia → Audio CDs. The configuration module is divided into three tabs: General,
Names, and Ogg Vorbis Encoder. Normally, a suitable CD device is detected automatically. Do not change this default setting unless the autodetection failed and you need
to set the CD device manually. Error correction and encoder priority can also be set
here. The tab Ogg Vorbis Encoder determines the quality of the encoding. To configure
online lookup of album, track, and artist information for your ripped audio data, select
Add Track Information.
Start the ripping process by inserting the CD into the CD-ROM drive and enter
audiocd:/ at the Location bar. Konqueror then lists the tracks of the CD and some
folders (see Figure 7.9, “Ripping Audio Data with Konqueror” (page 125)).
124
Figure 7.9
Ripping Audio Data with Konqueror
To keep uncompressed audio data on your disk, just select the .wav files and drag
them into another Konqueror window to copy them over to their final destination. To
start the Ogg Vorbis encoding, drag the Ogg Vorbis folder to another Konqueror
window. The encoding starts as soon as you drop the Ogg Vorbis folder to its destination.
7.4 Hard Disk Recording with
Audacity
With audacity (package audacity), record and edit audio files. This is called hard
disk recording. When you start the program for the first time, select a language. At
other times, change the language setting under File → Preferences → Interface. The
language change is then effective the next time you start the program.
Sound in Linux
125
Figure 7.10
Spectral View of the Audio Data
7.4.1 Recording WAV Files and Importing
Files
Click the red recording button to create an empty stereo track and start the recording.
To change the standard parameters, make the desired settings under File → Preferences.
Audio I/O and Quality are important for the recording. Even if tracks already exist,
pressing the recording button creates new tracks. Initially, this may be confusing, because
these tracks cannot be seen in the standard-size program window.
To import audio files, select Project → Import Audio. The program supports the WAV
format and the compressed Ogg Vorbis format. See Section 7.3.3, “Compressing Audio
Data” (page 122) for more information about this format.
7.4.2 Editing Audio Files
Open the AudioTrack menu to the left of the track. This menu offers various options
for different views and basic editing operations. To rename the track, select Name and
126
enter a new name. The different view modes offered by Audacity include Waveform,
Waveform (dB), Spectrum, and Pitch. Choose the one suiting your needs. If you want
to edit each channel of a stereo track separately, select Split Track. Each channel can
then be treated as a separate track. Set Sample Format (in bit) and Sample Rate (in Hz)
for each track.
Before you can use most of the tools offered in the Edit menu, first select the channel
and the segment of the track to edit. After making your selection, you can apply all
kinds of modifications and effects to it.
Depending on the chosen file type, various view formats for segment selections are
offered under View → Set Selection Format. With Set Snap-To Mode, the segment
boundaries can automatically be adapted to the selected view format. For example, if
you select PAL frames as the view format and activate Snap-To, the segment boundaries
are always selected in multiples of frames.
All editing tools come with tool tips, so should be easy to use. The Undo History
function, accessed with View → History, is a useful feature for viewing recent editing
steps and undoing them by clicking in the list. Use Discard with caution, because it
deletes editing steps from the list. Once discarded, these steps can no longer be undone.
Figure 7.11
The Spectrum
The built-in spectrum analyzer assists in quickly tracking down any noises. View the
spectrum of the selected segment with View → Plot Spectrum. Select a logarithmic
Sound in Linux
127
frequency scale in octaves with Log frequency. If you move the mouse pointer within
the spectrum, the frequencies of the peaks are automatically displayed together with
the respective notes.
Remove unwanted frequencies with Effect → FFT Filter. In connection with the filtering
process, it may be necessary to readjust the signal amplitude with Amplify. Additionally,
use Amplify to check the amplitude. By default, the New Peak Amplitude is set to 0.0
dB. This value represents the highest possible amplitude in the selected audio format.
Amplification shows the value needed to amplify the selected segment to this peak
amplitude. A negative value indicates overamplification.
7.4.3 Saving and Exporting
To save the entire project, select File → Save Project or Save Project As. This generates
an XML file with the extension .aup, which describes the project. The actual audio
data is saved in a directory named after the project with _data appended.
The entire project or the currently selected segment can also be exported as a stereo
WAV file. To export the project in Ogg Vorbis format, refer to the information in
Section 7.3.3, “Compressing Audio Data” (page 122).
7.5 Direct Recording and Playback
of WAV Files
arecord and aplay from the alsa package provide a simple and flexible interface
to the PCM devices. arecord and aplay can be used to record and play audio data
in the WAV format and other formats. The command arecord -d 10 -f cd -t
wav mysong.wav records a WAV file of 10 seconds in CD quality (16 bit, 44.1
kHz). List all options of arecord and aplay by running them with the --help
option.
qaRecord (package kalsatools) is a simple recording program with a graphical interface and level display. Because this program uses an internal buffer of about 1 MB
(configurable with --buffersize), it enables uninterrupted recordings even on slow
hardware, especially if it is run with real-time priority. During the recording, the cur-
128
rently-used buffer size is displayed in the status line under Buffer and the maximum
buffer size required so far for this recording is displayed under Peak.
Figure 7.12
QARecord—A Simple Hard Disk Recording Application
Sound in Linux
129
TV, Video, Radio, and Webcam
8
This chapter introduces some basic Linux video, radio, and webcam applications. Learn
how to configure and use motv for watching analog TV, using a webcam, and browsing
video text. Use xawtv4 for digital video broadcasts. Webcams can be run using gqcam.
EPG information can be accessed using nxtvepg or xawtv4.
8.1 Watching TV with motv
motv is an improved successor to xawtv. It incorporates all essential functions into the
user interface. Start the application with Multimedia → Video → motv. Start it at the
command line with motv. Initially, only a TV window appears after the application
starts. Open a menu window by right-clicking it.
TV, Video, Radio, and Webcam
131
Figure 8.1
The TV Application motv
8.1.1 Video Source and Network Search
In Settings → Input, select the video source. If you select Television here, set up the
broadcasting network before starting the application. This automatically takes place
with the network search, also found under the Settings menu. If you click Save settings,
the network found is entered into the .xawtv file in your home directory and will be
available the next time you start the application.
TIP: Selecting Channels
If you do not want to browse for all available channels, find the next channel
with Ctrl + ↑ . If needed, subsequently adjust the broadcast frequency with ←
or → .
8.1.2 Retrieving Audio Data
The audio output of the TV card is connected to the line input of your sound card, to
the speakers, or to an amplifier. Some TV cards can change the volume of the audio
output. The volume can then be set with the sliders that appear after selecting Settings
→ Slider. This window also provides the sliders for brightness, contrast, and color.
132
To use your sound card for audio playback, check the mixer settings using gamix, described in Section 7.1, “Mixers” (page 111). For sound cards meeting the AC97 specifications, set Input-MUX to Line. The volume can then be adjusted with the Master and
Line sliders.
8.1.3 Screen Proportions and Full-Screen
Mode
Most television images have a height and width ratio of 4:3. These proportions can be
set with Tools → Screen Dimensions. If 4:3 is selected here (this is the default setting),
the screen dimensions are retained automatically, even when the display size is changed.
With F or Tools → Fullscreen, switch to full-screen mode. If the TV image in fullscreen mode is not scaled to the full monitor size, some fine-tuning is required. Many
graphics cards can scale the full-screen mode television image to the full monitor size
without changing the graphical mode. If your card does not support this function, the
graphics mode must be switched to 640x480 for the full-screen mode. Create the related
configuration in Settings → Configuration. After restarting motv, the monitor mode is
also changed if you have switched to full-screen mode.
TIP: Storing the Configuration in .xawtv
The .xawtv file is created automatically and updated by clicking Settings →
Save settings. Here, the broadcasters are saved along with the configuration.
More information about the configuration file can be found in the man page
for xawtvrc.
8.1.4 The Launcher Menu
Use the launcher menu to start other applications to use with motv. Start the audio
mixer gamix and the video text application alevt, for example, using a keyboard shortcut.
Applications to launch from motv must be entered in the .xawtv file. The entries
should look like this:
[launch] Gamix = Ctrl+G, gamix AleVT = Ctrl+A, alevt
The shortcut then the command used to start the application should follow the application
name itself. Start the applications entered under [launch] via the Tool menu.
TV, Video, Radio, and Webcam
133
8.2 Video Text Support
Use alevt to browse video text pages. Start the application with Multimedia → Video
→ alevt or at the command line with alevt.
The application saves all the pages of the selected station just activated with motv.
Browse pages by entering the desired page number or by clicking a page number. Move
forward or backward through the pages by clicking << or >>, located in the lower
window margin.
Recent versions of motv and its successor xawtv4 include their own video text viewer
applications: mtt (motv) and mtt4 (xawtv4). mtt4 even supports DVB cards.
8.3 Webcams and motv
If your webcam is already supported by Linux, access it with motv. Find a summary
of the supported USB devices at http://www.linux-usb.org. If you have already
used motv to access the TV card prior to accessing the webcam, the bttv driver is
loaded. The webcam driver is loaded automatically when your webcam is connected
to the USB. Start motv at the command line with the parameter -c /dev/video1
to access the webcam. Access the TV card with motv -c /dev/video0.
When connecting the webcam to the USB before the bttv driver has been automatically
loaded (for example, by starting a TV application), /dev/video0 is reserved for the
webcam. In this case, if you start motv with the -c /dev/video1 parameter to access
the TV card, you might get an error message, because the bttv driver was not automatically loaded. Solve this problem by loading the driver separately with modprobe
bttv as the user root. Access an overview of the configurable video devices on your
system with motv -hwscan.
8.4 nxtvepg—The TV Magazine for
Your PC
From some broadcasters, an EPG signal (Electronic Program Guide) is transmitted
along with the video text signal. Easily view this electronic guide using the program
134
nxtvepg. To do this, however, you must have a TV card supported by the bttv driver
and be able to receive one of the channels broadcast with an EPG.
With nxtvepg, the broadcasts are sorted according to channel and topic, such as movie
and sport, and filtered according to criteria, such as Live, Stereo, or Subtitle. Start the
application with Multimedia → Video → nxtvepg or at the command line with nxtvepg.
8.4.1 Importing the EPG Database
To set up and update the program database via the EPG signal, set the tuner of your
TV card to a station that broadcasts EPG. This can be done using a TV application,
such as motv or nxtvepg. Only one application at a time can access the tuner.
If you set an EPG broadcaster in motv, nxtvepg immediately begins importing the
current list of TV programs. The progress is displayed.
Figure 8.2
The Electronic TV Magazine nxtvepg
TV, Video, Radio, and Webcam
135
If you have not started a TV application, let nxtvepg search for EPG broadcasters. To
do this, use Configure → Provider scan. Use .xatv is activated by default. This indicates
that nxtvepg is accessing the broadcasters saved in this file.
TIP: Troubleshooting
If there are problems, check to see if the proper video source has been chosen
under TV card input.
Select from the EPG providers found in Configure → Select Provider. Configure →
Merge Providers even creates flexible associations between the various provider
databases.
8.4.2 Sorting the Programs
nxtvepg provides a convenient filter function for managing even the most extensive
program offerings. Activate a network selection list with Configure → Show networks.
The Filter menu offers plenty of filter functions. Right-click the program list to open
a special filter menu in which to activate contextual filter functions.
Of particular interest is the Navigate menu. This is built directly from the EPG data. It
appears in the language provided by the network.
8.5 Watching Digital Video
Broadcasts with xawtv4
As your hardware has been properly configured with YaST, start xawtv4 from the main
menu (Multimedia → Video → xawtv4 ). Before you can actually start watching your
favorite broadcasts, build a database of DVB stations.
136
Figure 8.3
Running xawtv4
Right-click the start window to open the control window (see Figure 8.3, “Running
xawtv4” (page 137)). Start a scan for available DVB stations with Edit → Scan DVB.
A channel scanner and browser window open. Select a bouquet to prepare the scan.
This can be done manually with Commands → Tune manually if you already know the
tuning parameters of the bouquet or by requesting them from a built-in database of
xawtv4 via Database → _country_ → _channel number_ (replace _country_ and
_channel_number_) by the actual values for your location.
As soon as the scanner is tuned-in, the first data is displayed in the browser window.
Launch a full scan of all available stations with Command → Full Scan. While the
scanner is running, you can select your favorite stations and add them to the station list
by simply dragging them into the control window. Leave the channel scanner and select
one of the channels to start watching the broadcast.
TIP: Editing the Station List
Using keyboard shortcuts, control the channel selection using your keyboard.
To set a shortcut for any station contained in your station list, select the station,
click Edit → Edit Station. A dialog called TV Station Properties opens. Enter the
shortcut and leave the dialog with OK. This dialog also allows you to define
submenus holding groups of stations (such as “news” or “private”).
TV, Video, Radio, and Webcam
137
The xawtv4 software package contains several more useful stand-alone multimedia
applications:
pia4
A lean command-line–controlled movie player that can be used to play any movie
streams recorded by xawtv4.
mtt4
A video text browser (see Figure 8.4, “The mtt4 Video Text Browser” (page 138)).
Figure 8.4
The mtt4 Video Text Browser
alexplore
A stand-alone DVB channel scanner application. Its functionality is integrated into
xawtv4.
dvbradio
A DVB radio player. Use it to listen to DVB-S radio streams after you have completed the initial station scan (see Figure 8.5, “DVB Radio” (page 139)).
138
Figure 8.5
DVB Radio
dvbrowse
An EPG browser application. Use it to get EPG information after you have completed
the initial station scan.
TV, Video, Radio, and Webcam
139
K3b—Burning CDs or DVDs
9
K3b is a comprehensive program for writing data and audio CDs and DVDs. Start the
program from the main menu or by entering the command k3b. The following sections
brief you on how to start a basic burning process to get your first Linux-made CD or
DVD.
9.1 Creating a Data CD
To create a data CD, go to File → New Project → New Data Project. The project view
appears in the lower part of the window, as shown in Figure 9.1, “Creating a New Data
CD” (page 142). Drag the desired directories or individual files from your home directory to the project folder and drop them there. Save the project under a name of your
choice with File → Save as.
K3b—Burning CDs or DVDs
141
Figure 9.1
Creating a New Data CD
Then select Burn from the toolbar or hit Ctrl + B . A dialog with six tabs offering various
options for writing the CD opens. See Figure 9.2, “Customizing the Burning Process”
(page 142).
Figure 9.2
142
Customizing the Burning Process
The Writing tab has various settings for the burning device, the speed, and the burning
options. The following options are offered here:
Burning Device
The detected writer is displayed under this pop-up menu. You can select the speed
here too.
WARNING: Select Writing Speed with Care
Normally, you should select Auto, which chooses the maximum writing
speed possible. However, if you increase this value but your system is not
able to send the data fast enough, the likelihood of buffer underruns increases.
Writing Mode
This option determines how the laser writes a CD. In DAO (disk at once) mode, the
laser is not deactivated while the CD is written. This mode is recommended for the
creation of audio CDs. However, it is not supported by all CD writers. In the TAO
mode (track at once), a separate write process is used for each individual track. The
RAW mode is not used very often, because the writer does not perform any data
corrections. The best setting is Auto, because it allows K3b to use the most suitable
settings.
Simulate
This function can be used to check if your system supports the selected writing
speed. The writing is performed with the laser deactivated to test the system.
On the Fly
Burns the desired data without first creating an image file (do not use this feature
on low-performance machines). An image file—also known as an ISO image—is
a file containing the entire CD content that is subsequently written to the CD exactly
as it is.
Only Create Image
This option creates an image file. Set the path for this file under Temporary File.
The image file can be written to CD at a later time. To do this, use Tools → CD →
Burn CD Image. If this option is used, all other options in this section are deactivated.
Remove Image
Remove the temporary image file from hard disk when finished.
K3b—Burning CDs or DVDs
143
Verify Written Data
Check the integrity of the written data by comparing the MD5 sums of the original
and the burned data.
The Image tab is only accessible if the option Only create image from the previous tab
is selected. If this is the case, you can determine the file where the ISO is written.
The Settings tab contains two options: Datatrack Mode and Multisession Mode. The
Datatrack Mode options contains configuration of how data tracks may be written. In
general, auto is considered the best suited method. The Multisession Mode is used to
append data to a already written, but not finalized, CD.
In the Volume Desc tab, enter some general information that can be used to identify
this particular data project, its publisher and preparer, and the application and operating
system used in the creation of this project.
Under File system, specify settings for the file system on the CD (RockRidge, Joliet,
UDF). Also determine how symbolic links, file permissions, and blanks are treated. In
the Advanced tab, experienced users can make additional settings.
After adjusting all settings to your needs, start the actual burning process using Burn.
Alternatively, save these settings for future use and adjustment with Save.
9.2 Creating an Audio CD
Basically, there are no significant differences between creating an audio CD and creating
a data CD. Select File → New Audio Project. Drag and drop the individual audio tracks
to the project folder. The audio data must be in WAV or Ogg Vorbis format. Determine
the sequence of the tracks by moving them up or down in the project folder.
With the help of CD Text, you are able to add certain text information to a CD, such
as CD title, artist name, and track name. CD players that support this feature can read
and display this information. To add CD Text information to your audio tracks, select
the track first. Right-click and select Properties. A new window opens in which to enter
your information.
The dialog for burning an audio CD is not very different from the dialog for burning a
data CD. However, the Disc at once and the Track at once modes have greater importance. The Track at once mode inserts an intermission of two seconds after each track.
144
TIP: Preserving Data Integrity
When burning audio CDs, choose a lower burning speed to reduce the risk of
burning errors.
After adjusting all settings to your needs, start the actual burning process using Burn.
Alternatively, save these settings for future use and adjustment with Save.
9.3 Copying a CD or DVD
Select Tools → Copy CD or Tools → Copy DVD depending on your media. In the dialog
that opens, make the settings for the reading and writing device as shown in Figure 9.3,
“Copying a CD” (page 145). The writing options discussed are also available here. An
additional function enables the creation of several copies of the CD or DVD.
Figure 9.3
Copying a CD
K3b—Burning CDs or DVDs
145
Check On the fly to burn the CD as soon as it has been read or select Only create image
to create an image in the path specified in Temp Directory → Write image file to and
burn the image later.
9.4 Writing ISO Images
If you already have an ISO image, go to Tools → CD → Burn CD image. A window
opens in which to enter the location of the Image to Burn. K3b calculates a check sum
and displays it in MD5 Sum. If the ISO file was downloaded from the Internet, this sum
shows if the download was successful.
Use the Options and Advanced tabs to set your preferences. To burn the CD, click Start.
9.5 Creating a Multisession CD or
DVD
Multisession discs can be used to write data in more than one burning session. This is
useful, for example, for writing backups that are smaller than the media. In each session,
you can add another backup file. The interesting part is that you are not only limited to
data CDs or DVDs. You can also add audio sessions in a multisession disc.
To start a new multisession disc, do the following:
1 Create your data disc first and add all your files. You cannot start with an audio
CD session. Make sure that you do not fill up the whole disc, because otherwise
you cannot append a new session.
2 Burn your data with Project → Burn. A dialog box appears.
3 Go to the tab Settings and select Start Multisession.
4 Configure other options if needed. See also Section 9.1, “Creating a Data CD”
(page 141).
5 Start the buring session with Burn.
146
After a successful burning process, you have created a multisession disc. As long as
the media contains enough space, you can append more sessions if you like. Finish
discs only if you are sure you do not need any new sessions or the space is occupied.
NOTE: About Storage Space on Multisession Discs
Be aware that multisession discs need space for bookkeeping all the entries
from your sessions. This leads to a smaller amount of available space on your
disc. The amount depends on the number of sessions.
9.6 For More Information
Apart from the two main functions described above, K3b offers other functions, such
as the creation of DVD copies, reading audio data in WAV format, rewriting CDs, and
playing music with the integrated audio player. A detailed description of all available
program features is available at http://k3b.sourceforge.net.
K3b—Burning CDs or DVDs
147
Part IV Office
The OpenOffice.org Office Suite
10
OpenOffice.org is a powerful office suite that offers tools for all types of office tasks,
such as writing texts, working with spreadsheets, or creating graphics and presentations.
With OpenOffice.org, use the same data across different computing platforms. You can
also open and edit files in Microsoft Office formats then save them back to this format,
if needed. This chapter only covers the basic skills needed to get started with OpenOffice.org. Start the application from the SUSE menu or using the command ooffice.
OpenOffice.org consists of several application modules (subprograms), which are designed to interact with each other. They are listed in Table 10.1, “The OpenOffice.org
Application Modules” (page 151). The discussion in this chapter is focused on Writer.
A full description of each module is available in the online help, described in Section 10.6, “For More Information” (page 157).
Table 10.1
The OpenOffice.org Application Modules
Writer
Powerful word processor application
Calc
Spreadsheet application that includes a chart utility
Draw
Drawing application for creating vector graphics
Math
Application for generating mathematical formulas
Impress
Application for creating presentations
Base
Database application
The OpenOffice.org Office Suite
151
The appearance of the application varies depending on which desktop or window
manager is used. Additionally, the open and save dialog formats for your desktop are
used. Regardless of the appearance, the basic layout and functions are the same.
10.1
Compatibility with Other Office
Applications
OpenOffice.org is able to work with Microsoft Office documents, spreadsheets, presentations, and databases. They can be seamlessly opened like other files and saved back
to that format. Because the Microsoft formats are closed and the specifics are not
available to other applications, there are occasionally formatting issues. If you have
problems with your documents, consider opening them in the original application and
resaving in an open format, such as RTF for text documents or CSV for spreadsheets.
To convert a number of documents, such as when first switching to the application,
select File → Wizard → Document Converter. Choose the file format from which to
convert. There are several StarOffice and Microsoft Office formats available. After
selecting a format, click Next then specify where OpenOffice.org should look for templates and documents to convert and in which directory the converted files should be
placed. Before continuing, make sure that all other settings are appropriate. Click Next
to see a summary of the actions to perform, which gives another opportunity to check
whether all settings are correct. Finally, start the conversion by clicking Convert.
IMPORTANT: Finding Windows Files
Documents from a Windows partition are usually in a subdirectory of
/windows.
When sharing documents with others, you have several options. If the recipient only
needs to read the document, export it to a PDF file with File → Export as PDF. PDF
files can be read on any platform using a viewer like Adobe Acrobat Reader. To share
a document for editing, use one of the regular document formats. The default formats
comply with the OASIS standard XML format, making them compatible with a number
of applications. TXT and RTF formats, although limited in formatting, might be a good
option for text documents. CSV is useful for spreadsheets. OpenOffice.org might also
offer your recipient's preferred format, especially Microsoft formats.
152
OpenOffice.org is available for a number of operating systems. This makes it an excellent
tool when a group of users frequently need to share files and do not use the same system
on their computers.
10.2
Figure 10.1
Word Processing with Writer
The OpenOffice.org Writer
There are two ways to create a new document. To create a document from scratch, use
File → New → Text Document. To use a standard format and predefined elements for
your own documents, try a wizard. Wizards are small utilities that let you make some
basic decisions then produce a ready-made document from a template. For example,
to create a business letter, select File → Wizards → Letter. Using the wizard's dialogs,
easily create a basic document using a standard format. A sample wizard dialog is
shown in Figure 10.2, “An OpenOffice.org Wizard” (page 154).
The OpenOffice.org Office Suite
153
Figure 10.2
An OpenOffice.org Wizard
Enter text in the document window as desired. Use the Formatting toolbar or the Format
menu to adjust the appearance of the document. Use the File menu or the relevant buttons
in the toolbar to print and save your document. With the options under Insert, add extra
items to your document, such as a table, picture, or chart.
10.2.1 Selecting Text
To select text, click the desired beginning of the selection and, keeping the mouse button
pressed, move the cursor towards the end of the range (which can be characters, lines,
or entire paragraphs). Release the button when all desired text is selected. While selected,
text is displayed in inverted colors. Open a context menu by right-clicking the selection.
Use the context menu to change the font, the font style, and other text properties.
Selected text can be cut or copied to the clipboard. Cut or copied text can be pasted
back into the document at another location. Use the context menu, Edit, or the relevant
toolbar icons to access these functions.
154
10.2.2 Navigating in Large Documents
The Navigator displays information about the contents of a document. It also enables
you to jump quickly to the different elements included. For example, use the Navigator
to get a quick overview of all the chapters or to see a list of the images included in the
document. Open it by selecting Edit → Navigator. Figure 10.3, “The Navigator in
Writer” (page 155) shows the Navigator in action. The elements listed in the Navigator
vary according to the document loaded in Writer.
Figure 10.3
The Navigator in Writer
10.2.3 Formatting with Styles
The dialog opened with Format → Styles and Formatting can help you format text in
a number of ways. If you set the drop-down list at the bottom of this dialog to Automatic,
OpenOffice.org tries to offer a selection of styles adapted to the task at hand. If you
select All Styles, the Stylist offers all styles from the currently active group. Select
groups with the buttons at the top.
By formatting your text with this method, called soft formatting, text is not formatted
directly. Instead, a style is applied to it. The style can be modified easily, automatically
resulting in a formatting change of all the text to which it is assigned.
The OpenOffice.org Office Suite
155
To assign a style to a paragraph, select the style to use then click the paint bucket icon
in Styles and Formatting. Click the paragraphs to which to assign the style. Stop assigning the style by pressing Esc or clicking the paint bucket icon again.
Easily create your own styles by formatting a paragraph or a character as desired using
the Format menu or toolbar. Select the formatted item from which to copy the style.
Then click and hold the button to the right of the bucket in Styles and Formatting and
select New Style from Selection from the menu that opens. Enter a name for your style
and click OK. This style can then be applied to other texts.
Change details of a style by selecting it in the list, right-clicking, and selecting Modify
from the menu. This opens a dialog in which all the possible formatting properties are
available for modification.
10.3
Introducing Calc
Calc is OpenOffice.org's spreadsheet application. Create a new spreadsheet with File
→ New → Spreadsheet or open one with File → Open. Calc can read and save in Microsoft Excel's format.
In the spreadsheet cells, enter fixed data or formulas. A formula can manipulate data
from other cells to generate a value for the cell in which it is inserted. You can also
create charts from cell values.
10.4
Introducing Impress
Impress is designed for creating presentations for screen display or printing, such as
on transparencies. Create a presentation from scratch with File → New → Presentation.
To create one with the assistance of a wizard, use File → Wizards → Presentation.
Open an existing presentation with File → Open. Impress can open and save Microsoft
PowerPoint presentations.
156
10.5
Introducing Base
OpenOffice 2.0 introduces a new database module. Create a database with File → New
→ Database. A wizard opens to assist in creating the database. Base can also work
with Microsoft Access databases.
Figure 10.4
Base—Databases in OpenOffice.org
Tables, forms, queries, and reports can be created manually or using convenient wizards.
For example, the table wizard contains a number of common fields for business and
personal use. Databases created in Base can be used as data sources, such as when
creating form letters.
10.6
For More Information
OpenOffice.org includes a number of information options that provide different levels
of information. To get thoroughly acquainted with a topic, select Help → OpenOffice.org
Help. The help system provides in-depth information about each of the modules of
OpenOffice.org (Writer, Calc, Impress, etc.).
The OpenOffice.org Office Suite
157
When the application is first started, it provides Tips, short information about buttons
when the mouse hovers over them, and the Help Agent, information based on actions
performed. To get more extensive information about buttons than the Tips provide, use
Help → What's This then hover over the desired buttons. To end What's This mode,
click. If you frequently need this function, consider enabling the Extended Tips in Tools
→ Options → OpenOffice.org → General. The Help Agent and Tips can also be enabled
and disabled here.
The OpenOffice.org Web site is http://www.openoffice.org. There, find
mailing lists, articles, and bug information. This site provides the versions for various
operating systems for download.
158
Evolution: An E-Mail and Calendar
Program
11
Evolution is a groupware suite that offers the usual e-mail features along with extended
features, like task lists and a calendar. The application also provides a complete address
book that includes the ability to send contact information to others in vCard format.
Start Evolution from the main menu or with evolution. When started for the first
time, Evolution offers a configuration assistant. Its use is described in Section 11.3.1,
“Configuring Accounts” (page 161).
IMPORTANT: Microsoft Exchange Accounts
To use Evolution with Microsoft Exchange, you must install the
ximian-connector package. Install it with YaST.
11.1
Importing E-Mail from Other
Mail Programs
To import e-mail from other e-mail programs, such as Netscape, select File → Import.
For mbox formats, select Import a single file. For Netscape, select Import data and
settings from older programs. To work with data from programs using the maildir format,
such as KMail, configure an account that accesses the mail directory.
Evolution: An E-Mail and Calendar Program
159
11.2
Evolution Overview
The default window view is shown in Figure 11.1, “The Evolution Window with Mail”
(page 160). The available menus, menu items, and the icons in the toolbar vary depending
on the open component. Use the left frame to select which information to display in
the right frame. Adjust the size of the frames by dragging the dividing bars.
Figure 11.1
The Evolution Window with Mail
11.2.1 Mail
In this view, the upper half of the window shows the contents of the current folder. The
lower half is a preview pane used to display the selected mail message. To display a
different folder, select a folder from the folder list in the left frame.
Use the search bar to search the messages in a folder. To sort messages by a table
header, click the desired header. The arrow to the right shows whether the column is
sorted in ascending or descending order. Click the column header until the messages
are sorted in the desired direction.
160
11.2.2 Contacts
This view shows all the addresses in your address book. To locate a particular address,
use the search bar or click the button to the right displaying the first letter of the contact's
last name. Add contacts or lists with the toolbar.
11.2.3 Calendar
The initial display shows a view of the current day with the month and a task list shown
in an additional pane to the right. Week, work week, and month views are also available
from the toolbar or the View menu. Use the search bar to find an appointment that has
been entered in the calendar. Add appointments and tasks using the buttons in the
toolbar. You can also use the toolbar to page through the calendar or jump to a specific
date.
11.2.4 Tasks
Tasks provides a list of tasks. Details of the selected task are shown in the lower part
of the window. Use File → New → Task to add a new task. Search the tasks with the
search bar. Assign tasks to others by right-clicking the task and selecting Assign Task.
Open the task to add more details, such as a due date and completion status.
11.3
Mail
The Evolution mail component can work with multiple accounts in a variety of formats.
It offers useful features, such as virtual folders for showing search results and filtering
for junk mail. Configure the application in Edit → Preferences.
11.3.1 Configuring Accounts
Evolution can retrieve e-mail from multiple mail accounts. The account you want to
send e-mail from can be selected when you compose a message. Configure mail accounts
in Edit → Preferences → Mail Accounts. To modify an existing configuration, select
it and click Edit. To delete an account, select it and click Delete.
Evolution: An E-Mail and Calendar Program
161
To add a new account, click Add. This opens the configuration assistant. Click Forward
to use it. Enter your name and your e-mail address in the respective fields. Enter the
optional information if desired. Check Make this my default account to use this account
by default when writing mails. Click Forward.
Select the appropriate incoming e-mail format for this address in Server Type. POP is
the most common format for downloading mail from a remote server. IMAP works
with mail folders on a special server. Obtain this information from your ISP or server
administrator. Complete the other relevant fields displayed when the server type is selected. Click Forward when finished. Select the desired Receiving Options, if available.
Click Forward.
Next, configure the mail delivery options. To submit outgoing e-mail to the local system,
select Sendmail. For a remote server, select SMTP. Get the details from your ISP or
server administrator. For SMTP, complete the other fields displayed after selection.
Click Forward when finished.
By default, the e-mail address is used as the name to identify the account. Enter another
name if desired. Click Forward. Click Apply to save your account configuration.
To make an account the default account for sending e-mail, select the desired account
then press Default. To disable the retrieving of e-mail from an account, select the account
then click Disable. A disabled account can still be used as the address for sending, but
that account is not checked for incoming e-mail. If necessary, reactivate the account
with Enable.
11.3.2 Creating Messages
To compose a new message, click New → Mail Message. Replying to or forwarding a
message opens the same message editor. Next to From, select from which account to
send the message. In the recipient fields, enter an e-mail address or part of a name or
address in your address book. If Evolution can match what you enter to something in
the address book, a selection list is displayed. Click the desired contact or complete
your input if there are no matches. To select a recipient directly from the address book,
click To or CC.
Evolution can send e-mail as plain text or HTML. To format HTML mail, select Format
in the toolbar. To send attachments, select Attach or Insert → Attachment.
162
To send your message, click Send. If not ready to send it immediately, make another
selection under File. For example, save the message as a draft or send it later.
11.3.3 Encrypted E-Mail and Signatures
Evolution supports e-mail encryption with PGP. It can sign e-mail and check signed email messages. To use these features, generate and manage keys with an external application, such as gpg or KGpg.
To sign an e-mail message before sending it, select Security → PGP sign. When you
click Send, a dialog prompts for the password of your secret key. Enter the password
and exit the dialog with OK to send the signed e-mail. To sign other e-mail messages
in the course of this session without needing to “unlock” the secret key repeatedly,
check Remember this password for the remainder of this session.
When you receive signed e-mail from other users, a small padlock icon appears at the
end of the message. If you click this symbol, Evolution starts an external program (gpg)
to check the signature. If the signature is valid, a green check mark appears next to the
padlock symbol. If the signature is invalid, a broken padlock appears.
The encryption and decryption of e-mail is just as easy. After composing the e-mail
message, go to Security → PGP encrypt and send the e-mail message. When you receive
encrypted messages, a dialog asks for the password of your secret key. Enter the
passphrase to decrypt the e-mail message.
11.3.4 Folders
It is often convenient to sort e-mail messages into a variety of folders. Your folder tree
is shown in the left frame. If accessing mail over IMAP, the IMAP folders are also
shown in this folder bar. For POP and most other formats, your folders are stored locally,
sorted under Local Folders.
Several folders are included by default. Inbox is where new messages fetched from a
server are initially placed. Sent is used for saving copies of sent e-mail messages. The
Outbox provides temporary storage for e-mail that has not yet been sent. It is useful if
working offline or if the outgoing mail server is temporarily unreachable. Drafts is used
for saving unfinished e-mail messages. The Trash folder is intended for temporary
storage of deleted items. Junk is for Evolution's junk mail filtering feature.
Evolution: An E-Mail and Calendar Program
163
New folders can be created under On This Computer or as subfolders of existing folders.
Create as complex a folder hierarchy as desired. To create a new folder, select File →
New → Mail Folder. In the Mail Folder dialog, enter a name for the new folder. Use
the mouse to determine the parent folder under which to place the new folder. Exit the
dialog with OK.
To move a message into a folder, select the message to move. Right-click to open the
context menu. Select Move to Folder and, in the dialog that opens, the destination
folder. Click OK to move the message. The message header in the original folder is
shown with a line through it, meaning that message is marked for deletion from that
folder. The message is stored in the new folder. Messages can be copied in a similar
manner.
Manually moving a number of messages into different folders can be time-consuming.
Filters can be used to automate this procedure.
11.3.5 Filters
Evolution offers a number of options for filtering e-mail. Filters can be used to move
a message into a specific folder or to delete a message. Messages can also be moved
directly to the trash with a filter. There are two options for creating a new filter: creating
a filter from scratch or creating a filter based on a message to filter. The latter is extremely useful for filtering messages sent to a mailing list.
Setting Up a Filter
Select Tools → Filters. This dialog lists your existing filters, which can be edited or
deleted. Click Add to create a new filter. Alternatively, to create a filter based on a
message, select the message then Tools → Create Filter from Message.
Enter a name for the new filter in Rule Name. Select the criteria to use for the filter.
Options include sender, recipients, source account, subject, date, and status. The dropbox showing Contains provides a variety of options, such as contains, is, and is not.
Select the appropriate condition. Enter the text for which to search. Click Add to add
more filter criteria. Use Execute actions to determine if all or only some of the criteria
must be met to apply the filter.
In the lower part of the window, determine the action to take when the filter criteria are
met. Messages can, for example, be moved or copied to a folder or assigned a special
164
color. When moving or copying, click to select the destination folder. In the folder list
that appears, select the folder. To create a new folder, click New. Click OK when the
correct folder is selected. When finished creating the filter, click OK.
Applying Filters
Filters are applied in the order listed in the dialog accessed with Tools → Filters. Change
the order by highlighting a filter and clicking Up or Down. Click OK to close the filter
dialog when finished.
Filters are applied to all new mail messages. They are not applied to mail already in
your folders. To apply filters to messages already received, select the desired messages
then select Actions → Apply Filters.
11.4
Contacts
Evolution can use several different address books. Available books are listed in the left
frame. Search for a particular contact using the search bar. Add contacts in several
formats to the Evolution address book using File → Import. Right-click a contact to
open a menu in which to select from a variety of options, such as forwarding the contact
or saving it as a vCard. Double-click a contact to edit it.
Evolution: An E-Mail and Calendar Program
165
Figure 11.2
The Evolution Address Book
11.4.1 Adding Contacts
Along with the name and e-mail address, Evolution can store other address and contact
information about a person. Quickly add the e-mail address of a sender by right-clicking
the marked address in the message preview. To enter a completely new contact, click
New Contact in the Contacts view. Both methods open a dialog in which to enter contact
information.
In the Contact tab, enter the contact's name, e-mail addresses, telephone numbers, and
instant messaging identities. Personal Information is for Web addresses and other detailed information. Enter the contact's other address information in Mailing Address.
After entering all desired details for the contact, click OK to add it to the address book.
11.4.2 Making a List
If you frequently send e-mail messages to a group of people, you can simplify the process
by creating a list containing those addresses. Click File → New → Contact List. The
contact list editor opens. Enter a name for the list. Add addresses by typing the address
in the box and clicking Add or by dragging contacts from the Contacts view and dropping
166
them in the box. Toggle Hide addresses to select whether the recipients can see who
else has received the mail. Click OK when finished. The list is now one of your contacts
and appears in the composition window after the first few letters are typed.
11.4.3 Adding Address Books
Configure additional GroupWise and Exchange address books in the account configuration for that account. To add other local or LDAP books, select File → New → Address
Book. In the dialog that opens, select the type of address book and enter the required
information.
11.5
Calendars
Evolution can work with multiple calendars. With File → Import, import calendars in
iCalendar format. Use the calendar to enter appointments and schedule meetings with
others. If desired, set reminders to let you know when your scheduled appointments
are going to start.
Figure 11.3
The Evolution Calendar
Evolution: An E-Mail and Calendar Program
167
11.5.1 Adding Appointments
To add a new appointment to your calendar, click File → New → Appointment. Under
the Appointment tab, enter the details for the appointment. Select a category, if desired,
to ease searching and sorting later. Optionally, use Alarm to set an alarm so Evolution
will remind you before your appointment starts. If the appointment occurs regularly,
set the recurring dates under Recurrence. Click OK after all settings are made. The new
appointment is then shown in your calendar.
11.5.2 Scheduling a Meeting
To schedule a meeting with other people, select File → New → Meeting. Enter information as you would for an appointment. Add the attendees in Invitations or Scheduling.
To enter attendees from your address book, use Contacts to open a list of the contacts
in your address book. Scheduling can also be used to schedule a time that fits all attendees. Press Autopick after configuring participants to automatically find a time.
11.5.3 Adding Calendars
GroupWise and Exchange calendars should be configured in the account configuration.
To add additional local or Web calendars, select File → New → Calendar. Select the
desired type and enter the required information.
11.6
Syncing Data with a Handheld
Evolution is designed so its data can be synced with handheld devices, such as a Palm.
The synchronization uses GNOME Pilot. Select Tools → Pilot Settings to open the
configuration wizard. Refer to the help for more information.
11.7
Evolution for GroupWise Users
GroupWise users should have little trouble using Evolution to access their GroupWise
accounts. Evolution and GroupWise use very similar terminology. Users familiar with
one system should be able to learn the other with minimal effort.
168
11.7.1 Configuring Evolution to Access
Your GroupWise System
Use the Evolution Mail Configuration Assistant to configure Evolution to access your
GroupWise system. To start the Evolution Mail Configuration Assistant, click Preferences → Mail Accounts → Add then click Forward.
On the Identity page, provide your e-mail address in the GroupWise system (for example,
[email protected]), then click Forward.
On the Receiving Email page, select IMAP in Server Type, specify the hostname of
your GroupWise server in Host, set the other settings on the Receiving Options page
as appropriate for your system, then click Forward.
On the Sending Email page, select SMTP in Server Type, specify the hostname of your
GroupWise server in Host, set the other Sending Email options as appropriate for your
system, then click Forward.
On the Account Management page, specify the name you want to use to identify this
account on the Evolution Settings page then click Forward.
Click Apply to create the GroupWise account. Your GroupWise mailbox now appears
in the list of available e-mail accounts.
11.8
For More Information
Evolution offers extensive internal help pages. Use the Help menu to access this information. For more information about Evolution, refer to the project's Web site at
http://www.gnome.org/projects/evolution/.
Evolution: An E-Mail and Calendar Program
169
Kontact: An E-Mail and Calendar
Program
12
Kontact combines the functionality of a number of KDE applications into a convenient,
single interface for personal information management. These applications include KMail
for e-mail, KOrganizer for the calendar, KAddressbook for contacts, and KNotes for
notes. It is also possible to sync data with external devices, such as a PalmPilot or other
handheld device. Kontact integrates easily with the rest of the KDE desktop and connects
to a variety of groupware servers. It includes extra features, such as spam and virus
filtering and an RSS reader.
Start Kontact from the main menu with Office → Kontact (Personal Information
Manager). Alternatively, enter kontact in a command line. You can also open the
individual components instead of the combined application if you only need partial
functionality.
12.1
Importing E-Mail from Other
Mail Programs
To import e-mail from other applications, select Tools → Import Messages from the
mail view in Kontact. It currently features import filters for Outlook Express, the mbox
format, e-mail text format, Pegasus Mail, Opera, Evolution, and more. The import
utility can also be started separately with the command kmailcvt.
Select the corresponding application and confirm with Continue. A file or a folder must
be provided, depending on the selected type. Kontact then completes the process.
Kontact: An E-Mail and Calendar Program
171
12.2
Kontact Overview
The default window view, which shows the Summary, is shown in Figure 12.1, “The
Kontact Window Showing the Summary” (page 172). Use the buttons in the left section
to access the different components.
The Summary provides basic information, including upcoming birthdays and to-dos,
weather, and the status of KPilot. The news section can access RSS feeds to provide
updated news of interest to you. Use Settings → Configure Summary View to configure
the information displayed.
Figure 12.1
The Kontact Window Showing the Summary
12.2.1 Mail
The folder area to the left contains a list of your mail folders (mail boxes) indicating
the total number of messages and how many are still unread. To select a folder, simply
click it. The messages in that folder appear in the top right frame. The number of messages in that folder is also shown in the status bar at the bottom of the application window.
172
The subject, sender, and time of receipt of each message are listed in the header area
to the right. Click a message to select it and display it in the message window. Sort the
messages by clicking one of the column headers (subject, sender, date, etc.). The contents
of the currently selected message are displayed in the message frame of the window.
Attachments are depicted as icons at the end of the message, based on the MIME type
of the attachment, or they can be displayed inline.
Messages can be marked with different status flags. Change the status with Message
→ Mark Message. You can use this feature to assign a status to a message, such as
important or ignored. For example, you can highlight important messages that you do
not want to forget. Display only messages with a certain status using Status in the search
bar.
12.2.2 Contacts
The upper left frame of this component shows all addresses in the currently activated
address books. The lower left frame lists your address books and shows whether each
one is currently active. The right frame shows the currently selected contact. Use the
search bar at the top to find a particular contact.
12.2.3 To-Do List
To-do List shows your list of tasks. Click the field at the top to add a new item to the
list. Right-click in a column of an existing item to make changes to the value in that
column. An item can be broken into several subitems. Right-click and select New Subto-do to create a subitem. You can also assign to-dos to other people.
12.2.4 Calendar
The calendar view is divided into a number of frames. By default, view a small calendar
of this month and a week view of the current week. Also find a list of to-dos, a detailed
view of the current event or to-do, and a list of calendars with the status of each. Select
a different view from the toolbar or the View menu.
Kontact: An E-Mail and Calendar Program
173
12.2.5 Notes
Use the Notes component to keep sticky notes to yourself. If you are using KDE, use
the KNote icon in the system tray to make your notes visible on the desktop.
12.3
Mail
Kontact uses KMail as its e-mail component. To configure it, open the mail component
then select Settings → Configure KMail. KMail is a fully-featured e-mail client that
supports a number of protocols. Tools contains several useful tools for managing unwanted e-mails. Use Find to perform a detailed search for messages. Anti-Spam Wizard
can help manage tools for filtering unwanted commercial e-mails. Anti-Virus Wizard
helps manage e-mail virus scanners. These two wizards work with external spam and
virus software. If the options are disabled, install additional packages for protection
against spam and viruses.
Figure 12.2
174
The Kontact Mail Component
12.3.1 Configuring Accounts
Kontact can manage multiple e-mail accounts, such as your private e-mail address and
your business address. When writing an e-mail, select one of the identities previously
defined by clicking View → Identity. To create a new identity profile, select Settings
→ Configure KMail then Identities → New. In the dialog that opens, give the new
identity a name, such as “private” or “office.” Click OK to open a dialog in which to
enter additional information. You can also assign an identity to a folder so that, when
replying to a message in that folder, the assigned identity is selected.
Under the General tab, enter your name, organization, and e-mail address. Under
Cryptography, select your keys to send digitally signed or encrypted messages. For the
encryption features to work, first create a key with KGpg, described in Chapter 6, Encryption with KGpg (page 101).
Under Advanced, you can enter a reply-to and a blind carbon-copy address, choose a
dictionary, select the folders for drafts and sent messages, and define how messages
should be sent. Under Signature, decide if and how each of your messages should be
signed with an extra block of text at the end. For example. you might sign each e-mail
with your contact information. To activate this option, select Enable Signature and
decide whether to obtain the signature from a file, an input field, or the output of a
command. When you are finished with all your identity settings, confirm with OK.
The settings under Network decide how Kontact receives and sends e-mail. There are
two tabs, one each for sending and for receiving mail. Many of these settings vary depending on the system and network in which your mail server is located. If you are not
sure about the settings or items to select, consult your ISP or system administrator.
To create outgoing mail boxes under the Sending tab, click Add. Choose between the
SMTP and sendmail transport types. SMTP is the correct choice in most cases. After
making this selection, a window appears in which to enter SMTP server data. Provide
a name and enter the server address (as given to you by your ISP). If the server wants
you to authenticate yourself, enable Server requires authentication. Security settings
are under the Security tab. Specify your preferred encryption method here.
Make settings for receiving e-mail under the Receiving tab. Use Add to create a new
account. Choose between different methods for retrieving mail, such as local (stored
in Mbox or Maildir format), POP3, or IMAP. Make the settings appropriate for your
server.
Kontact: An E-Mail and Calendar Program
175
12.3.2 Creating Messages
To compose new messages, select Message → New Message or click the corresponding
icon in the toolbar. To send messages from different e-mail accounts, select one of the
identities as described in Section 12.3.1, “Configuring Accounts” (page 175). In To,
enter an e-mail address or part of a name or address in your address book. If Kontact
can match what you enter to something in the address book, a selection list opens. Click
the desired contact or complete your input if none matches. To select directly from the
address book, click the ... button next to the Address field.
To attach files to your message, click the paperclip icon and select the file to attach.
Alternatively, drag a file from the desktop or another folder to the New Message window
or select one of the options in the Attach menu. Normally, the format of a file is recognized correctly. If the format is not recognized, right-click the icon. From the menu
that appears, select Properties. Set the format and filename in the next dialog and add
a description. In addition, decide whether the attached file should be signed or encrypted.
When you are finished composing your message, send it immediately with Message
→ Send or move it to the outbox with Message → Queue. If you send the e-mail, the
message is copied to sent-mail after having been sent successfully. Messages moved
to the outbox can be edited or deleted.
12.3.3 Encrypted E-Mail and Signatures
To encrypt your e-mail, first generate a key pair as described in Chapter 6, Encryption
with KGpg (page 101). To configure the details of the encryption procedure, select Settings → Configure KMail → Identities to specify the identity under which to send encrypted and signed messages. Then press Modify . After confirming with OK, the key
should be displayed in the corresponding field. Close the configuration dialog with OK.
12.3.4 Folders
Message folders help to organize your messages. By default, they are located in the
directory ~/.kde/share/apps/kmail/mail. When starting KMail for the first
time, the program creates several folders. inbox is where new messages fetched from
a server are initially placed. outbox is used for temporary storage of messages queued
for sending. sent-mail is for copies of messages sent. trash contains copies of all
176
e-mails deleted with Del or Edit → Delete. drafts is where you can save unfinished
messages. If you are using IMAP, the IMAP folders are listed below the local folders.
Each incoming mail server, for example local or IMAP, has its folders in the Folder
list.
If you want to organize your messages in additional folders, create new folders by selecting Folder → New Folder. This opens a window in which to specify the name and
format of the new folder.
Right-click the folder for a context menu offering several folder operations. Click Expire
to specify the expiration date for read and unread messages, what should happen with
them after expiration, and whether expired messages should be deleted or moved to a
folder. If you intend to use the folder to store messages from a mailing list, set the
necessary options under Folder → Mailing List Management.
To move one or several messages from one folder to another, highlight the messages
to move then press M or select Message → Move to. In the list of folders that appears,
select the folder to which to move your messages. Messages can also be moved by
dragging them from the upper window and dropping them into the appropriate folder
in the left window.
12.3.5 Filters
Filters are a convenient method of automatically processing incoming mail. They use
aspects of the mail, such as sender or size, to move mail to certain folders, delete unwanted mails, bounce mails back to the sender, or perform a number of other actions.
Setting Up a Filter
To create a filter from scratch, select Settings → Configure Filters. To create a filter
based on an existing message, select the desired message in the Header list, then select
Tools → Create Filter and the desired filter criteria.
Select the match method for filter criteria (all or any). Then select criteria that applies
only to the desired messages. In Filter Actions, set what the filter should do to the
messages that meet the criteria. Advanced Options provides control over when the filter
is applied and whether additional filters should be considered for these messages.
Kontact: An E-Mail and Calendar Program
177
Applying Filters
Filters are applied in the order listed in the dialog accessed with Settings → Configure
Filters. Change the order by selecting a filter and clicking the arrow buttons. Filters
are only applied to new incoming messages or sent messages as specified in the filter's
advanced options. To apply filters to existing messages, select the desired messages
then Message → Apply Filters.
If your filters do not act as expected, monitor them with Tools → Filter Log Viewer.
When logging is enabled in this dialog, it shows how messages are processed by your
filters and can help locate the problem.
12.4
Contacts
The contacts component uses KAddressBook. Configure it with Settings → Configure
KAddressBook. To search for a particular contact, use the search bar. With Filter, select
to display only contacts in a certain category. Right-click a contact to open a menu in
which to select from a variety of options, such as sending the contact information in an
e-mail.
Figure 12.3
178
The Kontact Address Book
12.4.1 Adding Contacts
To add a contact with the name and e-mail address from an e-mail, right-click the address
in the mail component and select Open in Address Book. To add a new contact without
using an e-mail, select File → New Contact in the address component. Both methods
open a dialog in which to enter information about the contact.
In the General tab, enter basic contact information, such as name, e-mail addresses,
and telephone numbers. Categories can be used to sort addresses. Details contains more
specific information, such as birthday and spouse's name.
If your contact uses an instant messenger, you can add these identities in IM Addresses.
If you do this and have Kopete or another KDE chat program running at the same time
as Kontact, view status information about these identities in Kontact. In Crypto Settings,
enter the contact's encryption data, such as public key.
Misc has additional information, such as a photograph and the location of the user's
Free/Busy information. Use Custom Fields to add your own information to the contact
or address book.
Contacts can also be imported in a variety of formats. Use File → Import and select
the desired format. Then select the file to import.
12.4.2 Making a Distribution List
If you frequently send e-mail messages to the same group of people, a distribution list
enables you to store multiple e-mail addresses as a single contact item so that you do
not have to enter each name individually in every e-mail you send to that group. First,
click Settings → Show Extension Bar → Distribution List Editor. In the new section
that appears, click New List. Enter a name for the list then click OK. Add contacts to
the list by dragging them from the address list and dropping them in the distribution
list window. Use this list like you would an individual contact when creating an e-mail.
Kontact: An E-Mail and Calendar Program
179
12.4.3 Adding Address Books
IMPORTANT: Groupware Address Books
The best way to add groupware resources is with the Groupware Wizard, a
separate tool. To use it, close Kontact then run groupwarewizard in a
command line or from the Office group of the KDE menu. Select the server
type, such as SLOX, GroupWise, or Exchange, from the list offered then enter
the address and authentication data. The wizard then adds the available resources to Kontact.
Kontact can access multiple address books, such as shared ones offered by Novell
GroupWise or an LDAP server. Select Settings → Show Extension Bar → Address
Books to view the current address books. Press Add to add one then select the type and
enter the required information.
The check boxes in front of the books show the activation status of each address book.
To prevent the display of a book without deleting it, uncheck it. Remove deletes the
selected book from the list.
12.5
Calendar
Kontact uses KOrganizer as its calendar component. To configure it, use Settings →
Configure KOrganizer. With the calendar, enter appointments and schedule meetings
with others. If desired, you can be reminded of upcoming events. You can also import,
export, and archive calendars with the options in File.
180
Figure 12.4
The Kontact Calendar
12.5.1 Scheduling an Event
Add a new event or meeting with Actions → New Event. Enter the desired details. Under
Reminder, specify the exact time (minutes, hours, or days in advance) when the attendees
should be reminded of the event. If an event recurs, specify the appropriate interval.
Another way to create an event at a specific point in the calendar is to double-click the
corresponding field in one of the program's calendar views. This opens the same dialog
window as that available from the menu. Alternatively, select a time range in the Calendar view and right-click.
Specify the attendees of an event by entering their data manually in the dialog or by
inserting data from the address book. To enter data manually, select New. To import
data from the address book, click Select Addressee then select the corresponding entries
from the dialog. To schedule the event based on the participants' availability, go to
Free/Busy and click Pick Date.
Use the Recurrence tab to configure an event that happens on a regular basis. Attachments can be convenient for linking other information with the event, such as an agenda
for a meeting.
Kontact: An E-Mail and Calendar Program
181
12.5.2 Adding Calendars
IMPORTANT: Groupware Calendars
The best way to add groupware resources is with Groupware Wizard, a separate
tool. To use it, close Kontact then run groupwarewizard in a command line
or from the Office group of the KDE menu. Select the server type, such as
SLOX, GroupWise, or Exchange, from the list offered then enter the address
and authentication data. The wizard adds the available resources to Kontact.
The calendar module can connect to multiple calendars simultaneously. This is useful,
for example, to combine a personal calendar with an organizational one. To add a new
calendar, click Add then select the calendar type. Complete the necessary fields.
The check boxes in front of the calendars show the activation status of each. To prevent
the display of a calendar without deleting it, uncheck it. Remove deletes the selected
calendar from the list.
12.6
Syncing Data with a Handheld
Kontact is designed so its data can be synced with handheld devices, such as a Palm.
View information about the status of KPilot in the summary. Refer to Chapter 13,
Synchronizing a Handheld Computer with KPilot (page 185) for information about
configuring and using KPilot.
12.7
Kontact for GroupWise Users
If you are used to working in GroupWise, you should have very little trouble adjusting
to Kontact. The two programs share many concepts and provide many of the same
services. This section discusses notable terminology differences, as well as some tips
to help GroupWise users make the most of Kontact.
182
12.7.1 Terminology Differences
The following table lists some key terminology differences between Kontact and
GroupWise.
Table 12.1
Kontact and GroupWise Terminology Differences
GroupWise
Kontact
Appointments
Events
Busy search
Free/Busy
Notes
Journal entries
Posted, nonposted items
An event without attendees is posted. If an
event has attendees, it is a Sent item.
Tasks
To-dos
12.7.2 Tips for GroupWise Users
This section contains hints to help GroupWise users work with some of the differences
between GroupWise and Kontact.
Contact Information
You can add your GroupWise Messenger and e-mail contacts to your Kontact contact
information. Then you can create an e-mail or open an instant messaging session with
that contact by right-clicking the name in the Contact view.
Color Coding
It is helpful to color code GroupWise items, as well as items from other sources. Color
coding makes it easy to scan your e-mails, contacts, and other information for items
from a particular source.
Kontact: An E-Mail and Calendar Program
183
Inviting Attendees to Events
Unlike GroupWise, Kontact does not automatically enter you as an attendee for events
you schedule. Make sure that you remember to invite yourself.
12.8
For More Information
Kontact includes help for itself and its various components. Access it with Help →
Kontact Handbook. The project's Web page, http://www.kontact.org, is also
informative.
184
Synchronizing a Handheld
Computer with KPilot
13
Handheld computers are in widespread use among users who need to have their
schedules, to-do lists, and notes with them everywhere they go. Often users want the
same data to be available both on the desktop and on the portable device. This is where
KPilot comes in—it is a tool to synchronize data on a handheld with that used by the
KDE applications KAddressBook, KOrganizer, and KNotes, which are part of Kontact.
The main purpose of KPilot is to allow sharing of data between the applications of a
handheld computer and their KDE counterparts. KPilot does come with its own builtin memo viewer, address viewer, and file installer, but these cannot be used outside the
KPilot environment. Independent KDE applications are available for all these functions
except the file installer.
For communication between the handheld and the different desktop programs, KPilot
relies on conduits. KPilot itself is the program that oversees any data exchange between
the two computer devices. Using a particular function of the handheld on your desktop
computer requires that the corresponding conduit is enabled and configured. For the
most part, these conduits are designed to interact with specific KDE programs, so in
general they cannot be used with other desktop applications.
The time synchronization conduit is special in that there is no user-visible program for
it. It is activated in the background with each sync operation, but should only be enabled
on computers that use a network time server to correct their own time drift.
When a synchronization is started, the conduits are activated one after another to carry
out the data transfer. There are two different sync methods: a HotSync operation only
synchronizes the data for which any conduits have been enabled while a backup operation
performs a full backup of all data stored on the handheld.
Synchronizing a Handheld Computer with KPilot
185
Some conduits open a file during a sync operation, which means the corresponding
program should not be running at the given time. Specifically, KOrganizer should not
be running during a sync operation.
13.1
Conduits Used by KPilot
The conduits used by KPilot can be enabled and configured after selecting Settings →
Configure KPilot. The following is a list of some important conduits:
Address Book
This conduit handles the data exchange with the handheld's address book. The KDE
counterpart for managing these contacts is KAddressBook. Start it from the main
menu or with the command kaddressbook.
KNotes/Memos
This conduit allows you to transfer notes created with KNotes to the handheld's
memo application. Start the KDE application from the main menu or with the
command knotes.
Calendar (KOrganizer)
This conduit is responsible for syncing the appointments (events) of the hendheld.
The desktop equivalent is KOrganizer.
ToDos (KOrganizer)
This conduit is responsible for syncing to-do items. The desktop counterpart is
KOrganizer.
Time Synchronization Conduit
Enabling this conduit adjusts the handheld's clock to that of the desktop computer
during each sync operation. This is only a good idea if the clock of the desktop
computer itself is corrected by a time server at fairly frequent intervals.
186
Figure 13.1
13.2
Configuration Dialog with the Available Conduits
Configuring the Handheld
Connection
To be able to use KPilot, first set up the connection with the handheld computer. The
configuration depends on the type of cradle (docking unit) used with the handheld.
There are two types of these: USB cradles or cables and serial cradles or cables.
13.2.1 Configuring the Connection from
within KPilot
The easiest way to set up the connection is by using the configuration assistant. Select
Settings → Configuration Assistant to start the assistant. In the first step, enter your
username and the name of the device to which the handheld is connected. The assistant
attempts to detect them itself if you select Autodetect Handheld & Username. If the
autodetection fails, refer to Section 13.2.2, “Creating a /dev/pilot Link” (page 188).
After confirming with Next, the assistant prompts you to specify the applications that
should be used for synchronization. You can choose among the KDE application suite
(default), Evolution, and none. After selecting, close the window with Finish.
Synchronizing a Handheld Computer with KPilot
187
13.2.2 Creating a /dev/pilot Link
The setup of the connection with a serial handheld cradle is different from that of a
USB cradle. Depending on which cradle is used, you may or may not need to create a
symbolic link named /dev/pilot.
USB
Normally, a USB cradle is autodetected and there should be no need to create the
symbolic link mentioned.
Serial
With a serial cradle, you need to know to which serial port it is actually connected.
Serial devices are named /dev/ttyS?, starting from /dev/ttyS0 for the first
port. To set up a cradle connected to the first serial port, enter the command:
ln -s /dev/ttyS0 /dev/pilot
13.3
Configuring the KAddressBook
Conduit
Initially, it should be sufficient to enable the KAddressBook conduit without changing
any of the defaults. After the data has been synchronized for the first time, configure
the details: what to do in case of conflicts, the way in which backup databases are saved,
and how certain fields as stored on the handheld should be assigned to the fields expected
by KAddressBook.
13.4
Managing To-Do Items and
Events
On the KDE desktop, to-dos (tasks) and events (appointments) are managed with KOrganizer. Start the application from the main menu, with the command korganizer,
or as part of Kontact. After enabling the calendar and the to-do conduit of KPilot, set
some configuration options before using them.
188
Figure 13.2
KPilot Configuration
KOrganizer stores its files in the directory ~/.kde/share/apps/korganizer.
However, given that the directory .kde/ begins with a dot, it may not be shown by
the file selection dialog. In this case, enter the complete path manually or explicitly
toggle the display of hidden files (dot files) in the file selection dialog. The default
shortcut for this is F8 .
After opening the directory ~/.kde/share/apps/korganizer, select a file that
can be used as a calendar file by KOrganizer. In this example, this is the file palm
.ics. In the case of a user called tux, the complete path and filename would be
/home/tux/.kde/share/apps/korganizer/palm.ics, as shown in Figure 13.3, “Dialog Showing the Path to a KOrganizer Calendar File” (page 189).
Figure 13.3
Dialog Showing the Path to a KOrganizer Calendar File
Synchronizing a Handheld Computer with KPilot
189
KOrganizer should not be running when data is being exchanged with the handheld.
Otherwise KPilot fails to carry out the sync operation.
13.5
Working with KPilot
Synchronizing the data of KDE applications with those of the handheld computer is
quite easy. Simply start KPilot then press the HotSync button on the cradle or cable to
initiate the sync operation.
Figure 13.4
The Main Window of KPilot
13.5.1 Backing Up Data from the Handheld
To do a full backup, select File → Backup. The backup is performed during the next
sync operation. After that, switch back by selecting File → HotSync from the menu.
Otherwise, the time-consuming full backup will be performed again during the next
sync operation.
After a full backup, all copies of the handheld's programs and databases are found in
~/.kde/share/apps/kpilot/DBBackup/USERNAME, where USERNAME is
the name of the user registered on the handheld.
190
The two built-in KPilot viewers can be used for a quick lookup of addresses or memos,
but they are not designed to actually manage this data. The KDE applications mentioned
above are much more suited for these tasks.
13.5.2 Installing Programs on the Handheld
The File Installer module is an interesting and useful tool for the installation of handheld
programs. These programs normally have the extension .prc and they are ready to
start immediately after uploading them to the handheld. Before using such add-on programs, read their licenses as well as the instructions included.
13.5.3 Synchronizing Your Address Books
and Calendars
To synchronize your calendars and addresses, use the KDE tools MultiSynK. Start the
tool with the command multisynk. Create a Konnector pair before you synchronize
your data. Go to File → New and select your Konnectors. Leave it with Ok.
The name is listed in the main window. To synchronize with your handheld computer
go to File → Sync.
Synchronizing a Handheld Computer with KPilot
191
14
Using Beagle
Beagle is a search tool that indexes your personal information space to help you find
whatever you are looking for. You can use Beagle to find documents, e-mails, Web
history, Instant Messenger and ITC conversations, source code, images, music files,
applications, and much more.
Beagle supports the following data sources:
• File system
• Application launchers
• Evolution mail and address book
• Gaim instant messaging logs
• Firefox Web pages (as you view them)
• Blam and Liferea RSS aggregators
• Tomboy notes
It also supports the following file formats:
• OpenOffice.org
• Microsoft Office (doc, ppt, xls)
• HTML
Using Beagle
193
• PDF
• Images (jpeg, png)
• Audio (mp3, ogg, flac)
• AbiWord
• Rich Text Format (rtf)
• Texinfo
• Man pages
• Source code (C, C++, C#, Fortran, Java, JavaScript, Pascal, Perl, PHP, Python)
• Plain text
Beagle automatically indexes everything in your home directory, but you can choose
to exclude certain files or directories. Beagle also includes a variety of tools that you
can use to search your data.
14.1
Indexing Data
The Beagle daemon (beagled) automatically performs all indexing. By default, everything in your home directory is indexed. Beagle detects changes made to your home
directory and reindexes the data accordingly.
• Files are immediately indexed when they are created, are reindexed when they are
modified, and are dropped from the index when they are deleted.
• E-mails are indexed upon arrival.
• IM conversations are indexed as you chat, one line at a time.
Indexing your data requires a fair amount of computing power, but the Beagle daemon
tries to be as unobtrusive as possible. It contains a scheduler that works to prioritize
tasks and control CPU usage, based on whether you are actively using your workstation.
194
14.1.1 Preventing Files and Directories
from Being Indexed
If you want to prevent a directory (and all of its subdirectories) from being indexed,
create an empty file named .noindex and place it in the directory. You can add a list
of files and directories to the .noindex file to prevent those files and directories from
being indexed. Wild cards are permitted in the .noindex file.
You can also put a .neverindex file in your home directory with a list of files that
should never be indexed. Wild cards are also allowed in this file. Use the same wild
cards as you use for glob (for example, f*le??.txt). You can also use more
powerful regular expressions by adding a forward slash both before and after your
pattern (for example, /file.*.txt/). For more information, see the glob-UNIX
Web site (http://docs.python.org/lib/module-glob.html).
14.1.2 Indexing Manually
Beagle has an effective system for determining when to index your files and it tries to
not interfere with other applications you might be running. It intentionally times its indexing based on load and whether your system is idle, so as not to adversely affect your
desktop experience. However, if you want to index your home directory right away,
enter the following command in a terminal window before running Beagle:
export BEAGLE_EXERCISE_THE_DOG=1
14.1.3 Checking the Status of Your Index
Beagle includes the following commands to let you see the current indexing status:
beagle-index-info
Displays how many documents have been indexed and what type of documents
have been indexed.
beagle-status
Displays the current work the Beagle daemon is doing (on an ongoing basis).
Using Beagle
195
14.2
Searching Data
Beagle offers the following tools that let you search through the data that you have indexed.
14.2.1 Best
Best (Bleeding Edge Search Tool) is a graphical tool that searches through your indexed
information. Best does not query the index directly; it passes the search terms to the
Beagle daemon, which sends any matches back to Best. Best then renders the results
and allows you to perform actions on the matching objects.
To open Best in KDE, click K Menu → System → File System → Beagle Search. In
GNOME, click Applications → System → File System → Beagle Search.
Figure 14.1
196
Beagle Search
To use Best, simply type your search text in the entry box at the top then press
or click Find. Best queries your indexed files and returns the results.
Enter
You can use the results list to open a file, mail a file, send an instant message, replay
to a file, forward a file, or display a file in your file manager. The options available for
each file depend on its type.
You can also use Anywhere to limit your search to files in a specific location, such as
your address book or Web pages, or to display only a specific type of file in your results
list.
14.2.2 beagle-query
Beagle has a command line tool you can use to search your Beagle index. To use this
tool, enter the following command in a terminal window:
beagle-querysearch
Replace search with the text to find and the beagle-query tool returns results. You
can use wild cards with this command.
Use beagle-query --verbose search to display detailed information about
the search results.
Using Beagle
197
Part V Graphics
Digital Cameras and Linux
15
Managing photos from your camera can be fun if you have the right tools. Linux offers
several handy utilities for sorting and organizing your photographs. These include
gphoto2, Konqueror, Digikam, and f-spot.
A comprehensive list of supported cameras is available at http://www.gphoto
.org/proj/libgphoto2/support.php. If gphoto2 is installed, retrieve the
list with the command gphoto2 --list-cameras. Get information about the
available commands with gphoto2 --help.
TIP: Unsupported Cameras
If you do not find your camera in the list from gphoto, do not despair. It is
very likely that your camera is supported as a USB mass storage device. Find
more information in Section 15.2, “Accessing the Camera” (page 202).
15.1
Connecting to the Camera
The fastest and most convenient way to connect digital cameras to the computer is USB,
provided the kernel, the camera, and the computer support it. The standard SUSE kernel
provides this support. A suitable cable is also required.
Simply connect the camera to the USB port and turn on the camera. You may need to
switch your camera to a special data transfer mode. For this procedure, consult the
manual of your digital camera.
Digital Cameras and Linux
201
15.2
Accessing the Camera
There are three possibilities for accessing the pictures on the camera. It depends on
your camera and which protocol it supports. Usually it is USB mass storage, which is
handled by the hotplug system, or PTP (also known as PictBridge). Some camera
models do not work with either protocol. To support these, gphoto2 includes specific
drivers.
It is easiest if your camera supports USB mass storage. Read the documentation of your
camera if you are unsure if this is possible. Some support two protocols, like both PTP
and USB mass storage. Unfortunately, there are also some that communicate with a
proprietary protocol, which can complicate the tasks. If your camera does not support
USB mass storage or PTP, the following descriptions will not work. Try gphoto2
--list-cameras and the information at http://www.gphoto.org/.
If your camera can be switched to a USB mass storage device, select this option. After
you connect it with the USB port of your computer and turn it on, it is detected by the
hotplug system. This takes care of mounting the device automatically, so it is easily
accessible. The KDE desktop shows a camera icon after a successful mount.
After the camera is successfully mounted, see a new directory under /media, beginning
with usb and lots of numbers. Each vendor and product has a number, so when you
connect a device on your computer it has always the same name. Depending on what
you have connected to the USB bus, find different entries. The only problem left is to
find the correct entry for your camera. Try to list one of these directories (DCIM/xxx)
and see what happens. Each camera has a different tree structure, so there is no general
rule. If you can see JPEG files in a directory, you probably found it.
After you find your correct directory, you can copy, move, or delete the files from your
camera with a file manager, such as Konqueror, or simple shell commands (see Section 27.3, “Important Linux Commands” (page 393) and the Reference).
15.3
Using Konqueror
KDE users can easily access digital cameras by means of the familiar Konqueror interface. Connect your camera to the USB port. A camera icon should appear on the desktop.
Click this icon to open the camera in Konqueror. The camera can also be accessed by
entering the URL camera:/ in Konqueror. Navigate through the camera's directory
202
structure until the files are shown. Use the usual Konqueror file management features
to copy the files as desired. More information about using Konqueror is available in
Chapter 3, The Web Browser Konqueror (page 73).
15.4
Using Digikam
Digikam is a KDE program for downloading photographs from digital cameras. The
first time it is run, Digikam asks where to store your photo album. If you enter a directory that already contains a collection of photographs, Digikam treats each subfolder
as an album.
On start-up, Digikam presents a window with two sections: your albums are displayed
to the left and the photographs of the current album are displayed to the right. See Figure 15.1, “The Main Window of Digikam” (page 203).
Figure 15.1
The Main Window of Digikam
15.4.1 Configuring Your Camera
To set up a camera in Digikam, select Camera → Add Camera. First, try to autodetect
the camera with Auto-Detect. If this fails, browse the list for your model with Add. If
Digital Cameras and Linux
203
your camera model is not included in the list, try an older model or use USB/IEEE mass
storage camera. Confirm with Ok.
15.4.2 Downloading Pictures from Your
Camera
After your camera has been configured correctly, connect to your camera with the
Camera menu and the name that you gave in the dialog from Section 15.4.1, “Configuring Your Camera” (page 203). Digikam opens a window and begins to download
thumbnails and displays them as in Figure 15.2, “Downloading Pictures from Camera”
(page 204). Right-click an image to open a pop-up menu with the options to View, display
some Properties or EXIF Information, Download, or Delete the image. With Advanced,
select renaming options and how the camera-provided information (EXIF) should be
handled.
Figure 15.2
Downloading Pictures from Camera
The renaming options can be very convenient if your camera does not use meaningful
filenames. You can let Digikam rename your photographs automatically. Give a unique
prefix and, optionally, a date, time, or sequence number. The rest is done by Digikam.
Select all photographs to download from the camera by pressing the left mouse button
or clicking individual photographs with Ctrl pressed. Selected photographs appear with
inverted colors. Click Download. Select the destination from the list or by creating a
new album with New Album. This automatically suggests a filename with the current
date. Confirm with Ok to start the download process.
204
15.4.3 Getting Information
Getting information about the photograph is not difficult. A short summary is displayed
as a tool tip if you point with the mouse cursor at the thumbnail. For longer information,
right-click the photograph and choose Properties from the menu. A dialog box opens
with three tabs, General, EXIF, and Histogram.
General lists the name, type, owner, and some other basic information. The more interesting part is the EXIF tab. The camera stores some metadata for each photograph.
Digikam reads these properties and displays them in this list. Find the exposure time,
pixel dimensions, and others. To get more information for the selected list entry, press
Shift + F1 . This shows a small tool tip. The last tab, Histogram, shows some statistical
information.
15.4.4 Managing Albums
Digikam inserts a My Albums folder by default, which collects all your photographs.
You can store these into subfolders later. The albums can be sorted by their directory
layout, by the collection name that has been set in the album properties or by the date
that the albums were first created (this date can also be changed in the properties of
each album).
To create a new album, you have some possibilities:
• Uploading new photographs from the camera
• Creating a new album by clicking the New Album button in the toolbar
• Importing an existing folder of photographs from your hard disk (select Album →
Import → Import Folders)
• Right-clicking My Albums and selecting New Album
After selecting to create an album in your preferred way, a dialog box appears. Give
your album a title. Optionally, choose a collection, insert some comments, and select
an album date. The collection is a way of organizing your albums by a common label.
This label is used when you select View → Sort Albums → By Collection. The comment
is shown in the banner at the top of the main window. The album date is used when
you select View → Albums → By Date.
Digital Cameras and Linux
205
Digikam uses the first photograph in the album as the preview icon in the My Albums
list. To select a different one, right-click the respective photograph and select Set as
Album Thumbnail from the context menu.
15.4.5 Managing Tags
Managing lots of different photographs with different albums can sometimes be complex.
To organize individual photographs, Digikam provides the My Tag system.
For example, you have photographed your friend John at different times and you want
to collect all images, independent of your album. This let you find all photographs very
easily. First, create a new tag by clicking My Tags → People. From the context menu,
choose New Tag. In the dialog box that appears, enter John as title and optionally set
an icon. Confirm with Ok.
After creating your tag, assign it to the desired pictures. Go to each album and select
the respective photographs. Right-click and choose Assign Tag → People → John from
the menu that appears. Alternativly, drag the photographs to the tag name under My
Tags and drop them there. Repeat as necessary with other albums. View all the images
by clicking My Tags → People → John. You can assign more than one tag to each
photograph.
Editing tags and comments can be tedious. To simplify this task, right-click a photograph
and select Edit Comments & Tags. This opens a dialog box with a preview, a comment
field, and a tag list. Now you can insert all the needed tags and add a comment. With
Forward and Back, navigate in your album. Store your changes with Apply and leave
with Ok.
15.4.6 Exporting Image Collections
Digikam provides several export options that help you archive and publish your personal
image collections. It offers archiving to CD or DVD (via k3b), HTML export, and export
to a remote gallery.
To save your image collection to CD or DVD, proceed as follows:
1 Select File → Export → Archive to CD/DVD.
206
2 Make your adjustments in the Create CD/DVD Archive dialog using its various
submenus. After that, click OK to initiate the burning process.
a Selection: Determine which part of your collection should be archived by
selecting albums and tags.
b HTML Interface: Decide whether your image collection should be accessible
via an HTML interface and whether autorun functionality should be added
to your CD/DVD archive. Set a selection title and image, font, and background properties.
c Media Volume Descriptor: Change the settings for volume description, if
necessary.
d Media Burning: Adjust the burning options to your needs, if necessary.
To create an HTML export of your image collection, proceed as follows:
1 Select File → Export → HTML Export.
2 Adjust the settings in Create Image Galleries to your needs, using the various
submenus. When you are done, click OK to initiate the gallery creation.
a Selection: Determine which part of your collection should be archived by
selecting albums and tags.
b Look: Set the title and appearance of your HTML gallery.
c Album: Determine the location of the gallery on disk as well as image size,
compression, format, and the amount of metadata displayed in the resulting
gallery.
d Thumbnails: As with the target images, specify size, compression and file
type for the thumbnails used for gallery navitation.
To export your collection to an external image gallery on the Internet, proceed as
follows:
1 Get an account for an external web site holding your gallery.
Digital Cameras and Linux
207
2 Select File → Export → Export to Remote Gallery and provide URL, username,
and password for the external site when asked for them.
Digikam establishes a connection to the site specified and opens a new window
called Gallery Export.
3 Determine the location of your new album inside the gallery.
4 Click New Album and provide the information requested by Digikam.
5 Upload the images to the new album with Add Photos.
15.4.7 Useful Tools
Digikam provides several tools to simplify some tasks. Find them in the Tools menu.
The following is a small selection of the available tools.
Creating a Calendar
If you want to please someone, a custom calendar can be a nice gift. Go to Tools →
Create Calendar, which opens a wizard dialog like that in Figure 15.3, “Creating a
Template for a Calendar” (page 209).
Customize the settings (paper size, image position, font, etc.) and confirm with Next.
Now you can enter the year and select the images to use. After clicking Next again, see
a summary. The final Next opens the KDE Printer dialog. Here, decide if you want to
see a preview, save as PDF, or just print directly.
208
Figure 15.3
Creating a Template for a Calendar
Finding Duplicate Photographs
Sometimes you photograph similar scenes repeatedly and want to keep only the best
shots. This is the perfect task for the Find Duplicate plug-in.
Go to Tools → Find Duplicate Images. Select the albums or tags to handle. Under
Method & Cache, choose the search method: a more accurate or a faster method. After
you confirm with Ok, Digikam proceeds with the investigation.
If it finds some duplicates, it shows the result in a window like Figure 15.4, “Results
of Find” (page 210). Decide which images to delete by activating the desired check
boxes then clicking Delete. Leave the window with Close.
Digital Cameras and Linux
209
Figure 15.4
Results of Find
Batch Processes
Digikam also provides some batch processes that perform a specific task on lots of files.
This can be renaming, converting, resizing, and much more. Find them under Tools →
Batch Processes.
15.4.8 Basic Image Viewing and Editing
with Digikam
Digikam includes its own lean image viewing and editing program. It automatically
opens if you double-click an image's thumbnail.
Use this tool to do some basic image editing on the images you just downloaded from
your camera. You can crop, rotate or flip the image, do some basic color adjustments,
210
apply various colored filters (for example, to export a colored image to black and white),
and efficiently reduce red eyes in portrait shots.
The most important menus are:
Image
Use Edit Comments & Tags to enter comments to a particular image and to assign
a tag (category) to this image. Properties takes you to a window consisting of three
tabs providing general information, EXIF information, and the histogram of this
image.
Fix
This menu contains some of the editing functions most needed in digital photography.
Colors takes you to a submenu where you can modify all basic color settings. You
can also blur or sharpen either the entire picture or just a part of the image you selected. To reduce red eyes in a portrait shot, roughly select the eye region of the
face by just clicking and holding the left mouse pointer and gradually expanding
the selection, select Red Eye Reduction and choose either mild or aggressive reduction depending on whether you selected a whole region or just the eyes.
Transform
The Transform menu offers the crop, rotate, flip, and resize functions. You can also
use the Aspect Ratio Crop option to produce crops in a fixed aspect ratio.
Filters
If you need to transform your color shots into black and white or want to achieve
an aged look in your photographs, check out the Filters menu and choose from the
various export options.
A more detailed description of this tool can be found in Digikam's online help in digiKam
Image Editor, which can be reached with the Help button in Digikam's menu bar.
TIP: Advanced Image Processing
Professional image editing can be done with the GIMP. More information about
The GIMP can be found in Chapter 17, Manipulating Graphics with The GIMP
(page 225).
Digital Cameras and Linux
211
15.5
Using f-spot
f-spot is a managment tool for your collection of digital images tailored for the GNOME
desktop. It allows you to assign different tags to your images in order to categorize
them and offers various neat image editing options.
The first time you run f-spot, tell it where to find the images to import to your f-spot
collection. If you already have a collection of images stored on your hard drive, enter
the path to the respective directory and optionally include subfolders. f-spot imports
these images into its database.
TIP: Tagging Images on Import
If all the images you are importing belong to the same category, you can attach
the appropriate tag on import. Select Attach Tag and choose the matching tag
from the drop down menu.
Figure 15.5
Importing Images to f-spot
f-spot's main window is divided into three main areas. Categories, tags, and detailed
information for the selected images are displayed in a sidebar to the left and a thumbnails
of all images bearing the selected tag or category or, if none is selected, the entire collection is displayed in the right part of the window.
212
Figure 15.6
f-spot's Main Window
A menu bar right at the top of the window allows you to access the main menus. A
toolbar below offers several different functions depicted by a matching icon:
Rotate (Left or Right)
Use this shortcut to change an image's orientation.
Browse
The Browse mode allows you to view and search you entire collection or tagged
subsets of it. You can also use the time line to search images by creation date.
Edit Image
This mode allows you to select one image and do some basic image processing.
Details are available in Section 15.5.6, “Basic Image Processing with f-spot”
(page 217).
Fullscreen
Switch to fullscreen display mode.
Slideshow
Start a slide show.
Digital Cameras and Linux
213
15.5.1 Downloading Pictures From Your
Camera
Import new images from your digital camera connected to the USB port of your computer using File → Import from Camera. The type of camera is detected automatically.
Figure 15.7
Import from Camera
f-spot launches a preview window displaying all the images that are available for
download from camera. The files are copied to the target directory specified via Copy
Files to. If Import files after copy is selected, all images copied from camera are automatically imported to f-spot's database. Tagging can be done on import, if you select
the appropriate tag with Select Tags. If you do not want to import all images on your
camera to your database, just deselect the unwanted one in the preview window.
214
15.5.2 Getting Information
Once you select an image, some basic statistical information on this image is displayed
in the lower left part of the window. This includes the filename, its version (copy or
original image), the date of creation, its size and the exposure which was used in creating
this particular image. View the EXIF data associated with the image file with View →
EXIF Data.
15.5.3 Managing Tags
Use tags to categorize any of your images to create manageable subsets of your collection. If, for example, you would like to get some sort of order in your collection of
portrait shots of your loved ones, proceed like this:
1 Select the Browse mode of f-spot.
2 In the left frame of the f-spot window, select the People category, right-click it,
then choose Create New Tag. The new tags then appear as subcategories below
the People category:
a Create a new tag called Friends.
b Create a new tag called Family.
3 Now attach tags to images or groups of selected images. Right-click an image,
choose Attach Tag, and select the appropriate tag for this image. To attach a tag
to a group of images, click the first one then press Shift and select the other ones
without releasing the Shift key. Right-click for the tag menu and select the
matching category.
After the images have been categorized, you can browse your collection by tag. Just
check People → Family and the displayed collection is limited to the images tagged
Family. Searching your collection by tag is also possible through Find → Find by
Tag. The result of your search is displayed in the thumbnail overview window.
Removing tags from single images or groups of images works similarly to attaching
them. The tag editing functions are also accessible via the Tags menu in the top menu
bar.
Digital Cameras and Linux
215
15.5.4 Search and Find
As mentioned in Section 15.5.3, “Managing Tags” (page 215), tags can be used as a
means to find certain images. Another way, which is quite unique to f-spot, is to use
the Timeline below the toolbar. By dragging the little frame along this time line, limit
the images displayed in the thumbnail overview to those taken in the selected time
frame. f-spot starts with a sensibly chosen default time line, but you can always edit
the time span by moving the sliders to the right and left ends of the time line.
15.5.5 Exporting Image Collections
f-spot offers a range of different export functions for your collections under File →
Export. Probably the most often used of these are Export to Web Gallery and Export
to CD.
To export a selection of images to a web gallery, proceed as follows:
1 Select the images to export.
2 Click File → Export → Export to Web Gallery and select a gallery to which to
export your images or add a new one. f-spot establishes a connection to the Web
location entered for your web gallery. Select the album to which to export the
images and decide whether to scale the images automatically and export titles
and comments.
Figure 15.8
216
Exporting Images to a Web Gallery
To export a selection of images to CD, proceed as follows:
1 Select the images to export.
2 Click File → Export → Export to CD and click OK.
f-spot copies the files and opens the CD writing dialog. Assign a name to your
image disk and determine the writing speed. Click Write to start the CD writing
process.
Figure 15.9
Exporting Images to CD
15.5.6 Basic Image Processing with f-spot
f-spot offers several very basic image editing functionalities. Enter the edit mode of fspot by clicking the Edit Image icon in the toolbar or by double-clicking the image to
edit. Switch images using the arrow keys at the bottom right. Choose from the following
edit functions:
Sharpen
Access this function with Edit → Sharpen. Adjust the values for Amount, Radius,
and Threshold to your needs and click OK.
Digital Cameras and Linux
217
Crop Image
To crop the image to a selection you made, either choose a fixed ratio crop or the
No Constraint option from the drop-down menu at the bottom left, select the region
to crop, and click the scissor icon next to the ratio menu.
Red Eye Reduction
In a portrait shot, select the eye region of the face and click the red eye icon.
Adjust Color
View the histogram used in the creation of the shot and correct exposure and color
temperature if necessary.
TIP: Advanced Image Processing
Professional image editing can be done with the GIMP. More information about
The GIMP can be found in Chapter 17, Manipulating Graphics with The GIMP
(page 225).
15.6
For More Information
For more information about using digital cameras with Linux, refer to the following
Web sites:
• http://digikam.sourceforge.net/—Information about Digikam
• http://www.gphoto.org—Information about gPhoto2
• http://www.gphoto.org/proj/libgphoto2/support.php—A
comprehensive list of supported cameras
• http://www.thekompany.com/projects/gphoto/—Information about
Kamera, a KDE front-end for gPhoto2
218
Kooka—A Scanning Application
16
Kooka is a KDE application for scanning. This chapter explains the user interface and
the functionality of the application. In addition to creating image files from printed
media, like photographs or magazines, Kooka has character recognition capabilities.
This means it can help convert written text to a text file that can be edited.
Start Kooka from the main menu or enter the command kooka. When started, Kooka
opens a three-frame window with a menu bar to the upper left and a toolbar directly
below it. All windows can be freely readjusted or rearranged with the mouse. It is also
possible to completely detach single frames from the Kooka window for deliberate
placement on the desktop. To move the frames, click and drag the thin double line right
above the frame. Any frame, except the main window, can be placed within any other
frame aligned to the left, right, top, bottom, or center. Centered windows have the same
size, are stacked, and can be brought to the foreground with tabs.
The Image Viewer and the Scan Preview frames share a window by default. Tabs allow
switching between them. The left frame provides the gallery. This is a small file
browser for accessing the scanned images. The frame to the lower right is shared by
OCR (optical character recognition) and the thumbnails, which can be loaded into the
image viewer with a simple click of the mouse. See Figure 16.1, “The Kooka Main
Window” (page 220).
Kooka—A Scanning Application
219
Figure 16.1
16.1
The Kooka Main Window
The Preview
A preview should always be created when the object to scan is smaller than the total
scanning area. Set a few parameters to the left of the preview frame. Select the scanning
size with Custom or one of the standard formats. See Figure 16.2, “The Kooka Preview
Window” (page 221). The Custom setting is the most flexible, because it allows selection
of the desired area with the mouse. Once the settings have been made, request the preview of the image to scan by clicking Preview Scan in Scan Parameters.
220
Figure 16.2
16.2
The Kooka Preview Window
The Final Scan
If you selected Custom for the scanning size, use the mouse to select the rectangular
area to scan. The selected area is confined by a dotted border.
Choose between color and black-and-white scanning and set the resolution with the
slider. See Figure 16.3, “The Kooka Scanning Parameters” (page 222). The higher the
resolution, the better the quality of the scanned image is. However, this also results in
a correspondingly larger file and the scanning process can take a very long time at high
resolutions. Activate Use custom gamma table and click Edit to change the settings for
brightness, contrast, and gamma.
Kooka—A Scanning Application
221
Figure 16.3
The Kooka Scanning Parameters
Once all settings have been made, click Final Scan to scan the image. The scanned
image is then displayed in the image viewer and as a thumbnail. When prompted, select
the format in which to save the image. To save all the future images in that same format,
check the corresponding box. Confirm with OK.
16.3
The Menus
Some of the functions of the toolbar are also available in the File and Image menus.
Modify preference settings for Kooka in Settings.
File
Use this menu to start the KPrinter printing assistant, create a new folder for your
images, and save, delete, and close files. The OCR results of a scanned text document
can be saved here. Also use this menu to close Kooka.
222
Image
The Image menu allows starting a graphics application for postprocessing or optical
character recognition of an image. The recognized text from an OCR operation is
displayed in its own frame. Various tools for scaling, rotating, and flipping an image
are available. These functions can also be accessed from the toolbar. Create From
Selection allows saving an area of an image previously marked with the mouse.
Settings
Settings adjusts of the look and feel of Kooka. The toolbar and status bar can be
switched on and off and keyboard shortcuts for menu entries can be defined. Configure Toolbars provides a list of all the functions available to the toolbar. Configure
Kooka opens a configuration dialog in which to modify the look and feel of Kooka.
Normally, however, the defaults are sufficient. In Tool Views, enable and disable
the thumbnail viewer, the preview, the gallery, the scanning parameters, and the
OCR result window.
Help
The Help menu provides access to the online help manual for Kooka. Also use it to
access a feedback channel for problems and wishes. It also provides information
about the version, authors, and license of Kooka and KDE.
16.4
The Gallery
The gallery window shows the default folder where Kooka stores all its image files.
An example is shown in Figure 16.4, “The Kooka Gallery” (page 223). To save an image
to your personal home directory, click the thumbnail to select it then select File → Save
Image. Then enter your personal home directory and give the file a descriptive name.
Figure 16.4
The Kooka Gallery
Kooka—A Scanning Application
223
To add images to the gallery, simply drag and drop them from Konqueror. Start Konqueror, navigate to the directory containing the images to add to the gallery, and drag
them with the mouse to a folder of the Kooka gallery.
16.5
Optical Character Recognition
If the character recognition module is installed, documents can be scanned in lineart
mode, saved in the proposed format, then processed for text recognition from the Image
menu. Process the entire document or only a previously selected area. A configuration
dialog tells the module whether the original text is in printed type, handwriting, or
standardized type. Also set the language so the module can process the document correctly. See Figure 16.5, “OCR with Kooka” (page 224).
Figure 16.5
OCR with Kooka
Switch to the OCR Result Text window and check the text, which may need to be
proofread. To do this, save the text with File → Save OCR Result Text. The text can
then be processed with OpenOffice.org or KWrite.
224
Manipulating Graphics with The
GIMP
17
The GIMP (The GNU Image Manipulation Program) is a program for creating and
editing pixel graphics. In most aspects, its features are comparable to those of Adobe
Photoshop and other commercial programs. Use it to resize and retouch photographs,
design graphics for Web pages, make covers for your custom CDs, or almost any other
graphics project. It meets the needs of both amateurs and professionals.
Like many other Linux programs, The GIMP is developed as a cooperative effort of
developers worldwide who volunteer their time and code to the project. The program
is under constant development, so the version included in your SUSE Linux may vary
slightly from the version discussed here. The layout of the individual windows and
window sections is especially likely to vary.
The GIMP is an extremely complex program. Only a small range of features, tools, and
menu items are discussed in this chapter. See Section 17.6, “For More Information”
(page 232) for ideas of where to find more information about the program.
17.1
Graphics Formats
There are two main formats for graphics—pixel and vector. The GIMP works only with
pixel graphics, which is the normal format for photographs and scanned images. Pixel
graphics consist of small blocks of color that together create the entire image. The files
can easily become quite large because of this. It is also not possible to increase the size
of a pixel image without losing quality.
Manipulating Graphics with The GIMP
225
Unlike pixel graphics, vector graphics do not store information for all individual pixels.
Instead, they store information about how image points, lines, or areas are grouped together. Vector images can also be scaled very easily. The drawing application of
OpenOffice.org, for example, uses this format.
17.2
Starting GIMP
Start GIMP from the main menu. Alternatively, enter gimp & in a command line.
17.2.1 Initial Configuration
When starting GIMP for the first time, a configuration wizard opens for preparatory
configuration. The default settings are acceptable for most purposes. Press Continue in
each dialog unless you are familiar with the settings and prefer another setup.
17.2.2 The Default Windows
Three windows appear by default. They can be arranged on the screen and, except the
toolbox, closed if no longer needed. Closing the toolbox closes the application. In the
default configuration, GIMP saves your window layout when you exit. Dialogs left
open reappear when you next start the program.
The Toolbox
The main window of GIMP, shown in Figure 17.1, “The Main Window” (page 227),
contains the main controls of the application. Closing it exits the application. At the
very top, the menu bar offers access to file functions, extensions, and help. Below that,
find icons for the various tools. Hover the mouse over an icon to display information
about it.
226
Figure 17.1
The Main Window
The current foreground and background color are shown in two overlapping boxes. The
default colors are black for the foreground and white for the background. Click the box
to open a color selection dialog. Swap the foreground and background color with the
bent arrow symbol to the upper right of the boxes. Use the black and white symbol to
the lower left to reset the colors to the default.
To the right, the current brush, pattern, and gradient are shown. Click the displayed one
to access the selection dialog. The lower portion of the window contains allows configuration of various options for the current tool.
Layers, Channels, Paths, Undo
In the first section, use the drop-down box to select the image to which the tabs refer.
By clicking Auto, control whether the active image is chosen automatically. By default,
Auto is enabled.
Manipulating Graphics with The GIMP
227
Layers shows the different layers in the current images and can be used to manipulate
the layers. Channels shows and can manipulate the color channels of the image.
Paths are an advanced method of selecting parts of an image. They can also be used
for drawing. Paths shows the paths available for an image and provides access to path
functions. Undo shows a limited history of modifications made to the current image.
The bottom portion of the window contains three tabs. With them, select the current
brush, gradient, and pattern.
17.3
Getting Started in GIMP
Although GIMP can be a bit overwhelming for new users, most quickly find it easy to
use once they work out a few basics. Crucial basic functions are creating, opening, and
saving images.
17.3.1 Creating a New Image
To create a new image, select File → New or press Ctrl + N . This opens a dialog in
which to make settings for the new image. If desired, use Template to select a template
on which to base the new image. The GIMP includes a number of templates, ranging
from an A4 sheet of paper to a CD cover, from which to choose. To create a custom
template, select File → Dialogs → Templates and use the controls offered by the window
that opens.
In the Image Size section, set the size of the image to create in pixels or another unit.
Click the unit to select another unit from the list of available units. The ratio between
pixels and a unit is set in Resolution, which appears when the Advanced Options section
is open. A resolution of 72 pixels per inch corresponds to screen display. It is sufficient
for Web page graphics. A higher resolution should be used for images to print. For
most printers, a resolution of 300 pixels per inch results in an acceptable quality.
In Colorspace, select whether the image should be in color (RGB) or Grayscale. Select
the Fill Type for the new image. Foreground Color and Background Color use the
colors selected in the toolbox. White uses a white background in the image. Transparent
creates a clear image. Transparency is represented by a gray checkerboard pattern.
Enter a comment for the new image in Comment.
228
When the settings meet your needs, press OK. To restore the default settings, press
Reset. Pressing Cancel aborts creation of a new image.
17.3.2 Opening an Existing Image
To open an existing image, select File → Open or press Ctrl + O . In the dialog that
opens, select the desired file. Click OK to open the selected image. Press Cancel to skip
opening an image.
17.3.3 The Image Window
The new or opened image appears in its own window. The menu bar in the top of the
window provides access to all image functions. Alternatively, access the menu by rightclicking the image or clicking the small arrow button in the left corner of the rulers.
File offers the standard file options, such as Save and Print. Close closes the current
image. Quit closes the entire application.
With the items in the View menu, control the display of the image and the image window.
New View opens a second display window of the current image. Changes made in one
view are reflected in all other views of that image. Alternate views are useful for magnifying a part of an image for manipulation while seeing the complete image in another
view. Adjust the magnification level of the current window with Zoom. When Shrink
Wrap is selected, the image window is resized to fit the current image display exactly.
17.4
Saving Images
No image function is as important as File → Save. It is better to save too often than too
rarely. Use File → Save as to save the image with a new filename. It is a good idea to
save image stages under different names or make backups in another directory so you
can easily restore a previous state.
When saving for the first time or using Save as, a dialog opens in which to specify the
filename and type. Enter the filename in the field at the top. For Save in folder, select
the directory in which to save the file from a list of commonly used directories. To use
a different directory or create a new one, open Browse for other folders. It is recommended to leave Select File Type set to By Extension. With that setting, GIMP determines
Manipulating Graphics with The GIMP
229
the file type based on the extension appended to the filename. The following file types
are frequently useful:
XCF
This is the native format of the application. It saves all layer and path information
along with the image itself. Even if you need an image in another format, it is usually a good idea to save a copy as XCF to simplify future modifications.
PAT
This is the format used for GIMP patterns. Saving an image in this format enables
using the image as a fill pattern in GIMP.
JPG
JPG or JPEG is a common format for photographs and Web page graphics without
transparency. Its compression method enables reduction of file sizes, but information
is lost when compressing. It may be a good idea to use the preview option when
adjusting the compression level. Levels of 85% to 75% often result in an acceptable
image quality with reasonable compression. Saving a backup in a lossless format,
like XCF, is also recommended. If editing an image, save only the finished image
as JPG. Repeatedly loading a JPG then saving can quickly result in poor image
quality.
GIF
Although very popular in the past for graphics with transparency, GIF is less often
used now because of license issues. GIF is also used for animated images. The format
can only save indexed images. The file size can often be quite small if only a few
colors are used.
PNG
With its support for transparency, lossless compression, free availability, and increasing browser support, PNG is replacing GIF as the preferred format for Web graphics
with transparency. An added advantage is that PNG offers partial transparency,
which is not offered by GIF. This enables smoother transitions from colored areas
to transparent areas (antialiasing).
To save the image in the chosen format, press Save. To abort, press Cancel. If the image
has features that cannot be saved in the chosen format, a dialog appears with choices
for resolving the situation. Choosing Export, if offered, normally gives the desired results. A window then opens with the options of the format. Reasonable default values
are provided.
230
17.5
Printing Images
To print an image, select File → Print from the image menu. If your printer is configured
in SUSE Linux, it should appear in the list. In some cases, it may be necessary to select
an appropriate driver with Setup Printer. Select the appropriate paper size with Media
Size and the type in Media Type. Other settings are available in the Image / Output
Settings tab.
Figure 17.2
The Print Dialog
In the bottom portion of the window, adjust the image size. Press Use Original Image
Size to take these settings from the image itself. This is recommended if you set an appropriate print size and resolution in the image. Adjust the image's position on the page
with the fields in Position or by dragging the image in Preview.
When satisfied with the settings, press Print. To save the settings for future use, instead
use Print and Save Settings. Cancel aborts printing.
Manipulating Graphics with The GIMP
231
17.6
For More Information
The following are some resources that may be useful for a GIMP user. Unfortunately,
many resources apply to older versions.
• Help provides access to the internal help system. This documentation is also
available in HTML and PDF formats at http://docs.gimp.org.
• The GIMP User Group offers an informative and interesting Web site at http://
gug.sunsite.dk.
• http://www.gimp.org is the official home page of The GIMP.
• Grokking the GIMP by Carey Bunks is an excellent book based on an older GIMP
version. Although some aspects of the program have changed, it can provide excellent guidance for image manipulation. An online version is available at http://
gimp-savvy.com/BOOK/.
• http://gimp-print.sourceforge.net is the Web page for the GIMP
print plug-in. The user manual available from the site provides detailed information
about configuring and using the program.
232
Part VI Mobility
Mobile Computing with Linux
18
This chapter provides an overview of the various aspects of using Linux for mobile
computing. The various fields of use are briefly introduced and the essential features
of the employed hardware are described. Software solutions for special requirements
and options for maximum performance are covered along with possibilities to minimize
power consumption. An overview of the most important sources of information about
the subject concludes the chapter.
Most people associate mobile computing with laptops, PDAs, and cellular phones and
the data exchange between them. This chapter extends the focus to mobile hardware
components, such as external hard disks, flash drives, or digital cameras, which can be
connected to laptops or desktop systems.
18.1
Laptops
The hardware of laptops differs from that of a normal desktop system. This is because
criteria like exchangeability, occupied space, and power consumption are relevant
properties. The manufacturers of mobile hardware have developed the PCMCIA (Personal Computer Memory Card International Association) standard. This standard covers
memory cards, network interface cards, ISDN and modem cards, and external hard
disks. How the support for such hardware is implemented in Linux, what needs to be
taken into account during configuration, what software is available for the control of
PCMCIA, and how to troubleshoot any possible problems is described in Chapter 19,
PCMCIA (page 245).
Mobile Computing with Linux
235
18.1.1 Power Conservation
The inclusion of energy-optimized system components when manufacturing laptops
contributes to their suitability for use without access to the electrical power grid. Their
contribution towards conservation of power is at least as important as that of the operating system. SUSE Linux supports various methods that influence the power consumption of a laptop and have varying effects on the operating time under battery power.
The following list is in descending order of contribution towards power conservation:
• Throttling the CPU speed
• Switching off the display illumination during pauses
• Manually adjusting the display illumination
• Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external
mouse, unused PCMCIA cards, etc.)
• Spinning down the hard disk when idling
Detailed background information about power management in SUSE Linux and about
operating the YaST power management module is provided in Chapter 21, Power
Management (page 259).
18.1.2 Integration in Changing Operating
Environments
Your system needs to adapt to changing operating environments when used for mobile
computing. A lot of services depend on the environment and the underlying clients
must be reconfigured. SUSE Linux takes over this job for you.
236
Figure 18.1
Integrating a Laptop in a Network
?
?
Printing
Mail
?
?
?
?
?
?
Proxy
X configuration
Network
The services affected in the case of a laptop commuting back and forth between a small
home network and an office network are:
Network Configuration
This includes IP address assignment, name resolution, Internet connectivity, and
connectivity to other networks.
Printing
A current database of available printers and an available print server must be present,
depending on the network.
E-Mail and Proxies
As with printing, the list of the corresponding servers must be current.
Configuring X
If your laptop is temporarily connected to a beamer or an external monitor, the different display configurations must be available.
Mobile Computing with Linux
237
SUSE Linux offers two ways of integrating a laptop into existing operating environments.
They can be combined.
SCPM
SCPM (system configuration profile management) allows storage of arbitrary configuration states of a system into a kind of “snapshot” called a profile. Profiles can
be created for different situations. They are useful when a system is operated in
changing environments (home network, office network). It is always possible to
switch between profiles. Information about SCPM can be found in Chapter 20,
System Configuration Profile Management (page 247). The kicker applet Profile
Chooser in KDE allows switching between profiles. The application requires the
root password before switching.
SLP
The service location protocol (SLP) simplifies the connection of a laptop to an existing network. Without SLP, the administrator of a laptop usually requires detailed
knowledge of the services available in a network. SLP broadcasts the availability
of a certain type of service to all clients in a local network. Applications that support
SLP can process the information dispatched by SLP and be configured automatically.
SLP can even be used for the installation of a system and spare the effort of
searching for a suitable installation source. Detailed information about SLP can be
found in Chapter 39, SLP Services in the Network (page 589).
The emphasis of SCPM lies on enabling and maintaining reproducible system conditions.
SLP makes configuration of a networked computer a lot easier by automating much of
it.
18.1.3 Software Options
There are various special task areas in mobile use that are covered by dedicated software:
system monitoring (especially the battery charge), data synchronization, and wireless
communication with peripherals and the Internet. The following sections cover the most
important applications that SUSE Linux provides for each task.
System Monitoring
Two KDE system monitoring tools are provided by SUSE Linux. The pure status display
of the rechargeable battery of the laptop is handled by the applet KPowersave in the
kicker. Complex system monitoring is performed by KSysguard. When using GNOME,
238
the described functions are provided by GNOME ACPI (as panel applet) and System
Monitor.
KPowersave
KPowersave is an applet that displays the state of the rechargeable battery in the
control panel. The icon adjusts to represent the type of power supply. When working
on AC power, a small plug icon is displayed. When working on batteries, the icon
changes to a battery. The corresponding menu opens the YaST module for power
management after requesting the root password. This allows setting the behavior
of the system under different types of power supply. Information about power
management and about the corresponding YaST module can be found in Chapter 21,
Power Management (page 259).
KSysguard
KSysguard is an independent application that gathers all measurable parameters of
the system into one monitoring environment. KSysguard has monitors for ACPI
(battery status), CPU load, network, partitioning, and memory usage. It can also
watch and display all system processes. The presentation and filtering of the collected
data can be customized. It is possible to monitor different system parameters in
various data pages or collect the data of various machines in parallel over the network. KSysguard can also run as a daemon on machines without a KDE environment.
More information about this program is provided in its integrated help function or
in the SUSE help pages.
Figure 18.2
Monitoring the Battery State with KSysguard
Mobile Computing with Linux
239
Synchronizing Data
When switching between working on a mobile machine disconnected from the network
and working at a networked workstation in an office, it is necessary to keep processed
data synchronized across all instances. This could include e-mail folders, directories,
and individual files that need to be present for work on the road as well as at the office.
The solution in both cases is as follows:
Synchronization of E-Mail
Use an IMAP account for storing your e-mails in the office network. The e-mails
are then accesssed from the workstation using any disconnected IMAP–enabled email client, like Mozilla Thunderbird Mail, Evolution, or KMail as described in the
Start-Up. The e-mail client must be configured so that the same folder is always
accessed for Sent messages. This ensures that all messages are available along
with their status information after the synchronization process has completed. Use
an SMTP server implemented in the mail client for sending messages instead of the
systemwide MTA postfix or sendmail to receive reliable feedback about unsent
mail.
Synchronizing Files and Directories
There are several utilities suitable for synchronizing data between a laptop and a
workstation. For detailed information, refer to Chapter 47, File Synchronization
(page 715).
Wireless Communication
As well as connecting to a home or office network with a cable, a laptop can also
wirelessly connected to other computers, peripherals, cellular phones, or PDAs. Linux
supports three types of wireless communication:
WLAN
With the largest range of these wireless technologies, WLAN is the only one suitable
for the operation of large and sometimes even spatially disjointed networks. Single
machines can connect with each other to form an independent wireless network or
access the Internet. Devices called access points act as base stations for WLANenabled devices and act as intermediate for access to the Internet. A mobile user
can switch among access points depending on location and which access point is
offering the best connection. Like in cellular telephony, a large network is available
240
to WLAN users without binding them to a specific location for accessing it. Details
about WLAN can be found in Section 22.1, “Wireless LAN” (page 283).
Bluetooth
Bluetooth has the broadest application spectrum of all wireless technologies. It can
be used for communication between computers (laptops) and PDAs or cellular
phones, as can IrDA. It can also be used to connect various computers within visible
range. Bluetooth is also used to connect wireless system components, like a keyboard
or mouse. The range of this technology is, however, not sufficient to connect remote
systems to a network. WLAN is the technology of choice for communicating through
physical obstacles like walls. More information about Bluetooth, its applications,
and configuration can be found in Section 22.2, “Bluetooth” (page 293).
IrDA
IrDA is the wireless technology with the shortest range. Both communication parties
must be within viewing distance of each other. Obstacles like walls cannot be
overcome. One possible application of IrDA is the transmission of a file from a
laptop to a cellular phone. The short path from the laptop to the cellular phone is
then covered using IrDA. The long range transport of the file to the recipient of the
file is handled by the mobile network. Another application of IrDA is the wireless
transmission of printing jobs in the office. More information about IrDA can be
found in Section 22.3, “Infrared Data Transmission” (page 304).
18.1.4 Data Security
Ideally, you protect data on your laptop against unauthorized access in multiple ways.
Possible security measures can be taken in the following areas:
Protection against Theft
Always physically secure your system against theft whenever possible. Various
securing tools, like chains, are available in retail stores.
Securing Data on the System
Important data should not only be encrypted during transmission, but also on the
hard disk. This ensures its safety in case of theft. The creation of an encrypted partition with SUSE Linux is described in Section 23.3, “Encrypting Partitions and
Files” (page 325).
Mobile Computing with Linux
241
IMPORTANT: Data Security and Suspend to Disk
Encrypted partitions are not unmounted during a suspend to disk event.
Thus, all data on these partitions is available to any party who manages to
steal the hardware and issue a resume of the hard disk.
Network Security
Any transfer of data should be secured, no matter how it takes place. General security issues regarding Linux and networks can be found in Section 23.4, “Security
and Confidentiality” (page 328). Security measures related to wireless networking
are provided in Chapter 22, Wireless Communication (page 283).
18.2
Mobile Hardware
SUSE Linux supports the automatic detection of mobile storage devices over firewire
(IEEE 1394) or USB. The term mobile storage device applies to any kind of firewire
or USB hard disk, USB flash drive, or digital camera. These devices are automatically
detected and configured via hotplug as soon as they are connected with the system over
the corresponding interface. subfs and submount ensure that the devices are mounted
to the corresponding locations in the file system. The user is completely spared the
manual mounting and unmounting that was found in previous versions of SUSE Linux.
A device can simply be disconnected as soon as no program accesses it.
External Hard Disks (USB and Firewire)
As soon as an external hard disk has been correctly recognized by the system, its
icon appears in My Computer (KDE) or Computer (GNOME) in the list of mounted
drives. Clicking the icon displays the contents of the drive. It is possible to create
folders and files here and edit or delete them. To rename a hard disk from the name
it had been given by the system, select the corresponding menu item from the menu
that opens when the icon is right-clicked. This name change is limited to display in
the file manager. The descriptor by which the device is mounted in /media/
usb-xxx or /media/ieee1394-xxx remains unaffected by this.
USB Flash Drives
These devices are handled by the system just like external hard disks. It is similarly
possible to rename the entries in the file manager.
242
Digital Cameras (USB and Firewire)
Digital cameras recognized by the system also appear as external drives in the
overview of the file manager. KDE allows reading and accessing the pictures at the
URL camera:/. The images can then be processed using Digikam or The GIMP.
When using GNOME, Nautilus displays the pictures in their own folder. A simple
image processing and management utility is f-spot. Advanced photo processing is
done with The GIMP. For more details on digital cameras and image management,
refer to Chapter 15, Digital Cameras and Linux (page 201).
18.3
Cellular Phones and PDAs
A desktop system or a laptop can communicate with a cellular phone via Bluetooth or
IrDA. Some models support both protocols and some only one of the two. The usage
areas for the two protocols and the corresponding extended documentation has already
been mentioned in Section “Wireless Communication” (page 240). The configuration
of these protocols on the cellular phones themselves is described in their manuals. The
configuration of the Linux side is described in Section 22.2, “Bluetooth” (page 293) and
Section 22.3, “Infrared Data Transmission” (page 304).
The support for syncronizing with handheld devices manufactured by Palm, Inc., is already built into Evolution and Kontact. Initial connection with the device is, in both
cases, easily performed with the assistance of a wizard. Once the support for Palm Pilots
is configured, it is necessary to determine which type of data should be synchronized
(addresses, appointments, etc.). Both groupware applications are described in the StartUp.
The program KPilot as integrated in Kontact is also available as an independent utility.
It is described in the Start-Up. The program KitchenSync is also available for synchronizing address data.
18.4
For More Information
The central point of reference for all questions regarding mobile devices and Linux is
http://tuxmobil.org/. Various sections of that Web site deal with the hardware
and software aspects of laptops, PDAs, cellular phones, and other mobile hardware.
Mobile Computing with Linux
243
A similar approach to that of http://tuxmobil.org/ is made by http://www
.linux-on-laptops.com/. Information about laptops and handhelds can be
found here.
SUSE maintains a mailing list in German dedicated to the subject of laptops. See
http://lists.suse.com/archive/suse-laptop/. On this list, users and
developers discuss all aspects of mobile computing with SUSE Linux. Postings in English are answered, but the majority of the archived information is only available in
German.
In the case of problems with power management with SUSE Linux on laptops, it is
advisable to read the file README in /usr/share/doc/packages/powersave.
This directory often contains last minute feedback by testers and developers, so provides
valuable hints for the solution of problems.
244
PCMCIA
19
This section covers special aspects of PCMCIA hardware and software as found in
laptops. PCMCIA stands for Personal Computer Memory Card International Association
and is used as a collective term for all related hardware and software.
19.1
Hardware
The most important component is the PCMCIA card. There are two types of PCMCIA
cards:
PC Cards
These cards have been around since the dawn of PCMCIA. They use a 16-bit bus
for the data transmission and are usually quite inexpensive. Some modern PCMCIA
bridges have difficulties detecting these cards. Nevertheless, once they are detected,
they usually run smoothly and do not cause any problems.
CardBus Cards
This is a more recent standard. They use a 32-bit bus, which makes them faster but
also more expensive. They are integrated in the system like PCI cards and also run
smoothly.
The second important component is the PCMCIA controller or the PC card or CardBus
bridge, which establishes the connection between the card and the PCI bus. All common
models are supported. If it is a built-in PCI device, the command lspci -vt provides
further information.
PCMCIA
245
19.2
Software
With the current kernel, PCMCIA bridges and PCMCIA cards are handled by the hotplug
subsystem. There are pcmcia_socket events for every bridge and pcmcia events.
udevd loads all needed modules and calls the necessary tools to set up these devices.
These actions are defined in /etc/udev/rules.d/.
/etc/pcmcia/config.opts is used for resource configuration. The needed
driver is determined by device tables in the drivers. Information about the current state
of the sockets and the cards can be found in /sys/class/pcmcia_socket/ and
via pccardctl.
Because there are ongoing changes in the PCMCIA system, this documentation is incomplete. For a comprehensive overview, refer to /usr/share/doc/packages/
pcmciautils/README.SUSE.
246
System Configuration Profile
Management
20
With the help of SCPM (system configuration profile management), adapt the configuration of your computer to different operating environments or hardware configurations.
SCPM manages a set of system profiles for the different scenarios. SCPM enables easy
switching between system profiles, eliminating the need for manually reconfiguring
the system.
Some situations require a modified system configuration. This would mostly be the
case for mobile computers that are operated in varying locations. If a desktop system
should be operated temporarily using other hardware components than usual, SCPM
comes in handy. Restoring the original system configuration should be easy and the
modification of the system configuration can be reproduced. With SCPM, any part of
the system configuration can be kept in a customized profile.
The main field of application of SCPM is network configuration on laptops. Different
network configurations often require different settings of other services, such as e-mail
or proxies. Then other elements follow, like different printers at home and at the office,
a customized X server configuration for the multimedia projector at conferences, special
power-saving settings for the road, or a different time zone at an overseas subsidiary.
20.1
Terminology
The following are some terms used in SCPM documentation and in the YaST module.
System Configuration Profile Management
247
• The term system configuration refers to the complete configuration of the computer.
It covers all fundamental settings, such as the use of hard disk partitions, network
settings, time zone selection, and keyboard mappings.
• A profile, also called configuration profile, is a state that has been preserved and
can be restored at any time.
• Active profile refers to the profile last selected. This does not mean that the current
system configuration corresponds exactly to this profile, because the configuration
can be modified at any time.
• A resource in the SCPM context is an element that contributes to the system configuration. This can be a file or a softlink including metadata (like the user), permissions, or access time. This can also be a system service that runs in this profile, but
is deactivated in another one.
• Every resource belongs to a certain resource group. These groups contain all resources that logically belong together—most groups would contain both a service
and its configuration files. It is very easy to assemble resources managed by SCPM
because this does not require any knowledge of the configuration files of the desired
service. SCPM ships with a selection of preconfigured resource groups that should
be sufficient for most scenarios.
20.2
Using the YaST Profile Manager
Start the YaST profile manager from the YaST control center with System → Profile
Manager. On first start, explicitly enable SCPM by selecting Enabled in the SCPM
Options dialog, shown in Figure 20.1, “YaST SCPM Options” (page 249). In Settings,
determine whether progress pop-ups should be closed automatically and whether to
display verbose messages about the progress of your SCPM configuration. For Switch
Mode, determine whether modified resources of the active profile should be saved or
discarded when the profile is switched. If Switch Mode is set to Normal, all changes in
the active profile are saved when switched. To define the behavior of SCPM at boot
time, set Boot Mode to Save Changes (default setting) or to Drop Changes.
248
Figure 20.1
YaST SCPM Options
20.2.1 Configuring Resource Groups
To make changes to the current resource configuration, choose Configure Resources
in the SCPM Options dialog. The next dialog, shown in Figure 20.2, “Configuring Resource Groups” (page 250), lists all resource groups available on your system. To add
or edit a resource group, specify or modify Resource Group and Description. For an
LDAP service, for example, enter ldap as Resource Group and LDAP client
service as Description. Then enter the appropriate resources (services, configuration
files, or both) or modify the existing ones. Delete those that are not used. To reset the
status of the selected resources—discard any changes made to them and return to the
initial configuration values—choose Reset Group. Your changes are saved to the active
profile.
System Configuration Profile Management
249
Figure 20.2
Configuring Resource Groups
20.2.2 Creating a New Profile
To create a new profile, click Add in the start dialog (System Configuration Profile
Management). In the window that opens, select whether the new profile should be based
on the current system configuration (SCPM automatically retrieves the current configuration and writes it to your profile) or on an existing profile. If you use the current
system configuration as the base of the new profile, you can mark the new profile as
the new active profile. This makes no changes to the old profile and does not start or
stop any services.
Provide a name and a short description for the new profile in the following dialog. For
SCPM to execute special scripts on a switch of profiles, enter the paths to each executable (see Figure 20.3, “Special Profile Settings” (page 251)). Refer to Section 20.3.4,
“Advanced Profile Settings” (page 254) for more information. SCPM runs a check for
the resources of the new profile. After this test has been successfully completed, the
new profile is ready for use.
250
Figure 20.3
Special Profile Settings
20.2.3 Modifying Existing Profiles
To modify an existing profile, choose Edit in the start dialog (System Configuration
Profile Management). Then modify the name, description, scripts, and resources according to your needs.
20.2.4 Switching Profiles
To switch profiles, open the profile manager. The active profile is marked with an arrow.
Select the profile to which to switch and click Switch To. SCPM checks for new or
modified resources and adds them, if necessary.
If a resource has been modified, YaST opens the Confirm Switch dialog. Modified Resource Groups of Active Profile lists all resource groups of the active profile that have
been modified but not yet saved to the active profile. Save or Ignore for the currently
selected resource group determines whether changes to this resource group should be
saved to the active profile or discarded. Alternatively, select each resource and click
Details to analyze the changes in detail. This shows a list of all configuration files or
executables belonging to this resource group that have been modified. To get a line-by-
System Configuration Profile Management
251
line comparison of the old and new version, click Show Changes. After analyzing the
changes, decide what to do with them in Action:
Save Resource
Save this resource to the active profile, but leave all other profiles untouched.
Ignore Resource
Leave the active resource untouched. This change is discarded.
Save to All Profiles
Copy the entire configuration of this resource to all other profiles.
Patch All Profiles
Apply only the most recent changes to all profiles.
Save or Ignore All just saves or discards the changes of all resources shown in this dialog.
After confirming the changes to the active profile, leave the Confirm Switch dialog by
clicking OK. SCPM then switches to the new profile. While switching, it executes the
prestop and poststop scripts of the old profile and the prestart and poststart scripts for
the new profile.
20.3
Configuring SCPM Using the
Command Line
This section introduces the command-line configuration of SCPM. Learn how to start
it, configure it, and work with profiles.
20.3.1 Starting SCPM and Defining
Resource Groups
SCPM must be activated before use. Activate SCPM with scpm enable. When run
for the first time, SCPM is initialized, which takes a few seconds. Deactivate SCPM
with scpm disable at any time to prevent the unintentional switching of profiles.
A subsequent reactivation simply resumes the initialization.
252
By default, SCPM handles network and printer settings as well as the X.Org configuration. To manage special services or configuration files, activate the respective resource
groups. To list the predefined resource groups, use scpm list_groups. To see
only the groups already activated, use scpm list_groups -a. Issue these commands as root on the command line.
scpm list_groups -a
nis
mail
ntpd
xf86
autofs
network
printer
Network Information Service client
Mail subsystem
Network Time Protocol daemon
X Server settings
Automounter service
Basic network settings
Printer settings
Activate or deactivate a group with scpm activate_group NAME or scpm
deactivate_group NAME. Replace NAME with the relevant group name.
20.3.2 Creating and Managing Profiles
A profile named default already exists after SCPM has been activated. Get a list of
all available profiles with scpm list. This one existing profile is also the active one,
which can be verified with scpm active. The profile default is a basic configuration from which the other profiles are derived. For this reason, all settings that should
be identical in all profiles should be made first. Then store these modifications in the
active profile with scpm reload. The default profile can be copied and renamed
as the basis for new profiles.
There are two ways to add a new profile. If the new profile (named work here) should
be based on the profile default, create it with scpm copy default work. The
command scpm switch work changes into the new profile, which can then be
modified. You may want to modify the system configuration for special purposes and
save the changes to a new profile. The command scpm add work creates a new
profile by saving the current system configuration in the profile work and marking it
as active. Running scpm reload then saves changes to the profile work.
Profiles can be renamed or deleted with the commands scpm rename x y and
scpm delete z. For example, to rename work to project, enter scpm rename
work project. To delete project, enter scpm delete project. The active
profile cannot be deleted.
System Configuration Profile Management
253
20.3.3 Switching Configuration Profiles
The command scpm switch work switches to another profile (the profile work,
in this case). Switch to the active profile to include modified settings of the system
configuration in the profile. This corresponds to the command scpm reload.
When switching profiles, SCPM first checks which resources of the active profile have
been modified. It then queries whether the modification of each resource should be
added to the active profile or dropped. If you prefer a separate listing of the resources
(as in former versions of SCPM), use the switch command with the -r parameter:
scpm switch -r work.
scpm switch -r work
Checking for modified resources
Checking for Resources to be started/shut down
Checking for dependencies
Restoring profile default
SCPM then compares the current system configuration with the profile to which to
switch. In this phase, SCPM evaluates which system services need to be stopped or
restarted due to mutual dependencies or to reflect the changes in configuration. This is
like a partial system reboot that concerns only a small part of the system while the rest
continues operating without change. It is only at this point that the system services are
stopped, all modified resources, such as configuration files, are written, and the system
services are restarted.
20.3.4 Advanced Profile Settings
You can enter a description for every profile that is displayed with scpm list. For
the active profile, set it with scpm set description "text". Provide the name
of the profile for inactive profiles, for example, scpm set description "text"
work. Sometimes it might be desirable to perform additional actions not provided by
SCPM while switching profiles. Attach up to four executables for each profile. They
are invoked at different stages of the switching process. These stages are referred to as:
prestop
prior to stopping services when leaving the profile
254
poststop
after stopping services when leaving the profile
prestart
prior to starting services when activating the profile
poststart
after starting services when activating the profiles
Insert these actions with the command set by entering scpm set prestop
filename, scpm set poststop filename, scpm set prestart
filename, or scpm set poststart filename. The scripts must be executable
and refer to the correct interpreter.
WARNING: Integrating a Custom Script
Additional scripts to be executed by SCPM must be made readable and executable for the superuser (root). The access to these files must be blocked
for all other users. Enter the commands chmod 700 filename and chown
root:root filename to give root exclusive permissions to the files.
Query all additional settings entered with set with get. The command scpm get
poststart, for example, returns the name of the poststart call or simply nothing if
nothing has been attached. Reset such settings by overwriting with "". The command
scpm set prestop "" removes the attached prestop program.
All set and get commands can be applied to an arbitrary profile in the same manner
as comments are added. For example, scpm get prestop filename work or
scpm get prestop work.
20.4
Using the Profile Chooser
Applet
The Profile Chooser applet in your GNOME or KDE desktop panel allows you to easily
control your SCPM settings. Create, modify or delete profiles via YaST as described
in Section 20.2, “Using the YaST Profile Manager” (page 248) and switch profiles.
Switching profiles can be done as normal user provided the system administrator allows
System Configuration Profile Management
255
this to happen. Start Profile Chooser from your desktop menu using System → Desktop
Applet → Profile Chooser.
Enable normal users to switch profiles by right-clicking the Profile Chooser icon in the
desktop panel and choosing Allow user switching from the menu that opens. Provide
the root password. Any authorized user on your system can switch profiles from now
on.
All profiles configured in YaST, either directly via a YaST call or via the Start YaST2
Profile Manager Module are displayed after you click the Profile Chooser icon. Select
the one to switch to using the cursor keys and SCPM changes to the new profile automatically.
20.5
Troubleshooting
This section covers frequent problems encountered with SCPM. Learn how they can
arise and how you can solve these issues.
20.5.1 Termination During the Switch
Process
Sometimes SCPM stops working during a switch procedure. This may be caused by
some outside effect, such as a user abort, a power failure, or even an error in SCPM itself.
If this happens, an error message stating SCPM is locked appears the next time you
start SCPM. This is for system safety, because the data stored in its database may differ
from the state of the system. To resolve this issue, run scpm recover. SCPM performs all missing operations of the previous run. You can also run scpm recover
-b, which tries to undo all already performed operations of the previous run. If you are
using the YaST profile manager, get a recover dialog on start-up that offers to perform
the commands described above.
256
20.5.2 Changing the Resource Group
Configuration
To modify the configuration of the resource group when SCPM is already initialized,
enter scpm rebuild after adding or removing groups. In this way, new resources
are added to all profiles and the removed resources are deleted permanently. If the
deleted resources are configured differently in the various profiles, this configuration
data is lost, except for the current version in your system, which SCPM does not touch.
If you modify the configuration with YaST, the rebuild command does not need to be
entered, because this is handled by YaST.
20.6
Selecting a Profile When
Booting the System
To select a profile when booting the system, press F3 in the boot screen to access a list
of available profiles. Use the arrow keys to select a profile and confirm your selection
with Enter . The selected profile is then used as a boot option.
20.7
For More Information
The latest documentation is available in the SCPM info pages (info scpm). Information
for developers is available in /usr/share/doc/packages/scpm.
System Configuration Profile Management
257
21
Power Management
Power management is especially important on laptop computers, but is also useful on
other systems. Two technologies are available: APM (advanced power management)
and ACPI (advanced configuration and power interface). In addition to these, it is also
possible to control CPU frequency scaling to save power or decrease noise. These options
can be configured manually or using a special YaST module.
Unlike APM, which was previously used on laptops for power management only, the
hardware information and configuration tool ACPI is available on all modern computers
(laptops, desktops, and servers). All power management technologies require suitable
hardware and BIOS routines. Most laptops and many modern desktops and servers
meet these requirements.
APM had been used in many older computers. Because APM largely consists of a
function set implemented in the BIOS, the level of APM support may vary depending
on the hardware. This is even more true of ACPI, which is even more complex. For
this reason, it is virtually impossible to recommend one over the other. Simply test the
various procedures on your hardware then select the technology that is best supported.
IMPORTANT: Power Management for AMD64 Processors
AMD64 processors with a 64-bit kernel only support ACPI.
Power Management
259
21.1
Power Saving Functions
Power saving functions are not only significant for the mobile use of laptops, but also
for desktop systems. The main functions and their use in the power management systems
APM and ACPI are:
Standby
This operating mode turns off the display. On some computers, the processor performance is throttled. This function is not available in all APM implementations.
This function corresponds to the ACPI state S1 or S2.
Suspend (to memory)
This mode writes the entire system state to the RAM. Subsequently, the entire system
except the RAM is put to sleep. In this state, the computer consumes very little
power. The advantage of this state is the possibility of resuming work at the same
point within a few seconds without having to boot and restart applications. Devices
using APM can usually be suspended by closing the lid and activated by opening
it. This function corresponds to the ACPI state S3. The support of this state is still
under development and therefore largely depends on the hardware.
Hibernation (suspend to disk)
In this operating mode, the entire system state is written to the hard disk and the
system is powered off. Reactivation from this state takes about 30 to 90 seconds.
The state prior to the suspend is restored. Some manufacturers offer useful hybrid
variants of this mode, such as RediSafe in IBM Thinkpads. The corresponding ACPI
state is S4. In Linux, suspend to disk is performed by kernel routines that are independent from APM and ACPI.
Battery Monitor
ACPI and APM check the battery charge status and provide information about the
charge status. Additionally, both systems coordinate actions to perform when a
critical charge status is reached.
Automatic Power-Off
Following a shutdown, the computer is powered off. This is especially important
when an automatic shutdown is performed shortly before the battery is empty.
Shutdown of System Components
Switching off the hard disk is the greatest single aspect of the power saving potential
of the overall system. Depending on the reliability of the overall system, the hard
260
disk can be put to sleep for some time. However, the risk of losing data increases
with the duration of the sleep periods. Other components can be deactivated via
ACPI (at least theoretically) or permanently in the BIOS setup.
Processor Speed Control
In connection with the CPU, energy can be saved in three different ways: frequency
and voltage scaling (also known as PowerNow! or Speedstep), throttling, and putting
the processor to sleep (C states). Depending on the operating mode of the computer,
these methods can also be combined.
21.2
APM
Some of the power saving functions are performed by the APM BIOS itself. On many
laptops, standby and suspend states can be activated with key combinations or by
closing the lid without any special operating system function. However, to activate
these modes with a command, certain actions must be triggered before the system is
suspended. To view the battery charge level, you need special program packages and
a suitable kernel.
SUSE Linux kernels have built-in APM support. However, APM is only activated if
ACPI is not implemented in the BIOS and an APM BIOS is detected. To activate APM
support, ACPI must be disabled with acpi=off at the boot prompt. Enter cat
/proc/apm to check if APM is active. An output consisting of various numbers indicates that everything is OK. You should now be able to shut down the computer with
the command shutdown -h.
BIOS implementations that are not fully standard-compliant can cause problems with
APM. Some problems can be circumvented with special boot parameters. All parameters
are entered at the boot prompt in the form apm=parameter:
on or off
Enable or disable APM support.
(no-)allow-ints
Allow interrupts during the execution of BIOS functions.
(no-)broken-psr
The “GetPowerStatus” function of the BIOS does not work properly.
Power Management
261
(no-)realmode-power-off
Reset processor to real mode prior to shutdown.
(no-)debug
Log APM events in system log.
(no-)power-off
Power system off after shutdown.
bounce-interval=n
Time in hundredths of a second after a suspend event during which additional suspend events are ignored.
idle-threshold=n
System inactivity percentage from which the BIOS function idle is executed
(0=always, 100=never).
idle-period=n
Time in hundredths of a second after which the system activity is measured.
The APM daemon (apmd) is no longer used. Its functionality is now handled by the
new powersaved, which also supports ACPI and CPU frequency scaling.
21.3
ACPI
ACPI (advanced configuration and power interface) was designed to enable the operating
system to set up and control the individual hardware components. ACPI supersedes
both PnP and APM. It delivers information about the battery, AC adapter, temperature,
fan, and system events, like “close lid” or “battery low.”
The BIOS provides tables containing information about the individual components and
hardware access methods. The operating system uses this information for tasks like
assigning interrupts or activating and deactivating components. Because the operating
system executes commands stored in the BIOS, the functionality depends on the BIOS
implementation. The tables ACPI can detect and load are reported in /var/log/boot
.msg. See Section 21.3.4, “Troubleshooting” (page 267) for more information about
troubleshooting ACPI problems.
262
21.3.1 ACPI in Action
If the kernel detects an ACPI BIOS when the system is booted, ACPI is activated automatically and APM is deactivated. The boot parameter acpi=force may be necessary
for some older machines. The computer must support ACPI 2.0 or later. Check the
kernel boot messages in /var/log/boot.msg to see if ACPI was activated.
Subsequently, a number of modules must be loaded. This is done by the start script of
the powersave daemon. If any of these modules cause problems, the respective module
can be excluded from loading or unloading in /etc/sysconfig/powersave/
common. The system log (/var/log/messages) contains the messages of the
modules, enabling you to see which components were detected.
/proc/acpi now contains a number of files that provide information about the system
state or can be used to change some of the states. Some features do not work yet because
they are still under development and the support of some functions largely depends on
the implementation of the manufacturer.
All files (except dsdt and fadt) can be read with cat. In some files, settings can be
modified with echo, for example, echo X > file to specify suitable values for
X. Always use the command powersave to access this information and control options.
The following describes the most important files:
/proc/acpi/info
General information about ACPI.
/proc/acpi/alarm
Here, specify when the system should wake from a sleep state. Currently, this feature
is not fully supported.
/proc/acpi/sleep
Provides information about possible sleep states.
/proc/acpi/event
All events are reported here and processed by the Powersave daemon
(powersaved). If no daemon accesses this file, events, such as a brief click on
the power button or closing the lid, can be read with cat /proc/acpi/event
(terminate with Ctrl + C ).
Power Management
263
/proc/acpi/dsdt and /proc/acpi/fadt
These files contain the ACPI tables DSDT (differentiated system description table)
and FADT (fixed ACPI description table). They can be read with acpidmp,
acpidisasm, and dmdecode. These programs and their documentation are located in the package pmtools. For example, acpidmp DSDT | acpidisasm.
/proc/acpi/ac_adapter/AC/state
Shows whether the AC adapter is connected.
/proc/acpi/battery/BAT*/{alarm,info,state}
Detailed information about the battery state. The charge level is read by comparing
the last full capacity from info with the remaining capacity
from state. A more comfortable way to do this is to use one of the special programs
introduced in Section 21.3.3, “ACPI Tools” (page 267). The charge level at which
a battery event is triggered can be specified in alarm.
/proc/acpi/button
This directory contains information about various switches.
/proc/acpi/fan/FAN/state
Shows if the fan is currently active. Activate or deactivate the fan manually by
writing 0 (on) or 3 (off) into this file. However, both the ACPI code in the kernel
and the hardware (or the BIOS) overwrite this setting when it gets too warm.
/proc/acpi/processor/*
A separate subdirectory is kept for each CPU included in your system.
/proc/acpi/processor/*/info
Information about the energy saving options of the processor.
/proc/acpi/processor/*/power
Information about the current processor state. An asterisk next to C2 indicates that
the processor is idle. This is the most frequent state, as can be seen from the usage
value.
/proc/acpi/processor/*/throttling
Can be used to set the throttling of the processor clock. Usually, throttling is possible
in eight levels. This is independent of the frequency control of the CPU.
264
/proc/acpi/processor/*/limit
If the performance (outdated) and the throttling are automatically controlled by a
daemon, the maximum limits can be specified here. Some of the limits are determined
by the system. Some can be adjusted by the user.
/proc/acpi/thermal_zone/
A separate subdirectory exists for every thermal zone. A thermal zone is an area
with similar thermal properties whose number and names are designated by the
hardware manufacturer. However, many of the possibilities offered by ACPI are
rarely implemented. Instead, the temperature control is handled conventionally by
the BIOS. The operating system is not given much opportunity to intervene, because
the life span of the hardware is at stake. Therefore, some of the files only have a
theoretical value.
/proc/acpi/thermal_zone/*/temperature
Current temperature of the thermal zone.
/proc/acpi/thermal_zone/*/state
The state indicates if everything is ok or if ACPI applies active or passive
cooling. In the case of ACPI-independent fan control, this state is always ok.
/proc/acpi/thermal_zone/*/cooling_mode
Select the cooling method controlled by ACPI. Choose from passive (less performance, economical) or active cooling mode (full performance, fan noise).
/proc/acpi/thermal_zone/*/trip_points
Enables the determination of temperature limits for triggering specific actions, like
passive or active cooling, suspension (hot), or a shutdown (critical). The
possible actions are defined in the DSDT (device-dependent). The trip points determined in the ACPI specification are critical, hot, passive, active1, and
active2. Even if not all of them are implemented, they must always be entered
in this file in this order. For example, the entry echo 90:0:70:0:0 >
trip_points sets the temperature for critical to 90 and the temperature for
passive to 70 (all temperatures measured in degrees Celsius).
/proc/acpi/thermal_zone/*/polling_frequency
If the value in temperature is not updated automatically when the temperature
changes, toggle the polling mode here. The command echo X >
/proc/acpi/thermal_zone/*/polling_frequency causes the temperature to be queried every X seconds. Set X=0 to disable polling.
Power Management
265
None of these settings, information, and events need to be edited manually. This can
be done with the Powersave daemon (powersaved) and various applications, like powersave, kpowersave, and wmpowersave. See Section 21.3.3, “ACPI Tools” (page 267).
Because powersaved covers the functionalities of the older acpid, acpid is no longer
needed.
21.3.2 Controlling the CPU Performance
The CPU can save energy in three ways. Depending on the operating mode of the
computer, these methods can be combined. Saving energy also means that the system
heats up less and the fans are activated less frequently.
Frequency and Voltage Scaling
PowerNow! and Speedstep are the designations AMD and Intel use for this technology. However, this technology is also applied in processors of other manufacturers.
The clock frequency of the CPU and its core voltage are reduced at the same time,
resulting in more than linear energy savings. This means that when the frequency
is halved (half performance), far less than half of the energy is consumed. This
technology is independent from APM or ACPI and requires a daemon that adapts
the frequency and the current need for performance. The settings can be made in
the directory /sys/devices/system/cpu/cpu*/cpufreq/.
Throttling the Clock Frequency
This technology omits a certain percentage of the clock signal impulses for the CPU.
At 25% throttling, every fourth impulse is omitted. At 87.5%, only every eighth
impulse reaches the processor. However, the energy savings are a little less than
linear. Normally, throttling is only used if frequency scaling is not available or to
maximize power savings. This technology, too, must be controlled by a special
process. The system interface is /proc/acpi/processor/*/throttling.
Putting the Processor to Sleep
The operating system puts the processor to sleep whenever there is nothing to do.
In this case, the operating system sends the CPU a halt command. There are three
states: C1, C2, and C3. In the most economic state, C3, even the synchronization
of the processor cache with the main memory is halted. Therefore, this state can
only be applied if no other device modifies the contents of the main memory via
bus master activity. Some drivers prevent the use of C3. The current state is displayed
in /proc/acpi/processor/*/power.
266
Frequency scaling and throttling are only relevant if the processor is busy, because the
most economic C state is applied anyway when the processor is idle. If the CPU is busy,
frequency scaling is the recommended power saving method. Often the processor only
works with a partial load. In this case, it can be run with a lower frequency. Usually,
dynamic frequency scaling controlled by a daemon, such as powersaved, is the best
approach. A static setting to a low frequency is useful for battery operation or if you
want the computer to be cool or quiet.
Throttling should be used as the last resort, for example, to extend the battery operation
time despite a high system load. However, some systems do not run smoothly when
they are throttled too much. Moreover, CPU throttling does not make sense if the CPU
has little to do.
In SUSE Linux these technologies are controlled by the powersave daemon. The configuration is explained in Section 21.5, “The powersave Package” (page 270).
21.3.3 ACPI Tools
The range of more or less comprehensive ACPI utilities includes tools that merely display
information, like the battery charge level and the temperature (acpi, klaptopdaemon,
wmacpimon, etc.), tools that facilitate the access to the structures in /proc/acpi or
that assist in monitoring changes (akpi, acpiw, gtkacpiw), and tools for editing the ACPI
tables in the BIOS (package pmtools).
21.3.4 Troubleshooting
There are two different types of problems. On one hand, the ACPI code of the kernel
may contain bugs that were not detected in time. In this case, a solution will be made
available for download. More often, however, the problems are caused by the BIOS.
Sometimes, deviations from the ACPI specification are purposely integrated in the
BIOS to circumvent errors in the ACPI implementation in other widespread operating
systems. Hardware components that have serious errors in the ACPI implementation
are recorded in a blacklist that prevents the Linux kernel from using ACPI for these
components.
The first thing to do when problems are encountered is to update the BIOS. If the
computer does not boot at all, one of the following boot parameters may be helpful:
Power Management
267
pci=noacpi
Do not use ACPI for configuring the PCI devices.
acpi=oldboot
Only perform a simple resource configuration. Do not use ACPI for other purposes.
acpi=off
Disable ACPI.
WARNING: Problems Booting without ACPI
Some newer machines (especially SMP systems and AMD64 systems) need ACPI
for configuring the hardware correctly. On these machines, disabling ACPI can
cause problems.
Monitor the boot messages of the system with the command dmesg | grep -2i
acpi (or all messages, because the problem may not be caused by ACPI) after booting.
If an error occurs while parsing an ACPI table, the most important table—the DSDT—can be replaced with an improved version. In this case, the faulty DSDT of the
BIOS is ignored. The procedure is described in Section 21.5.4, “Troubleshooting”
(page 276).
In the kernel configuration, there is a switch for activating ACPI debug messages. If a
kernel with ACPI debugging is compiled and installed, experts searching for an error
can be supported with detailed information.
If you experience BIOS or hardware problems, it is always advisable to contact the
manufacturers. Especially if they do not always provide assistance for Linux, they
should be confronted with the problems. Manufacturers will only take the issue seriously
if they realize that an adequate number of their customers use Linux.
For More Information
Additional documentation and help on ACPI:
• http://www.cpqlinux.com/acpi-howto.html (detailed ACPI HOWTO,
contains DSDT patches)
• http://www.intel.com/technology/iapc/acpi/faq.htm (ACPI
FAQ @Intel)
268
• http://acpi.sourceforge.net/ (the ACPI4Linux project at Sourceforge)
• http://www.poupinou.org/acpi/ (DSDT patches by Bruno Ducrot)
21.4
Rest for the Hard Disk
In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in
a more economic or quieter mode. On modern laptops, you do not need to switch off
the hard disks manually, because they automatically enter an economic operating mode
whenever they are not needed. However, if you want to maximize power savings, test
some of the following methods. Most of the functions can be controlled with powersaved
and the YaST power management module, which is discussed in further detail in Section 21.6, “The YaST Power Management Module” (page 278).
The hdparm application can be used to modify various hard disk settings. The option
-y instantly switches the hard disk to the standby mode. -Y puts it to sleep. hdparm
-S x causes the hard disk to be spun down after a certain period of inactivity. Replace
x as follows: 0 disables this mechanism, causing the hard disk to run continuously.
Values from 1 to 240 are multiplied by 5 seconds. Values from 241 to 251 correspond
to 1 to 11 times 30 minutes.
Internal power saving options of the hard disk can be controlled with the option -B.
Select a value from 0 to 255 for maximum saving to maximum throughput. The result
depends on the hard disk used and is difficult to assess. To make a hard disk quieter,
use the option -M. Select a value from 128 to 254 for quiet to fast.
Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write
to the hard disk, waking it up repeatedly. Therefore, it is important to understand how
Linux handles data that needs to be written to the hard disk. First, all data is buffered
in the RAM. This buffer is monitored by the kernel update daemon (kupdated). When
the data reaches a certain age limit or when the buffer is filled to a certain degree, the
buffer content is flushed to the hard disk. The buffer size is dynamic and depends on
the size of the memory and the system load. By default, kupdated is set to short intervals
to achieve maximum data integrity. It checks the buffer every 5 seconds and notifies
the bdflush daemon when data is older than 30 seconds or the buffer reaches a fill level
of 30%. The bdflush daemon then writes the data to the hard disk. It also writes independently from kupdated if, for instance, the buffer is full.
Power Management
269
WARNING: Impairment of the Data Integrity
Changes to the kernel update daemon settings endanger the data integrity.
Apart from these processes, journaling file systems, like ReiserFS and Ext3, write their
metadata independently from bdflush, which also prevents the hard disk from spinning
down. To avoid this, a special kernel extension has been developed for mobile devices.
See /usr/src/linux/Documentation/laptop-mode.txt for details.
Another important factor is the way active programs behave. For example, good editors
regularly write hidden backups of the currently modified file to the hard disk, causing
the disk to wake up. Features like this can be disabled at the expense of data integrity.
In this connection, the mail daemon postfix makes use of the variable
POSTFIX_LAPTOP. If this variable is set to yes, postfix accesses the hard disk far
less frequently. However, this is irrelevant if the interval for kupdated was increased.
21.5
The powersave Package
The powersave package is responsible for the power saving function in laptops during
battery operation. Some of its features are also useful for normal workstations and
servers, such as suspend, standby, ACPI button functionality, and putting IDE hard
disks to sleep.
This package contains all power management features of your computer. It supports
hardware using ACPI, APM, IDE hard disks, and PowerNow! or SpeedStep technologies.
The functionalities from the packages apmd, acpid, ospmd, and cpufreqd (now
cpuspeed) have been consolidated in the powersave package. Daemons from these
packages should not be run concurrently with the powersave daemon.
Even if your system does not contain all the hardware elements listed above, use the
powersave daemon for controlling the power saving function. Because ACPI and APM
are mutually exclusive, you can only use one of these systems on your computer. The
daemon automatically detects any changes in the hardware configuration.
270
21.5.1 Configuring the powersave Package
Normally, the configuration of powersave is distributed to several files:
/etc/sysconfig/powersave/common
This file contains general settings for the powersave daemon. For example, the
amount of debug messages in /var/log/messages can be increased by increasing the value of the variable DEBUG.
/etc/sysconfig/powersave/events
The powersave daemon needs this file for processing system events. An event can
be assigned external actions or actions performed by the daemon itself. For external
actions, the daemon tries to run an executable file in /usr/lib/powersave/
scripts/. Predefined internal actions:
• ignore
• throttle
• dethrottle
• suspend_to_disk
• suspend_to_ram
• standby
• do_suspend_to_disk
• do_suspend_to_ram
• do_standby
throttle slows down the processor by the value defined in MAX_THROTTLING.
This value depends on the current scheme. dethrottle sets the processor to full
performance. suspend_to_disk, suspend_to_ram, and standby trigger
the system event for a sleep mode. These three actions are generally responsible for
triggering the sleep mode, but they should always be associated with specific system
events.
Power Management
271
The directory /usr/lib/powersave/scripts contains scripts for processing
events:
notify
Notification about an event by way of the console, X window, or acoustic signal.
screen_saver
Activates the screen saver.
switch_vt
Useful if the screen is displaced after a suspend or standby.
wm_logout
Saves the settings and logs out from GNOME, KDE, or other window managers.
wm_shutdown
Saves the GNOME or KDE settings and shuts down the system.
If, for example, the variable
EVENT_GLOBAL_SUSPEND2DISK="prepare_suspend_to_disk
do_suspend_to_disk" is set, the two scripts or actions are processed in the
specified order as soon as the user gives powersaved the command for the sleep
mode suspend to disk. The daemon runs the external script /usr/lib/
powersave/scripts/prepare_suspend_to_disk. After this script has
been processed successfully, the daemon runs the internal action
do_suspend_to_disk and sets the computer to the sleep mode after the script
has unloaded critical modules and stopped services.
The actions for the event of a sleep button could be modified as in
EVENT_BUTTON_SLEEP="notify suspend_to_disk". In this case, the
user is informed about the suspend by the external script notify. Subsequently,
the event EVENT_GLOBAL_SUSPEND2DISK is generated, resulting in the execution of the mentioned actions and a secure system suspend mode. The script notify
can be customized using the variable NOTIFY_METHOD in /etc/sysconfig/
powersave/common.
/etc/sysconfig/powersave/cpufreq
Contains variables for optimizing the dynamic CPU frequency settings.
/etc/sysconfig/powersave/battery
Contains battery limits and other battery-specific settings.
272
/etc/sysconfig/powersave/sleep
In this file, activate the sleep modes and determine which critical modules should
be unloaded and which services should be stopped prior to a suspend or standby
event. When the system is resumed, these modules are reloaded and the services
are restarted. You can even delay a triggered sleep mode, for example, to save files.
The default settings mainly concern USB and PCMCIA modules. A failure of suspend or standby is usually caused by certain modules. See Section 21.5.4, “Troubleshooting” (page 276) for more information about identifying the error.
/etc/sysconfig/powersave/thermal
Activates cooling and thermal control. Details about this subject are available in
the file /usr/share/doc/packages/powersave/README.thermal.
/etc/sysconfig/powersave/scheme_*
These are the various schemes that adapt the power consumption to certain deployment scenarios. A number of schemes are preconfigured and can be used as they
are. Custom schemes can be saved here.
21.5.2 Configuring APM and ACPI
Suspend and Standby
By default, the sleep modes are inactive, because they still do not work on some computers. There are three basic ACPI sleep modes and two APM sleep modes:
Suspend to Disk (ACPI S4, APM suspend)
Saves the entire memory content to the hard disk. The computer is switched off
completely and does not consume any power.
Suspend to RAM (ACPI S3, APM suspend)
Saves the states of all devices to the main memory. Only the main memory continues
consuming power.
Standby (ACPI S1, APM standby)
Switches some devices off (manufacturer-dependent).
Make sure that the following default options are set in the file /etc/sysconfig/
powersave/events for the correct processing of suspend, standby, and resume
(default settings following the installation of SUSE Linux):
Power Management
273
EVENT_GLOBAL_SUSPEND2DISK=
"prepare_suspend_to_disk do_suspend_to_disk"
EVENT_GLOBAL_SUSPEND2RAM=
"prepare_suspend_to_ram do_suspend_to_ram"
EVENT_GLOBAL_STANDBY=
"prepare_standby do_standby"
EVENT_GLOBAL_RESUME_SUSPEND2DISK=
"restore_after_suspend_to_disk"
EVENT_GLOBAL_RESUME_SUSPEND2RAM=
"restore_after_suspend_to_ram"
EVENT_GLOBAL_RESUME_STANDBY=
"restore_after_standby"
Custom Battery States
In the file /etc/sysconfig/powersave/battery, define three battery charge
levels (in percent) that trigger system alerts or specific actions when they are reached.
BATTERY_WARNING=20
BATTERY_LOW=10
BATTERY_CRITICAL=5
The actions or scripts to execute when the charge levels drop under the specified limits
are defined in the configuration file /etc/sysconfig/powersave/events.
The standard actions for buttons can be modified as described in Section 21.5.1,
“Configuring the powersave Package” (page 271).
EVENT_BATTERY_NORMAL="ignore"
EVENT_BATTERY_WARNING="notify"
EVENT_BATTERY_LOW="notify"
EVENT_BATTERY_CRITICAL="wm_shutdown"
Adapting Power Consumption to Various Conditions
The system behavior can be adapted to the type of power supply. The power consumption
of the system should be reduced when the system is disconnected from the AC power
supply and operated with the battery. Similarly, the performance should automatically
increase as soon as the system is connected to the AC power supply. The CPU frequency,
the power saving function of IDE, and a number of other parameters can be modified.
The actions to execute when the computer is disconnected from or connected to the AC
power supply are defined in /etc/sysconfig/powersave/events. Select the
schemes to use in /etc/sysconfig/powersave/common:
AC_SCHEME="performance"
BATTERY_SCHEME="powersave"
274
The schemes are stored in files in /etc/sysconfig/powersave. The filenames
are in the format scheme_name-of-the-scheme. The example refers to two
schemes: scheme_performance and scheme_powersave. performance,
powersave, presentation, and acoustic are preconfigured. Existing schemes
can be edited, created, deleted, or associated with different power supply states with
the help of the YaST power management module described in Section 21.6, “The YaST
Power Management Module” (page 278).
21.5.3 Additional ACPI Features
If you use ACPI, you can control the response of your system to ACPI buttons (power,
sleep, lid open, and lid closed). Configure execution of the actions in /etc/
sysconfig/powersave/events. Refer to this configuration file for an explanation
of the individual options.
EVENT_BUTTON_POWER="wm_shutdown"
When the power button is pressed, the system responds by shutting down the respective window manager (KDE, GNOME, fvwm, etc.).
EVENT_BUTTON_SLEEP="suspend_to_disk"
When the sleep button is pressed, the system is set to the suspend-to-disk mode.
EVENT_BUTTON_LID_OPEN="ignore"
Nothing happens when the lid is opened.
EVENT_BUTTON_LID_CLOSED="screen_saver"
When the lid is closed, the screen saver is activated.
Further throttling of the CPU performance is possible if the CPU load does not exceed
a specified limit for a specified time. Specify the load limit in
PROCESSOR_IDLE_LIMIT and the time-out in CPU_IDLE_TIMEOUT. If the CPU
load stays below the limit longer than the time-out, the event configured in
EVENT_PROCESSOR_IDLE is activated. If the CPU is busy again,
EVENT_PROCESSOR_BUSY is executed.
Power Management
275
21.5.4 Troubleshooting
All error messages and alerts are logged in the file /var/log/messages. If you
cannot find the needed information, increase the verbosity of the messages of powersave
using DEBUG in the file /etc/sysconfig/powersave/common. Increase the
value of the variable to 7 or even 15 and restart the daemon. The more detailed error
messages in /var/log/messages should help you to find the error. The following
sections cover the most common problems with powersave.
ACPI Activated with Hardware Support but Functions
Do Not Work
If you experience problems with ACPI, use the command dmesg|grep -i acpi
to search the output of dmesg for ACPI-specific messages. A BIOS update may be
required to resolve the problem. Go to the home page of your laptop manufacturer, look
for an updated BIOS version, and install it. Ask the manufacturer to comply with the
latest ACPI specification. If the errors persist after the BIOS update, proceed as follows
to replace the faulty DSDT table in your BIOS with an updated DSDT:
1 Download the DSDT for your system from http://acpi.sourceforge
.net/dsdt/tables. Check if the file is decompressed and compiled as shown
by the file extension .aml (ACPI machine language). If this is the case, continue
with step 3.
2 If the file extension of the downloaded table is .asl (ACPI source language),
compile it with iasl (package pmtools). Enter the command iasl -sa
file.asl. The latest version of iasl (Intel ACPI compiler) is available at
http://developer.intel.com/technology/iapc/acpi/
downloads.htm.
3 Copy the file DSDT.aml to any location (/etc/DSDT.aml is recommended).
Edit /etc/sysconfig/kernel and adapt the path to the DSDT file accordingly. Start mkinitrd (package mkinitrd). Whenever you install the kernel
and use mkinitrd to create an initrd, the modified DSDT is integrated and
loaded when the system is booted.
276
CPU Frequency Does Not Work
Refer to the kernel sources (kernel-source) to see if your processor is supported.
You may need a special kernel module or module option to activate CPU frequency
control. This information is available in /usr/src/linux/Documentation/
cpu-freq/*. If a special module or module option is needed, configure it in the file
/etc/sysconfig/powersave/cpufreq by means of the variables
CPUFREQD_MODULE and CPUFREQD_MODULE_OPTS.
Suspend and Standby Do Not Work
There are several kernel-related problems that prevent the use of suspend and standby
on ACPI systems:
• Currently, systems with more than 1 GB RAM do not support suspend.
• Currently, multiprocessor systems and systems with a P4 processor (with hyperthreading) do not support suspend.
The error may also be due to a faulty DSDT implementation (BIOS). If this is the case,
install a new DSDT.
On ACPI and APM systems: When the system tries to unload faulty modules, the system
is arrested or the suspend event is not triggered. The same can also happen if you do
not unload modules or stop services that prevent a successful suspend. In both cases,
try to identify the faulty module that prevented the sleep mode. The log files generated
by the powersave daemon in /var/log/suspend2ram.log and /var/log/
suspend2disk.log are very helpful in this regard. If the computer does not enter
the sleep mode, the cause lies in the last module unloaded. Manipulate the following
settings in /etc/sysconfig/powersave/sleep to unload problematic modules
prior to a suspend or standby.
UNLOAD_MODULES_BEFORE_SUSPEND2DISK=""
UNLOAD_MODULES_BEFORE_SUSPEND2RAM=""
UNLOAD_MODULES_BEFORE_STANDBY=""
SUSPEND2DISK_RESTART_SERVICES=""
SUSPEND2RAM_RESTART_SERVICES=""
STANDBY_RESTART_SERVICES=""
If you use suspend or standby in changing network environments or in connection with
remotely mounted file systems, such as Samba and NIS, use automounter to mount
Power Management
277
them or add the respective services, for example, smbfs or nfs, in the above-mentioned
variable. If an application accesses the remotely mounted file system prior to a suspend
or standby, the service cannot be stopped correctly and the file system cannot be unmounted properly. After resuming the system, the file system may be corrupt and must
be remounted.
Using ACPI, Powersave Does Not Notice Battery
Limits
With ACPI, the operating system can request the BIOS to send a message when the
battery charge level drops under a certain limit. The advantage of this method is that
the battery state does not need to be polled constantly, which would impair the performance of the computer. However, this notification may not take place when the charge
level drops under the specified limit, even though the BIOS supposedly supports this
feature. If this happens on your system, set the variable FORCE_BATTERY_POLLING
in the file /etc/sysconfig/powersave/battery to yes to force battery
polling.
21.5.5 For More Information
Information about the powersave package is also available in /usr/share/doc/
packages/powersave.
21.6
The YaST Power Management
Module
The YaST power management module can configure all power management settings
already described. When started from the YaST Control Center with System → Power
Management, the first dialog of the module opens. It is shown in Figure 21.1, “Scheme
Selection” (page 279).
278
Figure 21.1
Scheme Selection
In this dialog, select the schemes to use for battery operation and AC operation. To add
or modify the schemes, click Edit Schemes, which opens an overview of the existing
schemes like that shown in Figure 21.2, “Overview of Existing Schemes” (page 279).
Figure 21.2
Overview of Existing Schemes
Power Management
279
In the scheme overview, select the scheme to modify then click Edit. To create a new
scheme, click Add. The dialog that opens is the same in both cases and is shown in
Figure 21.3, “Configuring a Scheme” (page 280).
Figure 21.3
Configuring a Scheme
First, enter a suitable name and description for the new or edited scheme. Determine if
and how the CPU performance should be controlled for this scheme. Decide if and to
what extent frequency scaling and throttling should be used. In the following dialog
for the hard disk, define a Standby Policy for maximum performance or for energy
saving. The Acoustic Policy controls the noise level of the hard disk (supported by few
hard disks). The Cooling Policy determines the cooling method to use. Unfortunately,
this type of thermal control is rarely supported by the BIOS. Read /usr/share/
doc/packages/powersave/README.thermal to learn how you can use the
fan and passive cooling methods.
Global power management settings can also be made from the initial dialog using Battery
Warnings, ACPI Settings, or Enable Suspend. Click Battery Warnings to access the
dialog for the battery charge level, shown in Figure 21.4, “Battery Charge Level”
(page 281).
280
Figure 21.4
Battery Charge Level
The BIOS of your system notifies the operating system whenever the charge level drops
under certain configurable limits. In this dialog, define three limits: Warning Capacity,
Low Capacity, and Critical Capacity. Specific actions are triggered when the charge
level drops under these limits. Usually, the first two states merely trigger a notification
to the user. The third critical level triggers a shutdown, because the remaining energy
is not sufficient for continued system operation. Select suitable charge levels and the
desired actions then click OK to return to the start dialog.
Power Management
281
Figure 21.5
ACPI Settings
Access the dialog for configuring the ACPI buttons using ACPI Settings. It is shown
in Figure 21.5, “ACPI Settings” (page 282). The settings for the ACPI buttons determine
how the system should respond to certain switches. Configure the system response to
pressing the power button, pressing the sleep button, and closing the laptop lid. Click
OK to complete the configuration and return to the start dialog.
Click Enable Suspend to enter a dialog in which to determine if and how users of this
system may use the suspend or standby functionality. Click OK to return to the main
dialog. Click OK again to exit the module and confirm your power management settings.
282
22
Wireless Communication
There are several possibilities for using your Linux system to communicate with other
computers, cellular phones, or peripheral devices. WLAN (wireless LAN) can be used
to network laptops. Bluetooth can be used to connect individual system components
(mouse, keyboard), peripheral devices, cellular phones, PDAs, and individual computers
with each other. IrDA is mostly used for communication with PDAs or cellular phones.
This chapter introduces all three technologies and their configuration.
22.1
Wireless LAN
Wireless LANs have become an indispensable aspect of mobile computing. Today,
most laptops have built-in WLAN cards. The 802.11 standard for the wireless communication of WLAN cards was prepared by the IEEE organization. Originally, this standard provided for a maximum transmission rate of 2 MBit/s. Meanwhile, several supplements have been added to increase the data rate. These supplements define details
such as the modulation, transmission output, and transmission rates:
Table 22.1
Overview of Various WLAN Standards
Name
Band (GHz)
Maximum Trans- Note
mission Rate
(MBit/s)
802.11
2.4
2
Outdated; virtually no end
devices available
Wireless Communication
283
Name
Band (GHz)
Maximum Trans- Note
mission Rate
(MBit/s)
802.11b
2.4
11
Widespread
802.11a
5
54
Less common
802.11g
2.4
54
Backward-compatible with
11b
Additionally, there are proprietary standards, like the 802.11b variation of Texas Instruments with a maximum transmission rate of 22 MBit/s (sometimes referred to as
802.11b+). However, the popularity of cards using this standard is limited.
22.1.1 Hardware
802.11 cards are not supported by SUSE Linux. Most cards using 802.11a, 802.11b,
and 802.11g are supported. New cards usually comply with the 802.11g standard, but
cards using 802.11b are still available. Normally, cards with the following chips are
supported:
• Aironet 4500, 4800
• Atheros 5210, 5211, 5212
• Atmel at76c502, at76c503, at76c504, at76c506
• Intel PRO/Wireless 2100, 2200BG, 2915ABG
• Intersil Prism2/2.5/3
• Intersil PrismGT
• Lucent/Agere Hermes
• Ralink RT2400, RT2500
• Texas Instruments ACX100, ACX111
284
• ZyDAS zd1201
A number of older cards that are rarely used and no longer available are also supported.
An extensive list of WLAN cards and the chips they use is available at the Web site of
AbsoluteValue Systems at http://www.linux-wlan.org/docs/wlan
_adapters.html.gz. http://wiki.uni-konstanz.de/wiki/bin/
view/Wireless/ListeChipsatz provides an overview of the various WLAN
chips.
Some cards need a firmware image that must be loaded into the card when the driver
is initialized. This is the case with Intersil PrismGT, Atmel, and TI ACX100 and
ACX111. The firmware can easily be installed with the YaST Online Update. The
firmware for Intel PRO/Wireless cards ships with SUSE Linux and is automatically
installed by YaST as soon as a card of this type is detected. More information about
this subject is available in the installed system in /usr/share/doc/packages/
wireless-tools/README.firmware.
Cards without native Linux support can be used by running the ndiswrapper application.
ndiswrapper uses the Windows drivers that are shipped together with most WLAN
cards. A description of ndiswrapper can be found under /usr/share/doc/
packages/ndiswrapper/README.SUSE when the package ndiswrapper is
installed. For in-depth information about ndiswrapper, refer to the project's Web site
at http://ndiswrapper.sourceforge.net/support.html.
22.1.2 Function
In wireless networking, various techniques and configurations are used to ensure fast,
high-quality, and secure connections. Different operating types suit different setups. It
can be difficult to choose the right authentication method. The available encryption
methods have different advantages and pitfalls.
Operating Mode
Basically, wireless networks can be classified as managed networks and ad-hoc networks.
Managed networks have a managing element: the access point. In this mode (also referred to as infrastructure mode), all connections of the WLAN stations in the network
run over the access point, which may also serve as a connection to an ethernet. Ad-hoc
networks do not have an access point. The stations communicate directly with each
Wireless Communication
285
other. The transmission range and number of participating stations are greatly limited
in ad-hoc networks. Therefore, an access point is usually more efficient. It is even
possible to use a WLAN card as an access point. Most cards support this functionality.
Because a wireless network is much easier to intercept and compromise than a wired
network, the various standards include authentication and encryption methods. In the
original version of the IEEE 802.11 standard, these are described under the term WEP.
However, because WEP has proven to be insecure (see Section “Security” (page 292)),
the WLAN industry (joined under the name Wi-Fi Alliance) has defined a new extension
called WPA, which is supposed to eliminate the weaknesses of WEP. The later IEEE
802.11i standard (also referred to as WPA2, because WPA is based on a draft version
802.11i) includes WPA and some other authentication and encryption methods.
Authentication
To make sure that only authorized stations can connect, various authentication mechanisms are used in managed networks:
Open
An open system is a system that does not require authentication. Any station can
join the network. Nevertheless, WEP encryption (see Section “Encryption”
(page 287)) can be used.
Shared Key (according to IEEE 802.11)
In this procedure, the WEP key is used for the authentication. However, this procedure is not recommended, because it makes the WEP key more susceptible to attacks.
All an attacker needs to do is to listen long enough to the communication between
the station and the access point. During the authentication process, both sides exchange the same information, once in encrypted form and once in unencrypted form.
This makes it possible for the key to be reconstructed with suitable tools. Because
this method makes use of the WEP key for the authentication and for the encryption,
it does not enhance the security of the network. A station that has the correct WEP
key can authenticate, encrypt, and decrypt. A station that does not have the key
cannot decrypt received packets. Accordingly, it cannot communicate, regardless
of whether it had to authenticate itself.
WPA-PSK (according to IEEE 802.1x)
WPA-PSK (PSK stands for preshared key) works similarly to the Shared Key procedure. All participating stations as well as the access point need the same key. The
key is 256 bits in length and is usually entered as a passphrase. This system does
286
not need a complex key management like WPA-EAP and is more suitable for private
use. Therefore, WPA-PSK is sometimes referred to as WPA “Home”.
WPA-EAP (according to IEEE 802.1x)
Actually, WPA-EAP is not an authentication system but a protocol for transporting
authentication information. WPA-EAP is used to protect wireless networks in enterprises. In private networks, it is scarcely used. For this reason, WPA-EAP is sometimes referred to as WPA “Enterprise”.
WPA-EAP needs a Radius server to authenticate users. EAP offers three different
methods for connecting and authenticating to the server: TLS (Transport Layer Security), TTLS (Tunneled Transport Layer Security), and PEAP (Protected Extensible
Authentication Protocol). In a nutshell, these options work as follows:
EAP-TLS
TLS authentication relies on the mutual exchange of certificates both for server
and client. First, the server presents its certificate to the client where it is evaluated. If the certificate is considered valid, the client in turn presents its certificate
to the server. While TLS is secure, it requires a working certification management
infrastructure in your network. This infrastructure is rarely found in private
networks.
EAP-TTLS and PEAP
Both TTLS and PEAP are two-stage protocols. In the first stage, a secure is established and in the second one the client authentication data is exchanged. They
require far less certification management overhead than TLS, if any.
Encryption
There are various encryption methods to ensure that no unauthorized person can read
the data packets that are exchanged in a wireless network or gain access to the network:
WEP (defined in IEEE 802.11)
This standard makes use of the RC4 encryption algorithm, originally with a key
length of 40 bits, later also with 104 bits. Often, the length is declared as 64 bits or
128 bits, depending on whether the 24 bits of the initialization vector are included.
However, this standard has some weaknesses. Attacks against the keys generated
by this system may be successful. Nevertheless, it is better to use WEP than not
encrypt the network at all.
Wireless Communication
287
TKIP (defined in WPA/IEEE 802.11i)
This key management protocol defined in the WPA standard uses the same encryption algorithm as WEP, but eliminates its weakness. Because a new key is generated
for every data packet, attacks against these keys are in vain. TKIP is used together
with WPA-PSK.
CCMP (defined in IEEE 802.11i)
CCMP describes the key management. Usually, it is used in connection with WPAEAP, but it can also be used with WPA-PSK. The encryption takes place according
to AES and is stronger than the RC4 encryption of the WEP standard.
22.1.3 Configuration with YaST
To configure your wireless network card, start the YaST Network Card module. In
Network Address Setup, select the device type Wireless and click Next. In Wireless
Network Card Configuration, shown in Figure 22.1, “YaST: Configuring the Wireless
Network Card” (page 288), make the basic settings for the WLAN operation:
Figure 22.1
YaST: Configuring the Wireless Network Card
Operating Mode
A station can be integrated in a WLAN in three different modes. The suitable mode
depends on the network in which to communicate: Ad-hoc (peer-to-peer network
288
without access point), Managed (network is managed by an access point), or Master
(your network card should be used as the access point). To use any of the WPAPSK or WPA-EAP modes, the operating mode must be set to managed.
Network Name (ESSID)
All stations in a wireless network need the same ESSID for communicating with
each other. If nothing is specified, the card automatically selects an access point,
which may not be the one you intended to use.
Authentication Mode
Select a suitable authentication method for your network: Open, Shared Key, WPAPSK, or WPA-EAP. If you select WPA authentication, a network name must be set.
Expert Settings
This button opens a dialog for the detailed configuration of your WLAN connection.
A detailed description of this dialog is provided later.
After completing the basic settings, your station is ready for deployment in the WLAN.
IMPORTANT: Security in Wireless Networks
Be sure to use one of the supported authentication and encryption methods
to protect your network traffic. Unencrypted WLAN connections allow third
parties to intercept all network data. Even a weak encryption (WEP) is better
than none at all. Refer to Section “Encryption” (page 287) and Section “Security”
(page 292) for information.
Depending on the selected authentication method, YaST prompts you to fine-tune the
settings in another dialog. For Open, there is nothing to configure, because this setting
implements unencrypted operation without authentication.
WEP Keys
Set a key input type. Choose from Passphrase, ASCII, or Hexadecimal. You may
keep up to four different keys to encrypt the transmitted data. Click Multiple Keys
to enter the key configuration dialog. Set the length of the key: 128 bit or 64 bit.
The default setting is 128 bit. In the list area at the bottom of the dialog, up to four
different keys can be specified for your station to use for the encryption. Press Set
as Default to define one of them as the default key. Unless you change this, YaST
uses the first entered key as the default key. If the standard key is deleted, one of
the other keys must be marked manually as the default key. Click Edit to modify
Wireless Communication
289
existing list entries or create new keys. In this case, a pop-up window prompts you
to select an input type (Passphrase, ASCII, or Hexadecimal). If you select
Passphrase, enter a word or a character string from which a key is generated according to the length previously specified. ASCII requests an input of 5 characters for a
64-bit key and 13 characters for a 128-bit key. For Hexadecimal, enter 10 characters
for a 64-bit key or 26 characters for a 128-bit key in hexadecimal notation.
WPA-PSK
To enter a key for WPA-PSK, select the input method Passphrase or Hexadecimal.
In the Passphrase mode, the input must be 8 to 63 characters. In the Hexadecimal
mode, enter 64 characters.
WPA-EAP
Enter the credentials you have been given by your network administrator. For TLS,
provide the Client Certificate and Server Certificate. TTLS and PEAP require
Identity and Password. Server Certificate is optional. YaST searches for any certificate under /etc/cert, so save the certificates given to you to this location and
restrict access to these files to 0600 (owner read and write).
Click Expert Settings to leave the dialog for the basic configuration of the WLAN
connection and enter the expert configuration. The following options are available in
this dialog:
Channel
The specification of a channel on which the WLAN station should work is only
needed in Ad-hoc and Master modes. In Managed mode, the card automatically
searches the available channels for access points. In Ad-hoc mode, select one of the
12 offered channels for the communication of your station with the other stations.
In Master mode, determine on which channel your card should offer access point
functionality. The default setting for this option is Auto.
Bit Rate
Depending on the performance of your network, you may want to set a certain bit
rate for the transmission from one point to another. In the default setting Auto, the
system tries to use the highest possible data transmission rate. Some WLAN cards
do not support the setting of bit rates.
Access Point
In an environment with several access points, one of them can be preselected by
specifying the MAC address.
290
Use Power Management
When you are on the road, use power saving technologies to maximize the operating
time of your battery. More information about power management is available in
Chapter 21, Power Management (page 259).
22.1.4 Utilities
hostap (package hostap) is used to run a WLAN card as an access point. More information about this package is available at the project home page (http://hostap
.epitest.fi/).
kismet (package kismet) is a network diagnosis tool with which to listen to the WLAN
packet traffic. In this way, you can also detect any intrusion attempts in your network.
More information is available at http://www.kismetwireless.net/ and in
the manual page.
22.1.5 Tips and Tricks for Setting Up a
WLAN
These tips can help tweak speed and stability as well as security aspects of your WLAN.
Stability and Speed
The performance and reliability of a wireless network mainly depend on whether the
participating stations receive a clean signal from the other stations. Obstructions like
walls greatly weaken the signal. The more the signal strength sinks, the more the
transmission slows down. During operation, check the signal strength with the iwconfig
utility on the command line (Link Quality field) or with KInternet in KDE. If you
have problems with the signal quality, try to set up the devices somewhere else or adjust
the position of the antennas of your access points. Auxiliary antennas that substantially
improve the reception are available for a number of PCMCIA WLAN cards. The rate
specified by the manufacturer, such as 54 MBit/s, is a nominal value that represents
the theoretical maximum. In practice, the maximum data throughput is no more than
half this value.
Wireless Communication
291
Security
If you want to set up a wireless network, remember that anybody within the transmission
range can easily access it if no security measures are implemented. Therefore, be sure
to activate an encryption method. All WLAN cards and access points support WEP
encryption. Although this is not entirely safe, it does present an obstacle for a potential
attacker. WEP is usually adequate for private use. WPA-PSK would be even better, but
it is not implemented in older access points or routers with WLAN functionality. On
some devices, WPA can be implemented by means of a firmware update. Furthermore,
Linux does not support WPA on all hardware components. When this documentation
was prepared, WPA only worked with cards using Atheros, Intel PRO/Wireless, or
Prism2/2.5/3 chips. On Prism2/2.5/3, WPA only works if the hostap driver is used (see
Section “Problems with Prism2 Cards” (page 292)). If WPA is not available, WEP is
better than no encryption. In enterprises with advanced security requirements, wireless
networks should only be operated with WPA.
22.1.6 Troubleshooting
If your WLAN card fails to respond, check if you have downloaded the needed firmware.
Refer to Section 22.1.1, “Hardware” (page 284). The following paragraphs cover some
known problems.
Multiple Network Devices
Modern laptops usually have a network card and a WLAN card. If you configured both
devices with DHCP (automatic address assignment), you may encounter problems with
the name resolution and the default gateway. This is evident from the fact that you can
ping the router but cannot surf the Internet. The Support Database at http://portal
.suse.com features an article on this subject. To find the article, enter “DHCP” in
the search dialog.
Problems with Prism2 Cards
Several drivers are available for devices with Prism2 chips. The various cards work
more or less smoothly with the various drivers. With these cards, WPA is only possible
with the hostap driver. If such a card does not work properly or not at all or you want
292
to use WPA, read /usr/share/doc/packages/wireless-tools/README
.prism2.
WPA
WPA support is quite new in SUSE Linux and still under development. Thus, YaST
does not support the configuration of all WPA authentication methods. Not all wireless
LAN cards and drivers support WPA. Some cards need a firmware update to enable
WPA. If you want to use WPA, read /usr/share/doc/packages/
wireless-tools/README.wpa.
22.1.7 For More Information
The Internet pages of Jean Tourrilhes, who developed the Wireless Tools for Linux,
present a wealth of useful information about wireless networks. See http://www
.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html.
22.2
Bluetooth
Bluetooth is a wireless technology for connecting various devices, such as cellular
phones, PDAs, peripheral devices, laptops, or system components like the keyboard or
mouse. The name is derived from the Danish king Harold Bluetooth, who united various
warring factions in Scandinavia. The Bluetooth logo is based on the runes for “H” (resembles a star) and “B”.
A number of important aspects distinguish Bluetooth from IrDA. First, the individual
devices do not need to “see” each other directly and, second, several devices can be
connected in a network. However, the maximum data rate is 720 Kbps (in the current
version 1.2). Theoretically, Bluetooth can even communicate through walls. In practice,
however, this depends on the properties of the wall and the device class. There are three
device classes with transmission ranges between ten and a hundred meters.
Wireless Communication
293
22.2.1 Basics
The following sections outline the basic principles of how Bluetooth works. Learn
which software requirements need to be met, how Bluetooth interacts with your system,
and how Bluetooth profiles work.
Software
To be able to use Bluetooth, you need a Bluetooth adapter (either a built-in adapter or
an external device), drivers, and a Bluetooth protocol stack. The Linux kernel already
contains the basic drivers for using Bluetooth. The Bluez system is used as protocol
stack. To make sure that the applications work with Bluetooth, the base packages
bluez-libs and bluez-utils must be installed. These packages provide a
number of needed services and utilities. Additionally, some adapters, such as Broadcom
or AVM BlueFritz!, require the bluez-firmware package to be installed. The
bluez-cups package enables printing over Bluetooth connections.
General Interaction
A Bluetooth system consists of four interlocked layers that provide the desired functionality:
Hardware
The adapter and a suitable driver for support by the Linux kernel.
Configuration Files
Used for controlling the Bluetooth system.
Daemons
Services that are controlled by the configuration files and provide the functionality.
Applications
The applications allow the functionality provided by the daemons to be used and
controlled by the user.
When inserting a Bluetooth adapter, its driver is loaded by the hotplug system. After
the driver is loaded, the system checks the configuration files to see if Bluetooth should
be started. If this is the case, it determines the services to start. Based on this information,
the respective daemons are started. Bluetooth adapters are probed upon installation. If
294
one or more are found, Bluetooth is enabled. Otherwise the Bluetooth system is deactivated. Any Bluetooth device added later must be enabled manually.
Profiles
In Bluetooth, services are defined by means of profiles, such as the file transfer profile,
the basic printing profile, and the personal area network profile. To enable a device to
use the services of another device, both must understand the same profile—a piece of
information that is often missing in the device package and manual. Unfortunately,
some manufacturers do not comply strictly with the definitions of the individual profiles.
Despite this, communication between the devices usually works smoothly.
In the following text, local devices are those physically connected to the computer. All
other devices that can only be accessed over wireless connections are referred to as remote devices.
22.2.2 Configuration
This section introduces Bluetooth configuration. Learn which configuration files are
involved, which tools are needed, and how to configure Bluetooth with YaST or manually.
Configuring Bluetooth with YaST
Use the YaST Bluetooth module, shown in Figure 22.2, “YaST Bluetooth Configuration”
(page 296), to configure Bluetooth support on your system. As soon as hotplug detects
a Bluetooth adapter on your system (for example, during booting or when you plug in
an adapter), Bluetooth is automatically started with the settings configured in this
module.
Wireless Communication
295
Figure 22.2
YaST Bluetooth Configuration
In the first step of the configuration, determine whether Bluetooth services should be
started on your system. If you have enabled the Bluetooth services, two things can be
configured. First, the Device Name. This is the name other devices display when your
computer has been discovered. There are two placeholders available—%h stands for
the hostname of the system (useful, for example, if it is assigned dynamically by DHCP)
and %d inserts the interface number (only useful if you have more than one Bluetooth
adapter in your computer). For example, if you enter Laptop %h in the field and
DHCP assigns the name unit123 to your computer, other remote devices would know
your computer as Laptop unit123.
The Security Manager parameter is related to the behavior of the local system when a
remote device tries to connect. The difference is in the handling of the PIN number.
Either allow any device to connect without a PIN or determine how the correct PIN is
chosen if one is needed. You can enter a PIN (stored in a configuration file) in the appropriate input field. If a device tries to connect, it first uses this PIN. If it fails, it falls
back to using no PIN. For maximum security, it is best to choose Always Ask User for
PIN. This option allows you to use different PINs for different (remote) devices.
Click Advanced Daemon Configuration to enter the dialog for selecting and configuring
the available services (called profiles in Bluetooth). All available services are displayed
in a list and can be enabled or disabled by clicking Activate or Deactivate. Click Edit
296
to open a dialog in which to specify additional arguments for the selected service
(daemon). Do not change anything unless you are familiar with the service. After
completing the configuration of the daemons, exit this dialog by clicking OK.
Back in the main dialog, click Security Options to enter the security dialog and specify
encryption, authentication, and scan settings. Then exit the security dialog to return to
the main dialog. After you close the main dialog with Finish, your Bluetooth system
is ready for use.
From the main dialog, you can reach the Device and Service Classes dialog, too.
Bluetooth devices are grouped into various device classes. In this dialog, choose the
correct one for your computer, such as Desktop or Laptop. The device class is not very
important, unlike the service class, also set here. Sometimes remote Bluetooth devices,
like cell phones, only allow certain functions if they can detect the correct service class
set on your system. This is often the case for cell phones that expect a class called Object
Transfer before they allow the transfer of files from or to the computer. You can choose
multiple classes. It is not useful to select all classes “just in case.” The default selection
should be appropriate in most cases.
To use Bluetooth to set up a network, activate PAND in the Advanced Daemon Configuration dialog and set the mode of the daemon with Edit. For a functional Bluetooth
network connection, one pand must operate in the Listen mode and the peer in the
Search mode. By default, the Listen mode is preset. Adapt the behavior of your local
pand. Additionally, configure the bnepX interface (X stands for the device number in
the system) in the YaST Network Card module.
Configuring Bluetooth Manually
The configuration files for the individual components of the Bluez system are located
in the directory /etc/bluetooth. The only exception is the file /etc/
sysconfig/bluetooth for starting the components, which is modified by the
YaST module.
The configuration files described below can only be modified by the user root. Currently, there is no graphical user interface to change all settings. The most important
ones can be set using the YaST Bluetooth module, described in Section “Configuring
Bluetooth with YaST” (page 295). All other settings are only of interest for experienced
users with special cases. Usually, the default settings should be adequate.
Wireless Communication
297
A PIN number provides basic protection against unwanted connections. Mobile phones
usually query the PIN when establishing the first contact (or when setting up a device
contact on the phone). For two devices to be able to communicate, both must identify
themselves with the same PIN. On the computer, the PIN is located in the file /etc/
bluetooth/pin.
IMPORTANT: Security of Bluetooth Connections
Despite the PINs, the transmission between two devices may not be fully secure.
By default, the authentication and encryption of Bluetooth connections is deactivated. Activating authentication and encryption may result in communication
problems with some Bluetooth devices.
Various settings, such as the device names and the security mode, can be changed in
the configuration file /etc/bluetooth/hcid.conf. Usually, the default settings
should be adequate. The file contains comments describing the options for the various
settings.
Two sections in the included file are designated as options and device. The first
contains general information that hcid uses for starting. The latter contains settings for
the individual local Bluetooth devices.
One of the most important settings of the options section is security auto;.
If set to auto, hcid tries to use the local PIN for incoming connections. If it fails, it
switches to none and establishes the connection anyway. For increased security, this
default setting should be set to user to make sure that the user is requested to enter a
PIN every time a connection is established.
Set the name under which the computer is displayed on the other side in the device
section. The device class, such as Desktop, Laptop, or Server, is defined in this
section. Authentication and encryption are also enabled or disabled here.
22.2.3 System Components and Utilities
The operability of Bluetooth depends on the interaction of various services. At least
two background daemons are needed: hcid (host controller interface daemon), which
serves as an interface for the Bluetooth device and controls it, and sdpd (service discovery protocol daemon), by means of which a device can find out which services the host
makes available. If they are not activated automatically when the system is started, both
298
hcid and sdpd can be activated with the command rcbluetooth start. This
command must be executed as root.
The following paragraphs briefly describe the most important shell tools that can be
used for working with Bluetooth. Although various graphical components are now
available for controlling Bluetooth, it can be worthwhile to check these programs.
Some of the commands can only be executed as root. This includes the command
l2ping device_address for testing the connection to a remote device.
hcitool
hcitool can be used to determine whether local and remote devices are detected. The
command hcitool dev lists the local devices. The output generates a line in the
form interface_name device_address for every detected local device.
Search for remote devices with the command hcitool inq. Three values are returned
for every detected device: the device address, the clock offset, and the device class.
The device address is important, because other commands use it for identifying the
target device. The clock offset mainly serves a technical purpose. The class specifies
the device type and the service type as a hexadecimal value.
The command hcitool name device-address can be used to determine the
device name of a remote device. In the case of a remote computer, the class and the
device name correspond to the information in its /etc/bluetooth/hcid.conf.
Local device addresses generate an error output.
hciconfig
The command /usr/sbin/hciconfig delivers further information about the local
device. If hciconfig is executed without any arguments, the output shows device
information, such as the device name (hciX), the physical device address (a 12-digit
number in the form 00:12:34:56:78), and information about the amount of transmitted data.
hciconfig hci0 name displays the name that is returned by your computer when
it receives requests from remote devices. As well as querying the settings of the local
device, hciconfig can be used for modifying these settings. For example,
hciconfig hci0 name TEST sets the name to TEST.
Wireless Communication
299
sdptool
The program sdptool can be used to check which services are made available by a
specific device. The command sdptool browse device_address returns all
services of a device. Use the command sdptool search service_code to
search for a specific service. This command scans all accessible devices for the requested
service. If one of the devices offers the service, the program prints the full service name
returned by the device together with a brief description. View a list of all possible service
codes by entering sdptool without any parameters.
22.2.4 Graphical Applications
In Konqueror, enter the URL bluetooth:/ to list local and remote Bluetooth devices.
Double-click a device for an overview of the services provided by the device. If you
move across one of the specified services with the mouse, the browser's status bar shows
which profile is used for the service. If you click a service, a dialog opens, asking what
to do: save, use the service (an application must be started to do this), or cancel the action. Mark a check box if you do not want the dialog to be displayed again but always
want the selected action to be performed. For some services, support is not yet available.
For others, additional packages may need to be installed.
22.2.5 Examples
This section features two typical examples of possible Bluetooth scenarios. The first
shows how a network connection between two hosts can be established via Bluetooth.
The second features a connection between a computer and a mobile phone.
Network Connection between Two Hosts
In the first example, a network connection is established between the hosts H1 and H2.
These two hosts have the Bluetooth device addresses baddr1 and baddr2 (determined
on both hosts with the command hcitool dev as described above). The hosts should
be identified with the IP addresses 192.168.1.3 (H1) and 192.168.1.4 (H2).
The Bluetooth connection is established with the help of pand (personal area networking
daemon). The following commands must be executed by the user root. The description
300
focuses on the Bluetooth-specific actions and does not provide a detailed explanation
of the network command ip.
Enter pand -s to start pand on the host H1. Subsequently, a connection can be established on the host H2 with pand -c baddr1. If you enter ip link show on one
of the hosts to list the available network interfaces, the output should contain an entry
like the following:
bnep0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
link/ether 00:12:34:56:89:90 brd ff:ff:ff:ff:ff:ff
Instead of 00:12:34:56:89:90, the output should contain the local device address
baddr1 or baddr2. Now this interface must be assigned an IP address and activated.
On H1, this can be done with the following two commands:
ip addr add 192.168.1.3/24 dev bnep0
ip link set bnep0 up
On H2:
ip addr add 192.168.1.4/24 dev bnep0
ip link set bnep0 up
Now H1 can be accessed from H2 under the IP 192.168.1.3. Use the command
ssh 192.168.1.4 to access H2 from H1, assuming H2 runs an sshd, which is activated by default in SUSE Linux. The command ssh 192.168.1.4 can also be run
as a normal user.
Data Transfer from a Mobile Phone to the Computer
The second example shows how to transfer a photograph created with a mobile phone
with a built-in digital camera to a computer (without incurring additional costs for the
transmission of a multimedia message). Although the menu structure may differ on
various mobile phones, the procedure is usually quite similar. Refer to the manual of
your phone, if necessary. This example describes the transfer of a photograph from a
Sony Ericsson mobile phone to a laptop. The service Obex-Push must be available on
the computer and the computer must grant the mobile phone access. In the first step,
the service is made available on the laptop. This is done by means of the opd daemon
from the package bluez-utils. Start the daemon with the following command:
opd --mode OBEX --channel 10 --daemonize --path /tmp --sdp
Wireless Communication
301
Two important parameters are used: --sdp registers the service with sdpd and --path
/tmp instructs the program where to save the received data—in this case to /tmp.
You can also specify any other directory to which you have write access.
Now the mobile phone must get to know the computer. To do this, open the Connect
menu on the phone and select Bluetooth. If necessary, click Turn On before selecting
My devices. Select New device and let your phone search for the laptop. If a device is
detected, its name appears in the display. Select the device associated with the laptop.
If you encounter a PIN query, enter the PIN specified in /etc/bluetooth/pin.
Now your phone recognizes the laptop and is able to exchange data with the laptop.
Exit the current menu and go to the image menu. Select the image to transfer and press
More. In the next menu, press Send to select a transmission mode. Select Via Bluetooth.
The laptop should be listed as a target device. Select the laptop to start the transmission.
The image is then saved to the directory specified with the opd command. Audio tracks
can be transferred to the laptop in the same way.
22.2.6 Troubleshooting
If you have difficulties establishing a connection, proceed according to the following
list. Remember that the error can be on either side of a connection or even on both sides.
If possible, reconstruct the problem with another Bluetooth device to verify that the
device is not defective.
Is the local device listed in the output of hcitool dev?
If the local device is not listed in this output, hcid is not started or the device is not
recognized as a Bluetooth device. This can have various causes. The device may
be defective or the correct driver may be missing. Laptops with built-in Bluetooth
often have an on and off switch for wireless devices, like WLAN and Bluetooth.
Check the manual of your laptop to see if your device has such a switch. Restart
the Bluetooth system with the command rcbluetooth restart and check if
any errors are reported in /var/log/messages.
Does your Bluetooth adapter need a firmware file?
If it does, install bluez-bluefw and restart the Bluetooth system with
rcbluetooth restart.
Does the output of hcitool inq return other devices?
Test this command more than once. The connection may have interferences, because
the frequency band of Bluetooth is also used by other devices.
302
Do the PINs match?
Check if the PIN number of the computer (in /etc/bluetooth/pin) matches
that of the target device.
Can the remote device “see” your computer?
Try to establish the connection from the remote device. Check if this device sees
the computer.
Can a network connection be established (see Section “Network Connection between
Two Hosts” (page 300))?
The setup described in Section “Network Connection between Two Hosts” (page 300)
may not work for several reasons. For example, one of the two computers may not
support the ssh protocol. Try ping 192.168.1.3 or ping 192.168.1.4.
If this works, check if sshd is active. Another problem could be that one of the two
devices already has network settings that conflict with the address 192.168.1.X
in the example. If this is the case, try different addresses, such as 10.123.1.2
and 10.123.1.3.
Does the laptop appear as a target device (see Section “Data Transfer from a
Mobile Phone to the Computer” (page 301))? Does the mobile device recognize the
Obex-Push service on the laptop?
In My devices, select the respective device and view the list of Services. If ObexPush is not displayed (even after the list is updated), the problem is caused by opd
on the laptop. Is opd active? Do you have write access to the specified directory?
Does the scenario described in Section “Data Transfer from a Mobile Phone to
the Computer” (page 301) work the other way around?
If the obexftp package is installed, the command obexftp -b
device_address -B 10 -p image can be used on some devices. Several
Siemens and Sony Ericsson models have been tested and found to be functional.
Refer to the documentation in /usr/share/doc/packages/obexftp.
22.2.7 For More Information
An extensive overview of various instructions for the use and configuration of Bluetooth
is available at http://www.holtmann.org/linux/bluetooth/. Other useful
information and instructions:
Wireless Communication
303
• Official howto of the Bluetooth protocol stack integrated in the kernel: http://
bluez.sourceforge.net/howto/index.html
• Connection to PalmOS PDA: http://www.cs.ucl.ac.uk/staff/s
.zachariadis/btpalmlinux.html
22.3
Infrared Data Transmission
IrDA (Infrared Data Association) is an industry standard for wireless communication
with infrared light. Many laptops sold today are equipped with an IrDA-compatible
transceiver that enables communication with other devices, such as printers, modems,
LANs, or other laptops. The transfer speed ranges from 2400 bps to 4 Mbps.
There are two IrDA operation modes. The standard mode, SIR, accesses the infrared
port through a serial interface. This mode works on almost all systems and is sufficient
for most requirements. The faster mode, FIR, requires a special driver for the IrDA
chip. Not all chip types are supported in FIR mode because of a lack of appropriate
drivers. Set the desired IrDA mode in the BIOS of your computer. The BIOS also shows
which serial interface is used in SIR mode.
Information about IrDA can be found in the IrDA how-to by Werner Heuser at http://
tuxmobil.org/Infrared-HOWTO/Infrared-HOWTO.html. Additionally
refer to the Web site of the Linux IrDA Project at http://irda.sourceforge
.net/.
22.3.1 Software
The necessary kernel modules are included in the kernel package. The package irda
provides the necessary helper applications for supporting the infrared interface. The
documentation can be found at /usr/share/doc/packages/irda/README
after the installation of the package.
22.3.2 Configuration
The IrDA system service is not started automatically when the system is booted. Use
the YaST IrDA module for the activation. Only one setting can be modified in this
304
module: the serial interface of the infrared device. The test window shows two outputs.
One is the output of irdadump, which logs all sent and received IrDA packets. This
output should contain the name of the computer and the names of all infrared devices
in transmission range. An example for these messages is shown in Section 22.3.4,
“Troubleshooting” (page 306). All devices to which an IrDA connection exists are listed
in the lower part of the window.
IrDA consumes a considerable amount of battery power, because a discovery packet
is sent every few seconds to detect other peripheral devices. Therefore, IrDA should
only be started when necessary if you depend on battery power. Enter the command
rcirda start to activate it or rcirda stop to deactivate it. All needed kernel
modules are loaded automatically when the interface is activated.
Manual configuration can be performed in the file /etc/sysconfig/irda. This
file contains only one variable, IRDA_PORT, which determines the interface to use in
SIR mode.
22.3.3 Usage
Data can be sent to the device file /dev/irlpt0 for printing. The device file /dev/
irlpt0 acts just like the normal /dev/lp0 cabled interface, except the printing data
is sent wirelessly with infrared light. For printing, make sure that the printer is in visual
range of the computer's infrared interface and the infrared support is started.
A printer that is operated over the infrared interface can be configured with the YaST
Printer module. Because it is not detected automatically, configure it manually by
clicking Other (not detected). In the following dialog, select IrDA printer. Usually,
irlpt0 is the right connection. Details about operating printers in Linux are available
in Chapter 31, Printer Operation (page 461).
Communication with other hosts and with mobile phones or other similar devices is
conducted through the device file /dev/ircomm0. The Siemens S25 and Nokia 6210
mobile phones, for example, can dial and connect to the Internet with the wvdial application using the infrared interface. Synchronizing data with a Palm Pilot is also possible,
provided the device setting of the corresponding application has been set to /dev/
ircomm0.
If you want, you can address only devices that support the printer or IrCOMM protocols.
Devices that support the IROBEX protocol, such as the 3Com Palm Pilot, can be ac-
Wireless Communication
305
cessed with special applications, like irobexpalm and irobexreceive. Refer to the IRHOWTO (http://tldp.org/HOWTO/Infrared-HOWTO/) for information.
The protocols supported by the device are listed in brackets after the name of the device
in the output of irdadump. IrLAN protocol support is still a “work in progress.”
22.3.4 Troubleshooting
If devices connected to the infrared port do not respond, use the command irdadump
(as root) to check if the other device is recognized by the computer. Something similar
to Example 22.1, “Output of irdadump” (page 306) appears regularly when a Canon
BJC-80 printer is in visible range of the computer:
Example 22.1
Output of irdadump
21:41:38.435239
21:41:38.525167
21:41:38.615159
21:41:38.705178
21:41:38.795198
21:41:38.885163
21:41:38.965133
xid:cmd
xid:cmd
xid:cmd
xid:cmd
xid:cmd
xid:cmd
xid:rsp
5b62bed5 > ffffffff S=6 s=0 (14)
5b62bed5 > ffffffff S=6 s=1 (14)
5b62bed5 > ffffffff S=6 s=2 (14)
5b62bed5 > ffffffff S=6 s=3 (14)
5b62bed5 > ffffffff S=6 s=4 (14)
5b62bed5 > ffffffff S=6 s=5 (14)
5b62bed5 < 6cac38dc S=6 s=5 BJC-80
hint=8804 [Printer IrCOMM ] (23)
21:41:38.975176 xid:cmd 5b62bed5 > ffffffff S=6 s=* earth
hint=0500 [ PnP Computer ] (21)
Check the configuration of the interface if there is no output or the other device does
not reply. Verify that the correct interface is used. The infrared interface is sometimes
located at /dev/ttyS2 or at /dev/ttyS3 and an interrupt other than IRQ 3 is
sometimes used. These settings can be checked and modified in the BIOS setup menu
of almost every laptop.
A simple video camera can also help in determining whether the infrared LED lights
up at all. Most video cameras can see infrared light; the human eye cannot.
306
Part VII Administration
23
Security in Linux
Masquerading and a firewall ensure a controlled data flow and data exchange. SSH
(secure shell) enables you to log in to remote hosts over an encrypted connection. The
encryption of files or entire partitions protects your data in the event that third parties
gain access to your system. Along with technical instructions, find information about
security aspects of Linux networks.
23.1
Masquerading and Firewalls
Whenever Linux is used in a networked environment, you can use the kernel functions
that allow the manipulation of network packets to maintain a separation between internal
and external network areas. The Linux netfilter framework provides the means to establish an effective firewall that keeps different networks apart. With the help of iptables—a
generic table structure for the definition of rule sets—precisely control the packets allowed to pass a network interface. Such a packet filter can be set up quite easily with
the help of SuSEfirewall2 and the corresponding YaST module.
23.1.1 Packet Filtering with iptables
The components netfilter and iptables are responsible for the filtering and manipulation
of network packets as well as for network address translation (NAT). The filtering criteria and any actions associated with them are stored in chains, which must be matched
one after another by individual network packets as they arrive. The chains to match are
stored in tables. The iptables command allows you to alter these tables and rule
sets.
Security in Linux
309
The Linux kernel maintains three tables, each for a particular category of functions of
the packet filter:
filter
This table holds the bulk of the filter rules, because it implements the packet filtering
mechanism in the stricter sense, which determines whether packets are let through
(ACCEPT) or discarded (DROP), for example.
nat
This table defines any changes to the source and target addresses of packets. Using
these functions also allows you to implement masquerading, which is a special case
of NAT used to link a private network with the Internet.
mangle
The rules held in this table make it possible to manipulate values stored in IP
headers (such as the type of service).
310
Figure 23.1
iptables: A Packet's Possible Paths
PREROUTING
incoming packet
mangle
nat
INPUT
mangle
Routing
filter
FORWARD
Processes
mangle
in the local
system
filter
OUTPUT
Routing
mangle
nat
filter
POSTROUTING
mangle
nat
outgoing packet
These tables contain several predefined chains to match packets:
Security in Linux
311
PREROUTING
This chain is applied to incoming packets.
INPUT
This chain is applied to packets destined for the system's internal processes.
FORWARD
This chain is applied to packets that are only routed through the system.
OUTPUT
This chain is applied to packets originating from the system itself.
POSTROUTING
This chain is applied to all outgoing packets.
Figure 23.1, “iptables: A Packet's Possible Paths” (page 311) illustrates the paths along
which a network packet may travel on a given system. For the sake of simplicity, the
figure lists tables as parts of chains, but in reality these chains are held within the tables
themselves.
In the simplest of all possible cases, an incoming packet destined for the system itself
arrives at the eth0 interface. The packet is first referred to the PREROUTING chain
of the mangle table then to the PREROUTING chain of the nat table. The following
step, concerning the routing of the packet, determines that the actual target of the
packet is a process of the system itself. After passing the INPUT chains of the mangle
and the filter table, the packet finally reaches its target, provided that the rules of
the filter table are actually matched.
23.1.2 Masquerading Basics
Masquerading is the Linux-specific form of NAT (network address translation). It can
be used to connect a small LAN (where hosts use IP addresses from the private
range—see Section 38.1.2, “Netmasks and Routing” (page 551)) with the Internet (where
official IP addresses are used). For the LAN hosts to be able to connect to the Internet,
their private addresses are translated to an official one. This is done on the router, which
acts as the gateway between the LAN and the Internet. The underlying principle is a
simple one: The router has more than one network interface, typically a network card
and a separate interface connecting with the Internet. While the latter links the router
with the outside world, one or several others link it with the LAN hosts. With these
312
hosts in the local network connected to the network card (such as eth0) of the router,
they can send any packets not destined for the local network to their default gateway
or router.
IMPORTANT: Using the Correct Network Mask
When configuring your network, make sure both the broadcast address and
the netmask are the same for all local hosts. Failing to do so prevents packets
from being routed properly.
As mentioned, whenever one of the LAN hosts sends a packet destined for an Internet
address, it goes to the default router. However, the router must be configured before it
can forward such packets. For security reasons, SUSE Linux does not enable this in a
default installation. To enable it, set the variable IP_FORWARD in the file /etc/
sysconfig/sysctl to IP_FORWARD=yes.
The target host of the connection can see your router, but knows nothing about the host
in your internal network where the packets originated. This is why the technique is
called masquerading. Because of the address translation, the router is the first destination
of any reply packets. The router must identify these incoming packets and translate
their target addresses, so packets can be forwarded to the correct host in the local network.
With the routing of inbound traffic depending on the masquerading table, there is no
way to open a connection to an internal host from the outside. For such a connection,
there would be no entry in the table. In addition, any connection already established
has a status entry assigned to it in the table, so the entry cannot be used by another
connection.
As a consequence of all this, you might experience some problems with a number of
application protocols, such as ICQ, cucme, IRC (DCC, CTCP), and FTP (in PORT
mode). Netscape, the standard FTP program, and many others use the PASV mode.
This passive mode is much less problematic as far as packet filtering and masquerading
are concerned.
23.1.3 Firewalling Basics
Firewall is probably the term most widely used to describe a mechanism that provides
and manages a link between networks while also controlling the data flow between
Security in Linux
313
them. Strictly speaking, the mechanism described in this section is called a packet filter.
A packet filter regulates the data flow according to certain criteria, such as protocols,
ports, and IP addresses. This allows you to block packets that, according to their addresses, are not supposed to reach your network. To allow public access to your Web
server, for example, explicitly open the corresponding port. However, a packet filter
does not scan the contents of packets with legitimate addresses, such as those directed
to your Web server. For example, if incoming packets were intended to compromise a
CGI program on your Web server, the packet filter would still let them through.
A more effective but more complex mechanism is the combination of several types of
systems, such as a packet filter interacting with an application gateway or proxy. In
this case, the packet filter rejects any packets destined for disabled ports. Only packets
directed to the application gateway are accepted. This gateway or proxy pretends to be
the actual client of the server. In a sense, such a proxy could be considered a masquerading host on the protocol level used by the application. One example for such a proxy
is Squid, an HTTP proxy server. To use Squid, the browser must be configured to
communicate via the proxy. Any HTTP pages requested are served from the proxy
cache and pages not found in the cache are fetched from the Internet by the proxy. As
another example, the SUSE proxy-suite (proxy-suite) provides a proxy for the
FTP protocol.
The following section focuses on the packet filter that comes with SUSE Linux. For
further information about packet filtering and firewalling, read the Firewall HOWTO
included in the howto package. If this package is installed, read the HOWTO with
less /usr/share/doc/howto/en/txt/Firewall-HOWTO.gz.
23.1.4 SuSEfirewall2
SuSEfirewall2 is a script that reads the variables set in /etc/sysconfig/
SuSEfirewall2 to generate a set of iptables rules. It defines three security zones,
although only the first and the second one are considered in the following sample configuration:
External Zone
Given that there is no way to control what is happening on the external network,
the host needs to be protected from it. In most cases, the external network is the
Internet, but it could be another insecure network, such as a WLAN.
314
Internal Zone
This refers to the private network, in most cases the LAN. If the hosts on this network
use IP addresses from the private range (see Section 38.1.2, “Netmasks and Routing”
(page 551)), enable network address translation (NAT), so hosts on the internal network can access the external one.
Demilitarized Zone (DMZ)
While hosts located in this zone can be reached both from the external and the internal network, they cannot access the internal network themselves. This setup can be
used to put an additional line of defense in front of the internal network, because
the DMZ systems are isolated from the internal network.
Any kind of network traffic not explicitly allowed by the filtering rule set is suppressed
by iptables. Therefore, each of the interfaces with incoming traffic must be placed into
one of the three zones. For each of the zones, define the services or protocols allowed.
The rule set is only applied to packets originating from remote hosts. Locally generated
packets are not captured by the firewall.
The configuration can be performed with YaST (see Section “Configuring with YaST”
(page 315)). It can also be made manually in the file /etc/sysconfig/
SuSEfirewall2, which is well commented. Additionally, a number of example
scenarios are available in /usr/share/doc/packages/SuSEfirewall2/
EXAMPLES.
Configuring with YaST
IMPORTANT: Automatic Firewall Configuration
After the installation, YaST automatically starts a firewall on all configured interfaces. If a server is configured and activated on the system, YaST can modify
the automatically-generated firewall configuration with the options Open Ports
on Selected Interface in Firewall or Open Ports on Firewall in the server configuration modules. Some server module dialogs include a Firewall Details button
for activating additional services and ports. The YaST firewall configuration
module can be used to activate, deactivate, or reconfigure the firewall.
The YaST dialogs for the graphical configuration can be accessed from the YaST
Control Center. Select Security and Users → Firewall. The configuration is divided
into seven sections that can be accessed directly from the tree structure on the left side.
Security in Linux
315
Start-Up
Set the start-up behavior in this dialog. In a default installation, SuSEfirewall2 is
started automatically. You can also start and stop the firewall here. To implement
your new settings in a running firewall, use Save Settings and Restart Firewall Now.
Figure 23.2
The YaST Firewall Configuration
Interfaces
All known network interfaces are listed here. To remove an interface from a zone,
select the interface, press Change, and choose No Zone Assigned. To add an interface
to a zone, select the interface, press Change and choose any of the available zones.
You may also create a special interface with your own settings by using Custom.
Allowed Services
You need this option to offer services from your system to a zone from which it is
protected. By default, the system is only protected from external zones. Explicitly
allow the services that should be available to external hosts. Activate the services
after selecting the desired zone in Allowed Services for Selected Zone.
Masquerading
Masquerading hides your internal network from external networks, such as the Internet, while enabling hosts in the internal network to access the external network
transparently. Requests from the external network to the internal one are blocked
and requests from the internal network seem to be issued by the masquerading
316
server when seen externally. If special services of an internal machine need to be
available to the external network, add special redirect rules for the service.
Broadcast
In this dialog, configure the UDP ports that allow broadcasts. Add the required port
numbers or services to the appropriate zone, separated by spaces. See also the file
/etc/services.
The logging of broadcasts that are not accepted can be enabled here. This may be
problematic, because Windows hosts use broadcasts to know about each other and
so generate many packets that are not accepted.
IPsec Support
Configure whether the IPsec service should be available to the external network in
this dialog. Configure which packets are trusted under Details.
Logging Level
There are two rules for the logging: accepted and not accepted packets. Packets that
are not accepted are DROPPED or REJECTED. Select from Log All, Log Critical,
or Do Not Log Any for both of them.
When completed with the firewall configuration, exit this dialog with Next. A zoneoriented summary of your firewall configuration then opens. In it, check all settings.
All services, ports, and protocols that have been allowed are listed in this summary. To
modify the configuration, use Back. Press Accept to save your configuration.
Configuring Manually
The following paragraphs provide step-by-step instructions for a successful configuration. Each configuration item is marked as to whether it is relevant to firewalling or
masquerading. Aspects related to the DMZ (demilitarized zone) as mentioned in the
configuration file are not covered here. They are applicable only to a more complex
network infrastructure found in larger organizations (corporate networks), which require
extensive configuration and in-depth knowledge about the subject.
First, use the YaST module System Services (Runlevel) to enable SuSEfirewall2 in
your runlevel (3 or 5 most likely). It sets the symlinks for the SuSEfirewall2_* scripts
in the /etc/init.d/rc?.d/ directories.
Security in Linux
317
FW_DEV_EXT (firewall, masquerading)
The device linked to the Internet. For a modem connection, enter ppp0. For an ISDN
link, use ippp0. DSL connections use dsl0. Specify auto to use the interface
that corresponds to the default route.
FW_DEV_INT (firewall, masquerading)
The device linked to the internal, private network (such as eth0). Leave this blank
if there is no internal network and the firewall protects only the host on which it
runs.
FW_ROUTE (firewall, masquerading)
If you need the masquerading function, set this to yes. Your internal hosts will not
be visible to the outside, because their private network addresses (e.g.,
192.168.x.x) are ignored by Internet routers.
For a firewall without masquerading, only set this to yes if you want to allow access
to the internal network. Your internal hosts need to use officially registered IPs in
this case. Normally, however, you should not allow access to your internal network
from the outside.
FW_MASQUERADE (masquerading)
Set this to yes if you need the masquerading function. This provides a virtually
direct connection to the Internet for the internal hosts. It is more secure to have a
proxy server between the hosts of the internal network and the Internet. Masquerading
is not needed for services a proxy server provides.
FW_MASQ_NETS (masquerading)
Specify the hosts or networks to masquerade, leaving a space between the individual
entries. For example:
FW_MASQ_NETS="192.168.0.0/24 192.168.10.1"
FW_PROTECT_FROM_INT (firewall)
Set this to yes to protect your firewall host from attacks originating in your internal
network. Services are only available to the internal network if explicitly enabled.
Also see FW_SERVICES_INT_TCP and FW_SERVICES_INT_UDP.
FW_SERVICES_EXT_TCP (firewall)
Enter the TCP ports that should be made available. Leave this blank for a normal
workstation at home that should not offer any services.
318
FW_SERVICES_EXT_UDP (firewall)
Leave this blank unless you run a UDP service and want to make it available to the
outside. The services that use UDP include include DNS servers, IPSec, TFTP,
DHCP and others. In that case, enter the UDP ports to use.
FW_SERVICES_INT_TCP (firewall)
With this variable, define the services available for the internal network. The notation
is the same as for FW_SERVICES_EXT_TCP, but the settings are applied to the
internal network. The variable only needs to be set if FW_PROTECT_FROM_INT
is set to yes.
FW_SERVICES_INT_UDP (firewall)
See FW_SERVICES_INT_TCP.
After configuring the firewall, test your setup. The firewall rule sets are created by entering SuSEfirewall2 start as root. Then use telnet, for example, from an
external host to see whether the connection is actually denied. After that, review /var/
log/messages, where you should see something like this:
Mar 15 13:21:38 linux kernel: SFW2-INext-DROP-DEFLT IN=eth0
OUT= MAC=00:80:c8:94:c3:e7:00:a0:c9:4d:27:56:08:00 SRC=192.168.10.0
DST=192.168.10.1 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=15330 DF PROTO=TCP
SPT=48091 DPT=23 WINDOW=5840 RES=0x00 SYN URGP=0
OPT (020405B40402080A061AFEBC0000000001030300)
Other packages to test your firewall setup are nmap or nessus. The documentation of
nmap is found at /usr/share/doc/packages/nmap and the documentation of
nessus resides in the directory /usr/share/doc/packages/nessus-core after
installing the respective package.
23.1.5 For More Information
The most up-to-date information and other documentation about the SuSEfirewall2
package is found in /usr/share/doc/packages/SuSEfirewall2. The home
page of the netfilter and iptables project, http://www.netfilter.org, provides
a large collection of documents in many languages.
Security in Linux
319
23.2
SSH: Secure Network
Operations
With more and more computers installed in networked environments, it often becomes
necessary to access hosts from a remote location. This normally means that a user sends
login and password strings for authentication purposes. As long as these strings are
transmitted as plain text, they could be intercepted and misused to gain access to that
user account without the authorized user even knowing about it. Apart from the fact
that this would open all the user's files to an attacker, the illegal account could be used
to obtain administrator or root access or to penetrate other systems. In the past, remote
connections were established with telnet, which offers no guards against eavesdropping
in the form of encryption or other security mechanisms. There are other unprotected
communication channels, like the traditional FTP protocol and some remote copying
programs.
The SSH suite provides the necessary protection by encrypting the authentication strings
(usually a login name and a password) and all the other data exchanged between the
hosts. With SSH, the data flow could still be recorded by a third party, but the contents
are encrypted and cannot be reverted to plain text unless the encryption key is known.
So SSH enables secure communication over insecure networks, such as the Internet.
The SSH flavor that comes with SUSE Linux is OpenSSH.
23.2.1 The OpenSSH Package
SUSE Linux installs the package OpenSSH by default. The programs ssh, scp, and sftp
are then available as alternatives to telnet, rlogin, rsh, rcp, and ftp. In the default configuration, system access of a SUSE Linux system is only possible with the OpenSSH
utilities and only if the firewall permits access.
23.2.2 The ssh Program
Using the ssh program, it is possible to log in to remote systems and work interactively.
It replaces both telnet and rlogin. The slogin program is just a symbolic link pointing
to ssh. For example, log in to the host sun with the command ssh sun. The host then
prompts for the password on sun.
320
After successful authentication, you can work on the remote command line or use interactive applications, such as YaST. If the local username is different from the remote
username, you can log in using a different login name with ssh -l augustine
sun or ssh [email protected]
Furthermore, ssh offers the possibility to run commands on remote systems, as known
from rsh. In the following example, run the command uptime on the host sun and
create a directory with the name tmp. The program output is displayed on the local
terminal of the host earth.
ssh otherplanet "uptime; mkdir tmp"
[email protected]'s password:
1:21pm up 2:17, 9 users, load average: 0.15, 0.04, 0.02
Quotation marks are necessary here to send both instructions with one command. It is
only by doing this that the second command is executed on sun.
23.2.3 scp—Secure Copy
scp copies files to a remote machine. It is a secure and encrypted substitute for rcp. For
example, scp MyLetter.tex sun: copies the file MyLetter.tex from the host
earth to the host sun. If the username on earth is different than the username on sun,
specify the latter using the [email protected] format. There is no -l option for this
command.
After the correct password is entered, scp starts the data transfer and shows a growing
row of asterisks to simulate a progress bar. In addition, the program displays the estimated time of arrival to the right of the progress bar. Suppress all output by giving the
option -q.
scp also provides a recursive copying feature for entire directories. The command
scp -r src/ sun:backup/ copies the entire contents of the directory src including all subdirectories to the backup directory on the host sun. If this subdirectory does
not exist yet, it is created automatically.
The option -p tells scp to leave the time stamp of files unchanged. -C compresses the
data transfer. This minimizes the data volume to transfer, but creates a heavier burden
on the processor.
Security in Linux
321
23.2.4 sftp—Secure File Transfer
The sftp program can be used instead of scp for secure file transfer. During an sftp
session, you can use many of the commands known from ftp. The sftp program may
be a better choice than scp, especially when transferring data for which the filenames
are unknown.
23.2.5 The SSH Daemon (sshd)—Server-Side
To work with the SSH client programs ssh and scp, a server, the SSH daemon, must
be running in the background, listening for connections on TCP/IP port 22. The
daemon generates three key pairs when starting for the first time. Each key pair consist
of a private and a public key. Therefore, this procedure is referred to as public key–based.
To guarantee the security of the communication via SSH, access to the private key files
must be restricted to the system administrator. The file permissions are set accordingly
by the default installation. The private keys are only required locally by the SSH daemon
and must not be given to anyone else. The public key components (recognizable by the
name extension .pub) are sent to the client requesting the connection. They are readable
for all users.
A connection is initiated by the SSH client. The waiting SSH daemon and the requesting
SSH client exchange identification data to compare the protocol and software versions
and to prevent connections through the wrong port. Because a child process of the
original SSH daemon replies to the request, several SSH connections can be made simultaneously.
For the communication between SSH server and SSH client, OpenSSH supports versions 1 and 2 of the SSH protocol. A newly installed SUSE Linux system defaults to
version 2. To continue using version 1 after an update, follow the instructions in /usr/
share/doc/packages/openssh/README.SuSE. This document also describes
how an SSH 1 environment can be transformed into a working SSH 2 environment
with just a few steps.
When using version 1 of SSH, the server sends its public host key and a server key,
which is regenerated by the SSH daemon every hour. Both allow the SSH client to encrypt a freely chosen session key, which is sent to the SSH server. The SSH client also
tells the server which encryption method (cipher) to use.
322
Version 2 of the SSH protocol does not require a server key. Both sides use an algorithm
according to Diffie-Helman to exchange their keys.
The private host and server keys are absolutely required to decrypt the session key and
cannot be derived from the public parts. Only the SSH daemon contacted can decrypt
the session key using its private keys (see man
/usr/share/doc/packages/openssh/RFC.nroff). This initial connection
phase can be watched closely by turning on the verbose debugging option -v of the
SSH client.
Version 2 of the SSH protocol is used by default. Override this to use version 1 of the
protocol with the -1 switch. The client stores all public host keys in ~/.ssh/known
_hosts after its first contact with a remote host. This prevents any man-in-the-middle
attacks—attempts by foreign SSH servers to use spoofed names and IP addresses. Such
attacks are detected either by a host key that is not included in ~/.ssh/known_hosts
or by the server's inability to decrypt the session key in the absence of an appropriate
private counterpart.
It is recommended to back up the private and public keys stored in /etc/ssh/ in a
secure, external location. In this way, key modifications can be detected and the old
ones can be used again after a reinstallation. This spares users any unsettling warnings.
If it is verified that, despite the warning, it is indeed the correct SSH server, the existing
entry for the system must be removed from ~/.ssh/known_hosts.
23.2.6 SSH Authentication Mechanisms
Now the actual authentication takes place, which, in its simplest form, consists of entering a password as mentioned above. The goal of SSH was to introduce a secure software
that is also easy to use. Because it is meant to replace rsh and rlogin, SSH must also be
able to provide an authentication method appropriate for daily use. SSH accomplishes
this by way of another key pair, which is generated by the user. The SSH package
provides a helper program for this: ssh-keygen. After entering ssh-keygen -t rsa
or ssh-keygen -t dsa, the key pair is generated and you are prompted for the base
filename in which to store the keys.
Confirm the default setting and answer the request for a passphrase. Even if the software
suggests an empty passphrase, a text from 10 to 30 characters is recommended for the
procedure described here. Do not use short and simple words or phrases. Confirm by
Security in Linux
323
repeating the passphrase. Subsequently, you will see where the private and public keys
are stored, in this example, the files id_rsa and id_rsa.pub.
Use ssh-keygen -p -t rsa or ssh-keygen -p -t dsa to change your old
passphrase. Copy the public key component (id_rsa.pub in the example) to the remote machine and save it to ~/.ssh/authorized_keys. You will be asked to
authenticate yourself with your passphrase the next time you establish a connection. If
this does not occur, verify the location and contents of these files.
In the long run, this procedure is more troublesome than giving your password each
time. Therefore, the SSH package provides another tool, ssh-agent, which retains the
private keys for the duration of an X session. The entire X session is started as a child
process of ssh-agent. The easiest way to do this is to set the variable usessh at the
beginning of the .xsession file to yes and log in via a display manager, such as
KDM or XDM. Alternatively, enter ssh-agent startx.
Now you can use ssh or scp as usual. If you have distributed your public key as described
above, you are no longer prompted for your password. Take care of terminating your
X session or locking it with a password protection application, such as xlock.
All the relevant changes that resulted from the introduction of version 2 of the SSH
protocol are also documented in the file /usr/share/doc/packages/openssh/
README.SuSE.
23.2.7 X, Authentication, and Forwarding
Mechanisms
Beyond the previously described security-related improvements, SSH also simplifies
the use of remote X applications. If you run ssh with the option -X, the DISPLAY
variable is automatically set on the remote machine and all X output is exported to the
remote machine over the existing SSH connection. At the same time, X applications
started remotely and locally viewed with this method cannot be intercepted by unauthorized individuals.
By adding the option -A, the ssh-agent authentication mechanism is carried over to the
next machine. This way, you can work from different machines without having to enter
a password, but only if you have distributed your public key to the destination hosts
and properly saved it there.
324
Both mechanisms are deactivated in the default settings, but can be permanently activated at any time in the systemwide configuration file /etc/ssh/sshd_config
or the user's ~/.ssh/config.
ssh can also be used to redirect TCP/IP connections. In the examples below, SSH is
told to redirect the SMTP and the POP3 port, respectively:
ssh -L 25:sun:25 earth
With this command, any connection directed to earth port 25 (SMTP) is redirected to
the SMTP port on sun via an encrypted channel. This is especially useful for those using
SMTP servers without SMTP-AUTH or POP-before-SMTP features. From any arbitrary
location connected to a network, e-mail can be transferred to the “home” mail server
for delivery. Similarly, all POP3 requests (port 110) on earth can be forwarded to the
POP3 port of sun with this command:
ssh -L 110:sun:110 earth
Both commands must be executed as root, because the connection is made to privileged
local ports. E-mail is sent and retrieved by normal users in an existing SSH connection.
The SMTP and POP3 host must be set to localhost for this to work. Additional information can be found in the manual pages for each of the programs described above
and also in the files under /usr/share/doc/packages/openssh.
23.3
Encrypting Partitions and Files
Every user has some confidential data that third parties should not be able to access.
The more connected and mobile you are, the more carefully you should handle your
data. The encryption of files or entire partitions is recommended if others have access
over a network connection or direct physical access.
WARNING: Encrypted Media Is Limited Protection
Be aware that with the methods described in this section, you cannot protect
your running system from being compromised. After the encrypted media is
successfully mounted, everybody with appropriate permissions have access to
it. Encrypted media makes sense if you lose your computer or it is stolen and
unauthorized individuals want to read your confidental data.
The following list features a number of imaginable usage scenarios.
Security in Linux
325
Laptops
If you travel with your laptop, it is a good idea to encrypt hard disk partitions containing confidential data. If you lose your laptop or if it is stolen, your data will be
out of reach if it resides in an encrypted file system or a single encrypted file.
Removable Media
USB flash drives or external hard disks are as prone to being stolen as laptops. An
encrypted file system provides protection against third-party access.
Workstations
In companies where almost everyone has access to your computer, it can makes
sense to encrypt partition or single files.
23.3.1 Setting Up a Crypto File System with
YaST
YaST offers the encryption of files or partitions during installation as well as in an already installed system. An encrypted file can be created at any time, because it fits
nicely in an existing partition layout. To encrypt an entire partition, dedicate a partition
for encryption in the partition layout. The standard partitioning proposal as suggested
by YaST does not, by default, include an encrypted partition. Add it manually in the
partitioning dialog.
Creating an Encrypted Partition during Installation
WARNING: Password Input
Observe the warnings about password security when setting the password for
encrypted partitions and memorize it well. Without the password, the encrypted
data cannot be accessed or restored.
The YaST expert dialog for partitioning, described in Section “Partitioner” (Chapter 3,
System Configuration with YaST, ↑Start-Up), offers the options needed for creating an
encrypted partition. Click Create like when creating a regular partition. In the dialog
that opens, enter the partitioning parameters for the new partition, such as the desired
formatting and the mount point. Complete the process by clicking Encrypt File System.
In the following dialog, enter the password twice. The new encrypted partition is created
326
after the partitioning dialog is closed by clicking OK. While booting, the operating
system requests the password before mounting the partition.
If you do not want to mount the encrypted partition during start-up, click Enter when
prompted for the password. Then decline the offer to enter the password again. In this
case, the encrypted file system is not mounted and the operating system continues
booting, blocking access to your data. The partition is available to all users once it has
been mounted.
If the encrypted file system should only be mounted when necessary, enable Do Not
Mount During Booting in the fstab Options dialog. The respective partition will not be
mounted when the system is booted. To make it available afterwards, mount it manually
with mount name_of_partition mount_point. Enter the password when
prompted to do so. After finishing your work with the partition, unmount it with
umount name_of_partition to protect it from access by other users.
Creating an Encrypted Partition on a Running System
WARNING: Activating Encryption in a Running System
It is also possible to create encrypted partitions on a running system like during
installation. However, encrypting an existing partition destroys all data on it.
On a running system, select System → Partitioning in the YaST control center. Click
Yes to proceed. Instead of selecting Create as mentioned above, click Edit. The rest of
the procedure is the same.
Installing Encrypted Files
Instead of using a partition, it is possible to create encrypted file systems within single
files for holding confidential data. These are created from the same YaST dialog. Select
Crypt File and enter the path to the file to create along with its intended size. Accept
the proposed formatting settings and the file system type. Then specify the mount point
and decide whether the encrypted file system should be mounted when the system is
booted.
The advantage of encrypted files is that they can be added without repartitioning the
hard disk. They are mounted with the help of a loop device and behave just like normal
partitions.
Security in Linux
327
Using vi to Encrypt Files
The disadvantage of using encrypted partitions is that while the partition is mounted,
at least root can access the data. To prevent this, vi can be used in encrypted mode.
Use vi -x filename to edit a new file. vi prompts you to set a password, after
which it encrypts the content of the file. Whenever you access this file, vi requests the
correct password.
For even more security, you can place the encrypted text file in an encrypted partition.
This is recommended because the encryption used in vi is not very strong.
23.3.2 Encrypting the Content of
Removable Media
YaST treats removable media like external hard disks or USB flash drives like any
other hard disk. Files or partitions on such media can be encrypted as described above.
However, do not select to mount these media when the system is booted, because they
are usually only connected while the system is running.
23.4
Security and Confidentiality
One of the main characteristics of a Linux or UNIX system is its ability to handle several users at the same time (multiuser) and to allow these users to perform several tasks
(multitasking) on the same computer simultaneously. Moreover, the operating system
is network transparent. The users often do not know whether the data and applications
they are using are provided locally from their machine or made available over the network.
With the multiuser capability, the data of different users must be stored separately. Security and privacy need to be guaranteed. Data security was already an important issue,
even before computers could be linked through networks. Just like today, the most important concern was the ability to keep data available in spite of a lost or otherwise
damaged data medium, a hard disk in most cases.
This section is primarily focused on confidentiality issues and on ways to protect the
privacy of users, but it cannot be stressed enough that a comprehensive security concept
328
should always include procedures to have a regularly updated, workable, and tested
backup in place. Without this, you could have a very hard time getting your data
back—not only in the case of some hardware defect, but also if the suspicion arises that
someone has gained unauthorized access and tampered with files.
23.4.1 Local Security and Network Security
There are several ways of accessing data:
• personal communication with people who have the desired information or access
to the data on a computer
• directly from the console of a computer (physical access)
• over a serial line
• using a network link
In all these cases, a user should be authenticated before accessing the resources or data
in question. A Web server might be less restrictive in this respect, but you still would
not want it to disclose all your personal data to any surfer.
In the list above, the first case is the one where the highest amount of human interaction
is involved, such as when you are contacting a bank employee and are required to prove
that you are the person owning that bank account. Then you are asked to provide a
signature, a PIN, or a password to prove that you are the person you claim to be. In
some cases, it might be possible to elicit some intelligence from an informed person
just by mentioning known bits and pieces to win the confidence of that person by using
clever rhetoric. The victim could be led to reveal gradually more information, maybe
without even becoming aware of it. Among hackers, this is called social engineering.
You can only guard against this by educating people and by dealing with language and
information in a conscious way. Before breaking into computer systems, attackers often
try to target receptionists, service people working with the company, or even family
members. In many cases, such an attack based on social engineering is only discovered
at a much later time.
A person wanting to obtain unauthorized access to your data could also use the traditional way and try to get at your hardware directly. Therefore, the machine should be
protected against any tampering so that no one can remove, replace, or cripple its
components. This also applies to backups and even any network cable or the power
Security in Linux
329
cord. Also secure the boot procedure, because there are some well-known key combinations that might provoke unusual behavior. Protect yourself against this by setting
passwords for the BIOS and the boot loader.
Serial terminals connected to serial ports are still used in many places. Unlike network
interfaces, they do not rely on a network protocol to communicate with the host. A
simple cable or an infrared port is used to send plain characters back and forth between
the devices. The cable itself is the weakest point of such a system: with an older printer
connected to it, it is easy to record anything that runs over the wires. What can be
achieved with a printer can also be accomplished in other ways, depending on the effort
that goes into the attack.
Reading a file locally on a host requires other access rules than opening a network
connection with a server on a different host. There is a distinction between local security and network security. The line is drawn where data must be put into packets to be
sent somewhere else.
Local Security
Local security starts with the physical environment in the location where the computer
is running. Set up your machine in a place where security is in line with your expectations
and needs. The main goal of local security is to keep users separate from each other,
so no user can assume the permissions or the identity of another. This is a general rule
to be observed, but it is especially true for the user root, who holds the supreme
power on the system. root can take on the identity of any other local user without
being prompted for the password and read any locally stored file.
Passwords
On a Linux system, passwords are not stored as plain text and the text string entered is
not simply matched with the saved pattern. If this were the case, all accounts on your
system would be compromised as soon as someone got access to the corresponding
file. Instead, the stored password is encrypted and, each time it is entered, is encrypted
again and the two encrypted strings are compared. This only provides more security if
the encrypted password cannot be reverse-computed into the original text string.
This is actually achieved by a special kind of algorithm, also called trapdoor algorithm,
because it only works in one direction. An attacker who has obtained the encrypted
string is not able to get your password by simply applying the same algorithm again.
330
Instead, it would be necessary to test all the possible character combinations until a
combination is found that looks like your password when encrypted. With passwords
eight characters long, there are quite a number of possible combinations to calculate.
In the seventies, it was argued that this method would be more secure than others due
to the relative slowness of the algorithm used, which took a few seconds to encrypt just
one password. In the meantime, however, PCs have become powerful enough to do
several hundred thousand or even millions of encryptions per second. Because of this,
encrypted passwords should not be visible to regular users (/etc/shadow cannot be
read by normal users). It is even more important that passwords are not easy to guess,
in case the password file becomes visible due to some error. Consequently, it is not really useful to “translate” a password like “tantalize” into “[email protected]@1lz3”.
Replacing some letters of a word with similar looking numbers is not safe enough.
Password cracking programs that use dictionaries to guess words also play with substitutions like that. A better way is to make up a word with no common meaning, something
that only makes sense to you personally, like the first letters of the words of a sentence
or the title of a book, such as “The Name of the Rose” by Umberto Eco. This would
give the following safe password: “TNotRbUE9”. In contrast, passwords like “beerbuddy” or “jasmine76” are easily guessed even by someone who has only some casual
knowledge about you.
The Boot Procedure
Configure your system so it cannot be booted from a floppy or from CD, either by removing the drives entirely or by setting a BIOS password and configuring the BIOS to
allow booting from a hard disk only. Normally, a Linux system is started by a boot
loader, allowing you to pass additional options to the booted kernel. Prevent others
from using such parameters during boot by setting an additional password in /boot/
grub/menu.lst (see Chapter 29, The Boot Loader (page 427)). This is crucial to
your system's security. Not only does the kernel itself run with root permissions, but
it is also the first authority to grant root permissions at system start-up.
File Permissions
As a general rule, always work with the most restrictive privileges possible for a given
task. For example, it is definitely not necessary to be root to read or write e-mail. If
the mail program has a bug, this bug could be exploited for an attack that acts with ex-
Security in Linux
331
actly the permissions of the program when it was started. By following the above rule,
minimize the possible damage.
The permissions of the more than 200,000 files included in a SUSE distribution are
carefully chosen. A system administrator who installs additional software or other files
should take great care when doing so, especially when setting the permission bits. Experienced and security-conscious system administrators always use the -l option with
the command ls to get an extensive file list, which allows them to detect any incorrect
file permissions immediately. An incorrect file attribute does not only mean that files
could be changed or deleted. These modified files could be executed by root or, in
the case of configuration files, programs could use such files with the permissions of
root. This significantly increases the possibilities of an attacker. Attacks like this are
called cuckoo eggs, because the program (the egg) is executed (hatched) by a different
user (bird), just like a cuckoo tricks other birds into hatching its eggs.
A SUSE Linux system includes the files permissions, permissions.easy,
permissions.secure, and permissions.paranoid, all in the directory
/etc. The purpose of these files is to define special permissions, such as world-writable
directories or, for files, the setuser ID bit (programs with the setuser ID bit set do not
run with the permissions of the user that has launched it, but with the permissions of
the file owner, in most cases root). An administrator can use the file /etc/
permissions.local to add his own settings.
To define which of the above files is used by SUSE's configuration programs to set
permissions accordingly, select Security in YaST. To learn more about the topic, read
the comments in /etc/permissions or consult the manual page of chmod
(man chmod).
Buffer Overflows and Format String Bugs
Special care must be taken whenever a program is supposed to process data that can or
could be changed by a user, but this is more of an issue for the programmer of an application than for regular users. The programmer must make sure that his application interprets data in the correct way, without writing it into memory areas that are too small
to hold it. Also, the program should hand over data in a consistent manner, using the
interfaces defined for that purpose.
A buffer overflow can happen if the actual size of a memory buffer is not taken into
account when writing to that buffer. There are cases where this data (as generated by
332
the user) uses up some more space than what is available in the buffer. As a result, data
is written beyond the end of that buffer area, which, under certain circumstances, makes
it possible for a program to execute program sequences influenced by the user (and not
by the programmer), rather than just processing user data. A bug of this kind may have
serious consequences, especially if the program is being executed with special privileges
(see Section “File Permissions” (page 331)).
Format string bugs work in a slightly different way, but again it is the user input that
could lead the program astray. In most cases, these programming errors are exploited
with programs executed with special permissions—setuid and setgid programs—which
also means that you can protect your data and your system from such bugs by removing
the corresponding execution privileges from programs. Again, the best way is to apply
a policy of using the lowest possible privileges (see Section “File Permissions”
(page 331)).
Given that buffer overflows and format string bugs are bugs related to the handling of
user data, they are not only exploitable if access has been given to a local account.
Many of the bugs that have been reported can also be exploited over a network link.
Accordingly, buffer overflows and format string bugs should be classified as being
relevant for both local and network security.
Viruses
Contrary to what some people say, there are viruses that run on Linux. However, the
viruses that are known were released by their authors as a proof of concept to prove
that the technique works as intended. None of these viruses have been spotted in the
wild so far.
Viruses cannot survive and spread without a host on which to live. In this case, the host
would be a program or an important storage area of the system, such as the master boot
record, which needs to be writable for the program code of the virus. Owing to its
multiuser capability, Linux can restrict write access to certain files, especially important
with system files. Therefore, if you did your normal work with root permissions, you
would increase the chance of the system being infected by a virus. In contrast, if you
follow the principle of using the lowest possible privileges as mentioned above, chances
of getting a virus are slim.
Apart from that, you should never rush into executing a program from some Internet
site that you do not really know. SUSE's RPM packages carry a cryptographic signature
as a digital label that the necessary care was taken to build them. Viruses are a typical
Security in Linux
333
sign that the administrator or the user lacks the required security awareness, putting at
risk even a system that should be highly secure by its very design.
Viruses should not be confused with worms, which belong to the world of networks
entirely. Worms do not need a host to spread.
Network Security
Network security is important for protecting from an attack that is started outside. The
typical login procedure requiring a username and a password for user authentication is
still a local security issue. In the particular case of logging in over a network, differentiate between the two security aspects. What happens until the actual authentication is
network security and anything that happens afterwards is local security.
X Window System and X Authentication
As mentioned at the beginning, network transparency is one of the central characteristics
of a UNIX system. X, the windowing system of UNIX operating systems, can make
use of this feature in an impressive way. With X, it is basically no problem to log in at
a remote host and start a graphical program that is then sent over the network to be
displayed on your computer.
When an X client should be displayed remotely using an X server, the latter should
protect the resource managed by it (the display) from unauthorized access. In more
concrete terms, certain permissions must be given to the client program. With the X
Window System, there are two ways to do this, called host-based access control and
cookie-based access control. The former relies on the IP address of the host where the
client should run. The program to control this is xhost. xhost enters the IP address of a
legitimate client into a tiny database belonging to the X server. However, relying on
IP addresses for authentication is not very secure. For example, if there were a second
user working on the host sending the client program, that user would have access to
the X server as well—just like someone stealing the IP address. Because of these
shortcomings, this authentication method is not described in more detail here, but you
can learn about it with man xhost.
In the case of cookie-based access control, a character string is generated that is only
known to the X server and to the legitimate user, just like an ID card of some kind. This
cookie (the word goes back not to ordinary cookies, but to Chinese fortune cookies,
which contain an epigram) is stored on login in the file .Xauthority in the user's
334
home directory and is available to any X client wanting to use the X server to display
a window. The file .Xauthority can be examined by the user with the tool xauth.
If you were to rename .Xauthority or if you deleted the file from your home directory by accident, you would not be able to open any new windows or X clients. Read
more about X Window System security mechanisms in the man page of Xsecurity
(man Xsecurity).
SSH (secure shell) can be used to encrypt a network connection completely and forward
it to an X server transparently without the encryption mechanism being perceived by
the user. This is also called X forwarding. X forwarding is achieved by simulating an
X server on the server side and setting a DISPLAY variable for the shell on the remote
host. Further details about SSH can be found in Section 23.2, “SSH: Secure Network
Operations” (page 320).
WARNING
If you do not consider the host where you log in to be a secure host, do not
use X forwarding. With X forwarding enabled, an attacker could authenticate
via your SSH connection to intrude on your X server and sniff your keyboard
input, for instance.
Buffer Overflows and Format String Bugs
As discussed in Section “Buffer Overflows and Format String Bugs” (page 332), buffer
overflows and format string bugs should be classified as issues concerning both local
and network security. As with the local variants of such bugs, buffer overflows in network programs, when successfully exploited, are mostly used to obtain root permissions. Even if that is not the case, an attacker could use the bug to gain access to an
unprivileged local account to exploit any other vulnerabilities that might exist on the
system.
Buffer overflows and format string bugs exploitable over a network link are certainly
the most frequent form of remote attacks in general. Exploits for these—programs to
exploit these newly-found security holes—are often posted on the security mailing lists.
They can be used to target the vulnerability without knowing the details of the code.
Over the years, experience has shown that the availability of exploit codes has contributed to more secure operating systems, obviously due to the fact that operating system
makers were forced to fix the problems in their software. With free software, anyone
has access to the source code (SUSE Linux comes with all available source codes) and
Security in Linux
335
anyone who finds a vulnerability and its exploit code can submit a patch to fix the
corresponding bug.
Denial of Service
The purpose of a denial of service (DoS) attack is to block a server program or even
an entire system, something that could be achieved by various means: overloading the
server, keeping it busy with garbage packets, or exploiting a remote buffer overflow.
Often a DoS attack is made with the sole purpose of making the service disappear.
However, once a given service has become unavailable, communications could become
vulnerable to man-in-the-middle attacks (sniffing, TCP connection hijacking, spoofing)
and DNS poisoning.
Man in the Middle: Sniffing, Hijacking, Spoofing
In general, any remote attack performed by an attacker who puts himself between the
communicating hosts is called a man-in-the-middle attack. What almost all types of
man-in-the-middle attacks have in common is that the victim is usually not aware that
there is something happening. There are many possible variants, for example, the attacker
could pick up a connection request and forward that to the target machine. Now the
victim has unwittingly established a connection with the wrong host, because the other
end is posing as the legitimate destination machine.
The simplest form of a man-in-the-middle attack is called sniffer—the attacker is “just”
listening to the network traffic passing by. As a more complex attack, the “man in the
middle” could try to take over an already established connection (hijacking). To do so,
the attacker would need to analyze the packets for some time to be able to predict the
TCP sequence numbers belonging to the connection. When the attacker finally seizes
the role of the target host, the victims notice this, because they get an error message
saying the connection was terminated due to a failure. The fact that there are protocols
not secured against hijacking through encryption, which only perform a simple authentication procedure upon establishing the connection, makes it easier for attackers.
Spoofing is an attack where packets are modified to contain counterfeit source data,
usually the IP address. Most active forms of attack rely on sending out such fake
packets—something that, on a Linux machine, can only be done by the superuser
(root).
336
Many of the attacks mentioned are carried out in combination with a DoS. If an attacker
sees an opportunity to bring down a certain host abruptly, even if only for a short time,
it makes it easier for him to push the active attack, because the host will not be able to
interfere with the attack for some time.
DNS Poisoning
DNS poisoning means that the attacker corrupts the cache of a DNS server by replying
to it with spoofed DNS reply packets, trying to get the server to send certain data to a
victim who is requesting information from that server. Many servers maintain a trust
relationship with other hosts, based on IP addresses or hostnames. The attacker needs
a good understanding of the actual structure of the trust relationships among hosts to
disguise itself as one of the trusted hosts. Usually, the attacker analyzes some packets
received from the server to get the necessary information. The attacker often needs to
target a well-timed DoS attack at the name server as well. Protect yourself by using
encrypted connections that are able to verify the identity of the hosts to which to connect.
Worms
Worms are often confused with viruses, but there is a clear difference between the two.
Unlike viruses, worms do not need to infect a host program to live. Instead, they are
specialized to spread as quickly as possible on network structures. The worms that appeared in the past, such as Ramen, Lion, or Adore, make use of well-known security
holes in server programs like bind8 or lprNG. Protection against worms is relatively
easy. Given that some time elapses between the discovery of a security hole and the
moment the worm hits your server, there is a good chance that an updated version of
the affected program is available on time. That is only useful if the administrator actually installs the security updates on the systems in question.
23.4.2 Some General Security Tips and
Tricks
To handle security competently, it is important to keep up with new developments and
stay informed about the latest security issues. One very good way to protect your systems
against problems of all kinds is to get and install the updated packages recommended
by security announcements as quickly as possible. SUSE security announcements are
published on a mailing list to which you can subscribe by following the link http://
Security in Linux
337
www.novell.com/linux/security/securitysupport.html. The list
[email protected] is a first-hand source of information regarding updated packages and includes members of SUSE's security team among its
active contributors.
The mailing list [email protected] is a good place to discuss any security
issues of interest. Subscribe to it on the same Web page.
[email protected] is one of the best-known security mailing lists
worldwide. Reading this list, which receives between 15 and 20 postings per day, is
recommended. More information can be found at http://www.securityfocus
.com.
The following is a list of rules you may find useful in dealing with basic security concerns:
• According to the rule of using the most restrictive set of permissions possible for
every job, avoid doing your regular jobs as root. This reduces the risk of getting
a cuckoo egg or a virus and protects you from your own mistakes.
• If possible, always try to use encrypted connections to work on a remote machine.
Using ssh (secure shell) to replace telnet, ftp, rsh, and rlogin should be
standard practice.
• Avoid using authentication methods based on IP addresses alone.
• Try to keep the most important network-related packages up-to-date and subscribe
to the corresponding mailing lists to receive announcements on new versions of
such programs (bind, sendmail, ssh, etc.). The same should apply to software relevant to local security.
• Change the /etc/permissions file to optimize the permissions of files crucial
to your system's security. If you remove the setuid bit from a program, it might
well be that it cannot do its job anymore in the intended way. On the other hand,
consider that, in most cases, the program will also have ceased to be a potential
security risk. You might take a similar approach with world-writable directories
and files.
• Disable any network services you do not absolutely require for your server to work
properly. This makes your system safer. Open ports, with the socket state LISTEN,
can be found with the program netstat. As for the options, it is recommended to
338
use netstat -ap or netstat -anp. The -p option allows you to see which
process is occupying a port under which name.
Compare the netstat results with those of a thorough port scan done from outside
your host. An excellent program for this job is nmap, which not only checks out
the ports of your machine, but also draws some conclusions as to which services
are waiting behind them. However, port scanning may be interpreted as an aggressive
act, so do not do this on a host without the explicit approval of the administrator.
Finally, remember that it is important not only to scan TCP ports, but also UDP
ports (options -sS and -sU).
• To monitor the integrity of the files of your system in a reliable way, use the program
AIDE (Advanced Intrusion Detection Environment), available on SUSE Linux.
Encrypt the database created by AIDE to prevent someone from tampering with it.
Furthermore, keep a backup of this database available outside your machine, stored
on an external data medium not connected to it by a network link.
• Take proper care when installing any third-party software. There have been cases
where a hacker had built a trojan horse into the tar archive of a security software
package, which was fortunately discovered very quickly. If you install a binary
package, have no doubts about the site from which you downloaded it.
SUSE's RPM packages are gpg-signed. The key used by SUSE for signing is:
ID:9C800ACA 2000-10-19 SUSE Package Signing Key <[email protected]>
Key fingerprint = 79C1 79B2 E1C8 20C1 890F 9994 A84E DAE8 9C80 0ACA
The command rpm --checksig package.rpm shows whether the checksum
and the signature of an uninstalled package are correct. Find the key on the first
CD of the distribution and on most key servers worldwide.
• Check your backups of user and system files regularly. Consider that if you do not
test whether the backup works, it might actually be worthless.
• Check your log files. Whenever possible, write a small script to search for suspicious
entries. Admittedly, this is not exactly a trivial task. In the end, only you can know
which entries are unusual and which are not.
• Use tcp_wrapper to restrict access to the individual services running on your
machine, so you have explicit control over which IP addresses can connect to a
Security in Linux
339
service. For further information regarding tcp_wrapper, consult the manual
pages of tcpd and hosts_access (man 8 tcpd, man hosts_access).
• Use SuSEfirewall to enhance the security provided by tcpd (tcp_wrapper).
• Design your security measures to be redundant: a message seen twice is much
better than no message at all.
23.4.3 Using the Central Security Reporting
Address
If you discover a security-related problem (please check the available update packages
first), write an e-mail to [email protected] Please include a detailed description
of the problem and the version number of the package concerned. SUSE will try to send
a reply as soon as possible. You are encouraged to pgp encrypt your e-mail messages.
SUSE's pgp key is:
ID:3D25D3D9 1999-03-06 SUSE Security Team <[email protected]>
Key fingerprint = 73 5F 2E 99 DF DB 94 C4 8F 5A A3 AE AF 22 F2 D5
This key is also available for download from http://www.novell.com/linux/
security/securitysupport.html.
340
Access Control Lists in Linux
24
This chapter provides a brief summary of the background and functions of POSIX
ACLs (access control lists) for Linux file systems. ACLs can be used as an expansion
of the traditional permission concept for file system objects. With ACLs, permissions
can be defined more flexibly than the traditional permission concept allows.
The term POSIX ACL suggests that this is a true POSIX (portable operating system
interface) standard. The respective draft standards POSIX 1003.1e and POSIX 1003.2c
have been withdrawn for several reasons. Nevertheless, ACLs as found on many systems
belonging to the UNIX family are based on these drafts and the implementation of file
system ACLs as described in this chapter follows these two standards as well. They
can be viewed at http://wt.xpilot.org/publications/posix.1e/.
24.1
Advantages of ACLs
Traditionally, three sets of permissions are defined for each file object on a Linux system.
These sets include the read (r), write (w), and execute (x) permissions for each of three
types of users—the file owner, the group, and other users. In addition to that, it is possible to set the set user id, the set group id, and the sticky bit. This lean concept is fully
adequate for most practical cases. However, for more complex scenarios or advanced
applications, system administrators formerly had to use a number of tricks to circumvent
the limitations of the traditional permission concept.
ACLs can be used for situations that require an extension of the traditional file permission concept. They allow assignment of permissions to individual users or groups even
if these do not correspond to the original owner or the owning group. Access control
Access Control Lists in Linux
341
lists are a feature of the Linux kernel and are currently supported by ReiserFS, Ext2,
Ext3, JFS, and XFS. Using ACLs, complex scenarios can be realized without implementing complex permission models on the application level.
The advantages of ACLs are clearly evident in a situation like replacement of a Windows
server with a Linux server. Some of the connected workstations may continue to run
under Windows even after the migration. The Linux system offers file and print services
to the Windows clients with Samba. Given that Samba supports access control lists,
user permissions can be configured both on the Linux server and in Windows with a
graphical user interface (only Windows NT and later). With winbindd, it is even possible
to assign permissions to users that only exist in the Windows domain without any account
on the Linux server.
24.2
Definitions
user class
The conventional POSIX permission concept uses three classes of users for assigning
permissions in the file system: the owner, the owning group, and other users. Three
permission bits can be set for each user class, giving permission to read (r), write
(w), and execute (x).
access ACL
The user and group access permissions for all kinds of file system objects (files and
directories) are determined by means of access ACLs.
default ACL
Default ACLs can only be applied to directories. They determine the permissions
a file system object inherits from its parent directory when it is created.
ACL entry
Each ACL consists of a set of ACL entries. An ACL entry contains a type (see Table 24.1, “ACL Entry Types” (page 343)), a qualifier for the user or group to which
the entry refers, and a set of permissions. For some entry types, the qualifier for the
group or users is undefined.
342
24.3
Handling ACLs
Table 24.1, “ACL Entry Types” (page 343) summarizes the six possible types of ACL
entries, each defining permissions for a user or a group of users. The owner entry defines
the permissions of the user owning the file or directory. The owning group entry defines
the permissions of the file's owning group. The superuser can change the owner or
owning group with chown or chgrp, in which case the owner and owning group entries
refer to the new owner and owning group. Each named user entry defines the permissions
of the user specified in the entry's qualifier field, which is the middle field in the text
form shown in Table 24.1, “ACL Entry Types” (page 343). Each named group entry
defines the permissions of the group specified in the entry's qualifier field. Only the
named user and named group entries have a qualifier field that is not empty. The other
entry defines the permissions of all other users.
The mask entry further limits the permissions granted by named user, named group,
and owning group entries by defining which of the permissions in those entries are effective and which are masked. If permissions exist in one of the mentioned entries as
well as in the mask, they are effective. Permissions contained only in the mask or only
in the actual entry are not effective—meaning the permissions are not granted. All
permissions defined in the owner and owning group entries are always effective. The
example in Table 24.2, “Masking Access Permissions” (page 344) demonstrates this
mechanism.
There are two basic classes of ACLs: A minimum ACL contains only the entries for
the types owner, owning group, and other, which correspond to the conventional permission bits for files and directories. An extended ACL goes beyond this. It must contain
a mask entry and may contain several entries of the named user and named group types.
Table 24.1
ACL Entry Types
Type
Text Form
owner
user::rwx
named user
user:name:rwx
owning group
group::rwx
named group
group:name:rwx
Access Control Lists in Linux
343
Type
Text Form
mask
mask::rwx
other
other::rwx
Table 24.2
Masking Access Permissions
Entry Type
Text Form
Permissions
named user
user:geeko:r-x
r-x
mask
mask::rw-
rw-
effective permissions:
r--
24.3.1 ACL Entries and File Mode
Permission Bits
Figure 24.1, “Minimum ACL: ACL Entries Compared to Permission Bits” (page 345)
and Figure 24.2, “Extended ACL: ACL Entries Compared to Permission Bits” (page 345)
illustrate the two cases of a minimum ACL and an extended ACL. The figures are
structured in three blocks—the left block shows the type specifications of the ACL
entries, the center block displays an example ACL, and the right block shows the respective permission bits according to the conventional permission concept, for example,
as displayed by ls -l. In both cases, the owner class permissions are mapped to the
ACL entry owner. Other class permissions are mapped to the respective ACL entry.
However, the mapping of the group class permissions is different in the two cases.
344
Figure 24.1
Minimum ACL: ACL Entries Compared to Permission Bits
In the case of a minimum ACL—without mask—the group class permissions are mapped
to the ACL entry owning group. This is shown in Figure 24.1, “Minimum ACL: ACL
Entries Compared to Permission Bits” (page 345). In the case of an extended ACL—with
mask—the group class permissions are mapped to the mask entry. This is shown in
Figure 24.2, “Extended ACL: ACL Entries Compared to Permission Bits” (page 345).
Figure 24.2
Extended ACL: ACL Entries Compared to Permission Bits
This mapping approach ensures the smooth interaction of applications, regardless of
whether they have ACL support. The access permissions that were assigned by means
of the permission bits represent the upper limit for all other “fine adjustments” made
with an ACL. Changes made to the permission bits are reflected by the ACL and vice
versa.
24.3.2 A Directory with an Access ACL
The handling of access ACLs is demonstrated in the following example:
Before you create the directory, use the umask command to define which access permissions should be masked each time a file object is created. The command umask
027 sets the default permissions by giving the owner the full range of permissions (0),
Access Control Lists in Linux
345
denying the group write access (2), and giving other users no permissions at all (7).
umask actually masks the corresponding permission bits or turns them off. For details,
consult the corresponding man page (man umask).
mkdir mydir should create the mydir directory with the default permissions as set
by umask. Use ls -dl mydir to check if all permissions were assigned correctly.
The output for this example is:
drwxr-x--- ... tux project3 ... mydir
With getfacl mydir, check the initial state of the ACL. This gives information
like:
# file: mydir
# owner: tux
# group: project3
user::rwx
group::r-x
other::---
The output of getfacl precisely reflects the mapping of permission bits and ACL
entries as described in Section 24.3.1, “ACL Entries and File Mode Permission Bits”
(page 344). The first three output lines display the name, owner, and owning group of
the directory. The next three lines contain the three ACL entries owner, owning group,
and other. In fact, in the case of this minimum ACL, the getfacl command does not
produce any information you could not have obtained with ls.
Modify the ACL to assign read, write, and execute permissions to an additional user
geeko and an additional group mascots with:
setfacl -m user:geeko:rwx,group:mascots:rwx mydir
The option -m prompts setfacl to modify the existing ACL. The following argument
indicates the ACL entries to modify (multiple entries are separated by commas). The
final part specifies the name of the directory to which these modifications should be
applied. Use the getfacl command to take a look at the resulting ACL.
# file: mydir
# owner: tux
# group: project3
user::rwx
user:geeko:rwx
group::r-x
group:mascots:rwx
mask::rwx
other::---
346
In addition to the entries initiated for the user geeko and the group mascots, a mask
entry has been generated. This mask entry is set automatically so that all permissions
are effective. setfacl automatically adapts existing mask entries to the settings
modified, unless you deactivate this feature with -n. mask defines the maximum effective access permissions for all entries in the group class. This includes named user,
named group, and owning group. The group class permission bits displayed by ls -dl
mydir now correspond to the mask entry.
drwxrwx---+ ... tux project3 ... mydir
The first column of the output now contains an additional + to indicate that there is an
extended ACL for this item.
According to the output of the ls command, the permissions for the mask entry include
write access. Traditionally, such permission bits would mean that the owning group
(here project3) also has write access to the directory mydir. However, the effective
access permissions for the owning group correspond to the overlapping portion of the
permissions defined for the owning group and for the mask—which is r-x in our example (see Table 24.2, “Masking Access Permissions” (page 344)). As far as the effective
permissions of the owning group in this example are concerned, nothing has changed
even after the addition of the ACL entries.
Edit the mask entry with setfacl or chmod. For example, use chmod g-w mydir.
ls -dl mydir then shows:
drwxr-x---+ ... tux project3 ... mydir
getfacl mydir provides the following output:
# file: mydir
# owner: tux
# group: project3
user::rwx
user:geeko:rwx
group::r-x
group:mascots:rwx
mask::r-x
other::---
# effective: r-x
# effective: r-x
After executing the chmod command to remove the write permission from the group
class bits, the output of the ls command is sufficient to see that the mask bits must
have changed accordingly: write permission is again limited to the owner of mydir.
The output of the getfacl confirms this. This output includes a comment for all those
entries in which the effective permission bits do not correspond to the original permis-
Access Control Lists in Linux
347
sions, because they are filtered according to the mask entry. The original permissions
can be restored at any time with chmod g+w mydir.
24.3.3 A Directory with a Default ACL
Directories can have a default ACL, which is a special kind of ACL defining the access
permissions that objects in the directory inherit when they are created. A default ACL
affects both subdirectories and files.
Effects of a Default ACL
There are two different ways in which the permissions of a directory's default ACL are
passed to the files and subdirectories in it:
• A subdirectory inherits the default ACL of the parent directory both as its default
ACL and as an access ACL.
• A file inherits the default ACL as its access ACL.
All system calls that create file system objects use a mode parameter that defines the
access permissions for the newly created file system object. If the parent directory does
not have a default ACL, the permission bits as defined by the umask are subtracted
from the permissions as passed by the mode parameter, with the result being assigned
to the new object. If a default ACL exists for the parent directory, the permission bits
assigned to the new object correspond to the overlapping portion of the permissions of
the mode parameter and those that are defined in the default ACL. The umask is disregarded in this case.
Application of Default ACLs
The following three examples show the main operations for directories and default
ACLs:
1.
Add a default ACL to the existing directory mydir with:
setfacl -d -m group:mascots:r-x mydir
The option -d of the setfacl command prompts setfacl to perform the
following modifications (option -m) in the default ACL.
348
Take a closer look at the result of this command:
getfacl mydir
# file: mydir
# owner: tux
# group: project3
user::rwx
user:geeko:rwx
group::r-x
group:mascots:rwx
mask::rwx
other::--default:user::rwx
default:group::r-x
default:group:mascots:r-x
default:mask::r-x
default:other::---
getfacl returns both the access ACL and the default ACL. The default ACL
is formed by all lines that start with default. Although you merely executed
the setfacl command with an entry for the mascots group for the default
ACL, setfacl automatically copied all other entries from the access ACL to
create a valid default ACL. Default ACLs do not have an immediate effect on
access permissions. They only come into play when file system objects are created. These new objects inherit permissions only from the default ACL of their
parent directory.
2.
In the next example, use mkdir to create a subdirectory in mydir, which inherits
the default ACL.
mkdir mydir/mysubdir
getfacl mydir/mysubdir
# file: mydir/mysubdir
# owner: tux
# group: project3
user::rwx
group::r-x
group:mascots:r-x
mask::r-x
other::--default:user::rwx
default:group::r-x
default:group:mascots:r-x
default:mask::r-x
default:other::---
Access Control Lists in Linux
349
As expected, the newly-created subdirectory mysubdir has the permissions
from the default ACL of the parent directory. The access ACL of mysubdir
is an exact reflection of the default ACL of mydir. The default ACL that this
directory will hand down to its subordinate objects is also the same.
3.
Use touch to create a file in the mydir directory, for example, touch
mydir/myfile. ls -l mydir/myfile then shows:
-rw-r-----+ ... tux project3 ... mydir/myfile
The output of getfacl mydir/myfile is:
# file: mydir/myfile
# owner: tux
# group: project3
user::rwgroup::r-x
# effective:r-group:mascots:r-x
# effective:r-mask::r-other::---
touch uses a mode with the value 0666 when creating new files, which means
that the files are created with read and write permissions for all user classes,
provided no other restrictions exist in umask or in the default ACL (see Section
“Effects of a Default ACL” (page 348)). In effect, this means that all access permissions not contained in the mode value are removed from the respective ACL
entries. Although no permissions were removed from the ACL entry of the group
class, the mask entry was modified to mask permissions not set in mode.
This approach ensures the smooth interaction of applications, such as compilers,
with ACLs. You can create files with restricted access permissions and subsequently mark them as executable. The mask mechanism guarantees that the
right users and groups can execute them as desired.
24.3.4 The ACL Check Algorithm
A check algorithm is applied before any process or application is granted access to an
ACL-protected file system object. As a basic rule, the ACL entries are examined in the
following sequence: owner, named user, owning group or named group, and other. The
access is handled in accordance with the entry that best suits the process. Permissions
do not accumulate.
350
Things are more complicated if a process belongs to more than one group and would
potentially suit several group entries. An entry is randomly selected from the suitable
entries with the required permissions. It is irrelevant which of the entries triggers the
final result “access granted”. Likewise, if none of the suitable group entries contains
the required permissions, a randomly selected entry triggers the final result “access
denied”.
24.4
ACL Support in Applications
ACLs can be used to implement very complex permission scenarios that meet the requirements of modern applications. The traditional permission concept and ACLs can
be combined in a smart manner. The basic file commands (cp, mv, ls, etc.) support
ACLs, as does Samba.
Unfortunately, many editors and file managers still lack ACL support. When copying
files with Konqueror, for instance, the ACLs of these files are lost. When modifying
files with an editor, the ACLs of files are sometimes preserved and sometimes not, depending on the backup mode of the editor used. If the editor writes the changes to the
original file, the access ACL is preserved. If the editor saves the updated contents to a
new file that is subsequently renamed to the old filename, the ACLs may be lost, unless
the editor supports ACLs. Except for the star archiver, there are currently no backup
applications that preserve ACLs.
24.5
For More Information
Detailed information about ACLs is available at http://acl.bestbits.at/.
Also see the man pages for getfacl(1), acl(5), and setfacl(1).
Access Control Lists in Linux
351
System Monitoring Utilities
25
A number of programs and mechanisms, some of which are presented here, can be used
to examine the status of your system. Also described are some utilities that are useful
for routine work, along with their most important parameters.
For each of the commands introduced, examples of the relevant outputs are presented.
In these examples, the first line is the command itself (after the dollar sign prompt).
Omissions are indicated with square brackets ([...]) and long lines are wrapped
where necessary. Line breaks for long lines are indicated by a backslash (\).
$ command -x -y
output line 1
output line 2
output line 3 is annoyingly long, so long that \
we have to break it
output line 3
[...]
output line 98
output line 99
The descriptions have been kept short to allow as many utilities as possible to be mentioned. Further information for all the commands can be found in the man pages. Most
of the commands also understand the parameter --help, which produces a brief list
of the possible parameters.
25.1
List of Open Files: lsof
To view a list of all the files open for the process with process ID PID, use -p. For
example, to view all the files used by the current shell, enter:
System Monitoring Utilities
353
$ lsof -p $$
COMMAND PID USER
FD
TYPE DEVICE
SIZE
NODE NAME
zsh
4694
jj cwd
DIR
0,18
144 25487368 /suse/jj/t
(totan:/real-home/jj)
zsh
4694
jj rtd
DIR
3,2
608
2 /
zsh
4694
jj txt
REG
3,2 441296
20414 /bin/zsh
zsh
4694
jj mem
REG
3,2 104484
10882 /lib/ld-2.3.3.so
zsh
4694
jj mem
REG
3,2
11648
20610
/usr/lib/zsh/4.2.0/zsh/rlimits.so
[...]
zsh
4694
jj mem
REG
3,2
13647
10891 /lib/libdl.so.2
zsh
4694
jj mem
REG
3,2
88036
10894 /lib/libnsl.so.1
zsh
4694
jj mem
REG
3,2 316410
147725 /lib/libncurses.so.5.4
zsh
4694
jj mem
REG
3,2 170563
10909 /lib/tls/libm.so.6
zsh
4694
jj mem
REG
3,2 1349081
10908 /lib/tls/libc.so.6
zsh
4694
jj mem
REG
3,2
56
12410
/usr/lib/locale/de_DE.utf8/LC_TELEPHONE
[...]
zsh
4694
jj mem
REG
3,2
59
14393
/usr/lib/locale/en_US/LC_NUMERIC
zsh
4694
jj mem
REG
3,2 178476
14565
/usr/lib/locale/en_US/LC_CTYPE
zsh
4694
jj mem
REG
3,2
56444
20598
/usr/lib/zsh/4.2.0/zsh/computil.so
zsh
4694
jj
0u
CHR 136,48
50 /dev/pts/48
zsh
4694
jj
1u
CHR 136,48
50 /dev/pts/48
zsh
4694
jj
2u
CHR 136,48
50 /dev/pts/48
zsh
4694
jj
10u
CHR 136,48
50 /dev/pts/48
The special shell variable $$, whose value is the process ID of the shell, has been used.
The command lsof lists all the files currently open when used without any parameters.
Because there are often thousands of open files, listing all of them is rarely useful.
However, the list of all files can be combined with search functions to generate useful
lists. For example, list all used character devices:
$ lsof | grep CHR
sshd
4685
sshd
4685
sshd
4693
sshd
4693
zsh
4694
zsh
4694
zsh
4694
zsh
4694
X
6476
lsof
13478
lsof
13478
grep
13480
grep
13480
354
root
root
jj
jj
jj
jj
jj
jj
root
jj
jj
jj
jj
mem
mem
mem
mem
0u
1u
2u
10u
mem
0u
2u
1u
2u
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
CHR
1,5
1,5
1,5
1,5
136,48
136,48
136,48
136,48
1,1
136,48
136,48
136,48
136,48
45833
45833
45833
45833
50
50
50
50
38042
50
50
50
50
/dev/zero
/dev/zero
/dev/zero
/dev/zero
/dev/pts/48
/dev/pts/48
/dev/pts/48
/dev/pts/48
/dev/mem
/dev/pts/48
/dev/pts/48
/dev/pts/48
/dev/pts/48
25.2
User Accessing Files: fuser
It can be useful to determine what processes or users are currently accessing certain
files. Suppose, for example, you want to unmount a file system mounted at /mnt.
umount returns "device is busy." The command fuser can then be used to determine
what processes are accessing the device:
$ fuser -v /mnt/*
USER
PID ACCESS COMMAND
/mnt/notes.txt
jj
26597 f....
less
Following termination of the less process, which was running on another terminal,
the file system can successfully be unmounted.
25.3
File Properties: stat
The command stat displays file properties:
$ stat xml-doc.txt
File: `xml-doc.txt'
Size: 632
Blocks: 8
IO Block: 4096
Device: eh/14d Inode: 5938009
Links: 1
Access: (0644/-rw-r--r--) Uid: (11994/
jj)
Gid: (
Access: 2004-04-27 20:08:58.000000000 +0200
Modify: 2003-06-03 15:29:34.000000000 +0200
Change: 2003-07-23 17:48:27.000000000 +0200
regular file
50/
suse)
The parameter --filesystem produces details of the properties of the file system
in which the specified file is located:
$ stat
File:
ID:
Blocks:
Inodes:
. --filesystem
"."
0
Namelen: 255
Type: ext2/ext3
Total: 19347388
Free: 17831731
Available: 16848938
Total: 9830400
Free: 9663967
Size: 4096
If you use the z shell (zsh), you must enter /usr/bin/stat, because the z shell
has a shell built-in stat with different options and a different output format:
% type stat
stat is a shell builtin
% stat .
System Monitoring Utilities
355
device
inode
mode
nlink
uid
gid
rdev
size
atime
mtime
ctime
blksize
blocks
link
769
4554808
16877
12
11994
50
0
4096
1091536882
1091535740
1091535740
4096
8
25.4
USB Devices: lsusb
The command lsusb lists all USB devices. With the option -v, print a more detailed
list. The detailed information is read from the directory /proc/bus/usb/. The following is the output of lsusb after a USB memory stick was attached. The last lines
indicate the presence of the new device.
Bus
Bus
Bus
Bus
Bus
004
003
002
001
001
Device
Device
Device
Device
Device
25.5
001:
001:
001:
001:
018:
ID
ID
ID
ID
ID
0000:0000
0000:0000
0000:0000
0000:0000
0402:5634 ALi Corp.
Information about a SCSI
Device: scsiinfo
The command scsiinfo lists information about a SCSI device. With the option -l,
list all SCSI devices known to the system (similar information is obtained via the
command lsscsi). The following is the output of scsiinfo -i /dev/sda,
which gives information about a hard disk. The option -a gives even more information.
Inquiry command
--------------Relative Address
Wide bus 32
Wide bus 16
Synchronous neg.
Linked Commands
356
0
0
1
1
1
Command Queueing
SftRe
Device Type
Peripheral Qualifier
Removable?
Device Type Modifier
ISO Version
ECMA Version
ANSI Version
AENC
TrmIOP
Response Data Format
Vendor:
Product:
Revision level:
1
0
0
0
0
0
0
0
3
0
0
2
FUJITSU
MAS3367NP
0104A0K7P43002BE
There is a defects list with two tables of bad blocks of a hard disk: first the one supplied
by the vendor (manufacturer table) and second the list of bad blocks that appeared in
operation (grown table). If the number of entries in the grown table increases, it might
be a good idea to replace the hard disk.
25.6
Processes: top
The command top, which stands for "table of processes," displays a list of processes
that is refreshed every two seconds. To terminate the program, press Q . The parameter
-n 1 terminates the program after a single display of the process list. The following
is an example output of the command top -n 1:
top - 14:19:53 up 62 days, 3:35, 14 users, load average: 0.01, 0.02, 0.00
Tasks: 102 total,
7 running, 93 sleeping,
0 stopped,
2 zombie
Cpu(s):
0.3% user,
0.1% system,
0.0% nice, 99.6% idle
Mem:
514736k total,
497232k used,
17504k free,
56024k buffers
Swap: 1794736k total,
104544k used, 1690192k free,
235872k cached
PID
1426
20836
1
2
3
4
5
USER
root
jj
root
root
root
root
root
[...]
1362 root
1363 root
1377 root
PR
15
15
15
15
34
15
15
NI
0
0
0
0
19
0
0
VIRT
116m
820
100
0
0
0
0
RES
41m
820
96
0
0
0
0
SHR
18m
612
72
0
0
0
0
S %CPU %MEM
S 1.0 8.2
R 1.0 0.2
S 0.0 0.0
S 0.0 0.0
S 0.0 0.0
S 0.0 0.0
S 0.0 0.0
15
15
17
0
0
0
488
488
56
452
452
4
404 S
404 S
4 S
0.0
0.0
0.0
0.1
0.1
0.0
TIME+
82:30.34
0:00.03
0:08.43
0:04.96
0:00.99
0:33.63
0:00.71
Command
X
top
init
keventd
ksoftirqd_CPU0
kswapd
bdflush
0:00.02 nscd
0:00.04 nscd
0:00.00 mingetty
System Monitoring Utilities
357
1379 root
1380 root
18
18
0
0
56
56
4
4
4 S
4 S
0.0
0.0
0.0
0.0
0:00.01 mingetty
0:00.01 mingetty
If you press F while top is running, a menu opens with which to make extensive
changes to the format of the output.
The parameter -U UID monitors only the processes associated with a particular user.
Replace UID with the user ID of the user. top -U $(id -u username) returns
the UID of the user on the basis of the username and displays his processes.
25.7
Process List: ps
The command ps produces a list of processes. If the parameter r is added, only processes currently using computing time are shown:
$ ps r
PID TTY
22163 pts/7
3396 pts/3
20027 pts/7
20974 pts/7
27454 pts/7
STAT
R
R
R
R
R
TIME
0:01
0:03
0:25
0:01
0:00
COMMAND
-zsh
emacs new-makedoc.txt
emacs xml/common/utilities.xml
emacs jj.xml
ps r
This parameter must be written without a minus sign. The various parameters are
written sometimes with and sometimes without the minus sign. The man page could
easily frighten off potential users, but fortunately the ps --help command produces
a brief page of help.
To check how many emacs processes are running, use:
$ ps x | grep emacs
1288 ?
S
3396 pts/3
S
3475 ?
S
20027 pts/7
S
20974 pts/7
S
0:07
0:04
0:03
0:40
0:02
emacs
emacs
emacs
emacs
emacs
new-makedoc.txt
.Xresources
xml/common/utilities.xml
jj.xml
$ pidof emacs
20974 20027 3475 3396 1288
The parameter -p selects processes via the process ID:
$ ps www -p $(pidof xterm)
PID TTY
STAT
TIME COMMAND
9025 ?
S
0:01 xterm -g 100x45+0+200
9176 ?
S
0:00 xterm -g 100x45+0+200
358
29854 ?
S
0:21 xterm -g 100x75+20+0 -fn \
-B&H-LucidaTypewriter-Medium-R-Normal-Sans-12-120-75-75-M-70-iso10646-1
4378 ?
S
0:01 xterm -bg MistyRose1 -T root -n root -e su -l
25543 ?
S
0:02 xterm -g 100x45+0+200
22161 ?
R
0:14 xterm -g 100x45+0+200
16832 ?
S
0:01 xterm -bg MistyRose1 -T root -n root -e su -l
16912 ?
S
0:00 xterm -g 100x45+0+200
17861 ?
S
0:00 xterm -bg DarkSeaGreen1 -g 120x45+40+300
19930 ?
S
0:13 xterm -bg LightCyan
21686 ?
S
0:04 xterm -g 100x45+0+200 -fn \
lucidasanstypewriter-12
23104 ?
S
0:00 xterm -g 100x45+0+200
26547 ?
S
0:00 xterm -g 100x45+0+200
The process list can be formatted according to your needs. The option -L returns a list
of all keywords. Enter the following command to issue a list of all processes sorted by
memory usage:
$ ps ax --format pid,rss,cmd --sort rss
PID RSS CMD
2
0 [ksoftirqd/0]
3
0 [events/0]
17
0 [kblockd/0]
[...]
10164 5260 xterm
31110 5300 xterm
17010 5356 xterm
3896 29292 /usr/X11R6/bin/X -nolisten tcp -br vt7 -auth
/var/lib/xdm/authdir/au
25.8
Process Tree: pstree
The command pstree produces a list of processes in the form of a tree:
$ pstree
init-+-atd
|-3*[automount]
|-bdflush
|-cron
[...]
|-usb-storage-1
|-usb-storage-2
|-10*[xterm---zsh]
|-xterm---zsh---mutt
|-2*[xterm---su---zsh]
|-xterm---zsh---ssh
|-xterm---zsh---pstree
|-ypbind---ypbind---2*[ypbind]
`-zsh---startx---xinit4-+-X
System Monitoring Utilities
359
`-ctwm-+-xclock
|-xload
`-xosview.bin
The parameter -p adds the process ID to a given name. To have the command lines
displayed as well, use the -a parameter:
$ pstree -pa
init,1
|-atd,1255
[...]
`-zsh,1404
`-startx,1407 /usr/X11R6/bin/startx
`-xinit4,1419 /suse/jj/.xinitrc [...]
|-X,1426 :0 -auth /suse/jj/.Xauthority
`-ctwm,1440
|-xclock,1449 -d -geometry -0+0 -bg grey
|-xload,1450 -scale 2
`-xosview.bin,1451 +net -bat +net
25.9
Who Is Doing What: w
With the command w, find out who is logged onto the system and what each user is
doing. For example:
$ w
15:17:26 up 62 days, 4:33, 14 users, load average: 0.00, 0.04, 0.01
USER
TTY
[email protected]
IDLE
JCPU
PCPU WHAT
jj
pts/0
30Mar04 4days 0.50s 0.54s xterm -e su -l
jj
pts/1
23Mar04 5days 0.20s 0.20s -zsh
jj
pts/2
23Mar04 5days 1.28s 1.28s -zsh
jj
pts/3
23Mar04 3:28m 3.21s 0.50s -zsh
[...]
jj
pts/7
07Apr04 0.00s 9.02s 0.01s w
jj
pts/9
25Mar04 3:24m 7.70s 7.38s mutt
[...]
jj
pts/14
12:49
37:34
0.20s 0.13s ssh totan
The last line shows that the user jj has established a secure shell (ssh) connection to
the computer totan. If any users of other systems have logged in remotely, the parameter -f shows the computers from which they have established the connection.
360
25.10
Memory Usage: free
The utility free examines RAM usage. Details of both free and used memory (and
swap areas) are shown:
$ free
total
Mem:
514736
-/+ buffers/cache:
Swap:
1794736
used
273964
195716
104096
free
240772
319020
1690640
shared
0
buffers
35920
cached
42328
shared
0
buffers
35
cached
41
With -m, all sizes are expressed in megabytes:
$ free -m
total
Mem:
502
-/+ buffers/cache:
Swap:
1752
used
267
191
101
free
235
311
1651
The really interesting information is contained in the following line:
-/+ buffers/cache:
191
311
This calculates the amount of memory taken up with buffers and caches. The parameter
-d delay ensures that the display is refreshed every delay seconds. For example,
free -d 1.5 produces an update every 1.5 seconds.
25.11
Kernel Ring Buffer: dmesg
The Linux kernel keeps certain messages in a ring buffer. To view these messages,
enter the command dmesg:
$ dmesg
[...]
sdc : READ CAPACITY failed.
sdc : status = 1, message = 00, host = 0, driver = 08
Info fld=0xa00 (nonstd), Current sd00:00: sense key Not Ready
sdc : block size assumed to be 512 bytes, disk size 1GB.
sdc: test WP failed, assume Write Enabled
sdc: I/O error: dev 08:20, sector 0
I/O error: dev 08:20, sector 0
I/O error: dev 08:20, sector 2097144
I/O error: dev 08:20, sector 2097144
I/O error: dev 08:20, sector 0
I/O error: dev 08:20, sector 0
unable to read partition table
System Monitoring Utilities
361
I/O error: dev 08:20, sector 0
nfs: server totan not responding, still trying
nfs: server totan OK
The last line indicates that there is a temporary problem in the NFS server totan. The
lines up to that point are triggered by the insertion of a USB flash drive. Older events
are logged in the files /var/log/messages and /var/log/warn.
25.12
File Systems and Their Usage:
mount, df, and du
The command mount shows which file system (device and type) is mounted at which
mount point:
$ mount
/dev/hdb2 on / type ext2 (rw)
proc on /proc type proc (rw)
devpts on /dev/pts type devpts (rw,mode=0620,gid=5)
/dev/hda1 on /data type ext2 (rw)
shmfs on /dev/shm type shm (rw)
usbdevfs on /proc/bus/usb type usbdevfs (rw)
automount(pid1012) on /suse type autofs \
(rw,fd=5,pgrp=1012,minproto=2,maxproto=3)
totan:/real-home/jj on /suse/jj type nfs \
(rw,nosuid,rsize=8192,wsize=8192,hard,intr,nolock,addr=10.10.0.1)
Obtain information about total usage of the file systems with the command df. The
parameter -h (or --human-readable) transforms the output into a form understandable for common users.
$ df -h
Filesystem
/dev/hdb2
/dev/hda1
shmfs
totan:/real-home/jj
Size
7.4G
74G
252M
350G
Used Avail Use% Mounted on
5.1G 2.0G 73% /
5.8G
65G
9% /data
0 252M
0% /dev/shm
324G
27G 93% /suse/jj
Users of the NFS file server totan should clear their home directory without delay.
Display the total size of all the files in a given directory and its subdirectories with the
command du. The parameter -s suppresses the output of detailed information. -h
again transforms the data into a form that ordinary people can understand. With this
command:
362
$ du -sh ~
361M
/suse/jj
see how much space your own home directory occupies.
25.13
The /proc File System
The /proc file system is a pseudo file system in which the kernel reserves important
information in the form of virtual files. For example, display the CPU type with this
command:
$ cat /proc/cpuinfo
processor
: 0
vendor_id
: AuthenticAMD
cpu family
: 6
model
: 8
model name
: AMD Athlon(tm) XP 2400+
stepping
: 1
cpu MHz
: 2009.343
cache size
: 256 KB
fdiv_bug
: no
[...]
The allocation and use of interrupts can be queried with the following command:
$ cat /proc/interrupts
CPU0
0: 537544462
1:
820082
2:
0
8:
2
9:
0
10:
13970
11: 146467509
12:
8061393
14:
2465743
15:
1355
NMI:
0
LOC:
0
ERR:
0
MIS:
0
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
XT-PIC
timer
keyboard
cascade
rtc
acpi
usb-uhci, usb-uhci
ehci_hcd, usb-uhci, eth0
PS/2 Mouse
ide0
ide1
Some of the important files and their contents are:
/proc/devices
available devices
System Monitoring Utilities
363
/proc/modules
kernel modules loaded
/proc/cmdline
kernel command line
/proc/meminfo
detailed information about memory usage
/proc/config.gz
gzip-compressed configuration file of the kernel currently running
Further information is available in the text file /usr/src/linux/
Documentation/filesystems/proc.txt. Information about processes currently running can be found in the /proc/NNN directories, where NNN is the process
ID (PID) of the relevant process. Every process can find its own characteristics in
/proc/self/:
$ ls -l /proc/self
lrwxrwxrwx 1 root root 64 Apr 29 13:52 /proc/self -> 27585
$ ls -l /proc/self/
total 0
dr-xr-xr-x 2 jj suse
-r-------- 1 jj suse
-r--r--r-- 1 jj suse
lrwxrwxrwx 1 jj suse
-r--r--r-- 1 jj suse
-r-------- 1 jj suse
lrwxrwxrwx 1 jj suse
dr-x------ 2 jj suse
-rw------- 1 jj suse
-r--r--r-- 1 jj suse
-rw------- 1 jj suse
-r--r--r-- 1 jj suse
lrwxrwxrwx 1 jj suse
-r--r--r-- 1 jj suse
-r--r--r-- 1 jj suse
-r--r--r-- 1 jj suse
dr-xr-xr-x 3 jj suse
-r--r--r-- 1 jj suse
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
29
29
29
29
29
29
29
29
29
29
29
29
29
29
29
29
29
29
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
13:52
attr
auxv
cmdline
cwd -> /suse/jj/t
delay
environ
exe -> /bin/ls
fd
mapped_base
maps
mem
mounts
root -> /
stat
statm
status
task
wchan
The address assignment of executables and libraries is contained in the maps file:
$ cat /proc/self/maps
08048000-0804c000 r-xp 00000000 03:02 22890
0804c000-0804d000 rw-p 00003000 03:02 22890
0804d000-0806e000 rwxp 0804d000 00:00 0
364
/bin/cat
/bin/cat
40000000-40016000
40016000-40017000
40017000-40018000
4002b000-40135000
40135000-4013d000
4013d000-40141000
bfffe000-c0000000
ffffe000-fffff000
25.14
r-xp
rw-p
rw-p
r-xp
rw-p
rw-p
rw-p
---p
00000000
00015000
40017000
00000000
0010a000
4013d000
bfffe000
00000000
03:02
03:02
00:00
03:02
03:02
00:00
00:00
00:00
10882
10882
0
10908
10908
0
0
0
/lib/ld-2.3.3.so
/lib/ld-2.3.3.so
/lib/tls/libc.so.6
/lib/tls/libc.so.6
vmstat, iostat, and mpstat
The utility vmstat reports virtual memory statistics. It reads the files /proc/
meminfo, /proc/stat, and /proc/*/stat. It is useful to identify bottlenecks
of the system performance. The command iostat reports statistics about the CPU
and input and output for devices and partitions. The displayed information is taken from
the files /proc/stat and /proc/partitions. The output can be used to better
balance the input and output load between hard disks. The command mpstat reports
CPU-related statistics.
25.15
procinfo
Important information from the /proc file system is summarized by the command
procinfo:
$ procinfo
Linux 2.6.4-54.5-default ([email protected]) (gcc 3.3.3 ) #1 1CPU [roth.suse.de]
Memory:
Mem:
Swap:
Total
516696
530136
Bootup: Wed Jul
user :
nice :
system:
idle :
uptime:
Used
513200
1352
7 14:29:08 2004
2:42:28.08
0:31:57.13
0:38:32.23
3d 19:26:05.93
4d 0:22:25.84
1.3%
0.2%
0.3%
97.7%
Free
3496
528784
Shared
0
Buffers
43284
Load average: 0.07 0.04 0.01 1/126 5302
page in :
0
page out:
0
swap in :
0
swap out:
0
context :207939498
irq
0: 776561217 timer
irq
8:
2 rtc
irq
1:
irq
9:
24300 VIA8233
276048 i8042
System Monitoring Utilities
365
irq
2:
0 cascade [4]
irq 11:
38610118 acpi, eth0, uhci_hcd
irq
3:
3
irq 12:
3435071 i8042
irq
4:
3
irq 14:
2236471 ide0
irq
6:
2
irq 15:
251 ide1
To see all the information, use the parameter -a. The parameter -nN produces updates
of the information every N seconds. In this case, terminate the program by pressing Q .
By default, the cumulative values are displayed. The parameter -d produces the differential values. procinfo -dn5 displays the values that have changed in the last five
seconds:
Memory:
Mem:
Swap:
Total
0
0
Used
2
0
Bootup: Wed Feb 25 09:44:17 2004
user :
nice :
system:
idle :
uptime:
irq
irq
irq
irq
irq
irq
64d
0:
1:
2:
6:
8:
9:
25.16
0:00:00.02
0:00:00.00
0:00:00.00
0:00:04.99
3:59:12.62
501
1
0
0
0
0
0.4%
0.0%
0.0%
99.6%
timer
keyboard
cascade [4]
rtc
acpi
Free
-2
0
Shared
0
Buffers
0
Cached
0
Load average: 0.00 0.00 0.00 1/106 31902
page in :
page out:
swap in :
swap out:
context :
irq
irq
irq
irq
irq
0
0
0
0
1087
10:
11:
12:
14:
15:
disk
disk
disk
disk
0
32
132
0
0
1:
2:
3:
4:
0r
0r
0r
0r
usb-uhci, usb-uhci
ehci_hcd, usb-uhci,
PS/2 Mouse
ide0
ide1
PCI Resources: lspci
The command lspci lists the PCI resources:
$ lspci
00:00.0 Host bridge: VIA Technologies, Inc. \
VT8366/A/7 [Apollo KT266/A/333]
00:01.0 PCI bridge: VIA Technologies, Inc. \
VT8366/A/7 [Apollo KT266/A/333 AGP]
00:0b.0 Ethernet controller: Digital Equipment Corporation \
DECchip 21140 [FasterNet] (rev 22)
00:10.0 USB Controller: VIA Technologies, Inc. USB (rev 80)
00:10.1 USB Controller: VIA Technologies, Inc. USB (rev 80)
00:10.2 USB Controller: VIA Technologies, Inc. USB (rev 80)
00:10.3 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 82)
00:11.0 ISA bridge: VIA Technologies, Inc. VT8235 ISA Bridge
366
0w
0w
0w
0w
00:11.1 IDE interface: VIA Technologies, Inc. VT82C586/B/686A/B \
PIPC Bus Master IDE (rev 06)
00:11.5 Multimedia audio controller: VIA Technologies, Inc. \
VT8233 AC97 Audio Controller (rev 50)
01:00.0 VGA compatible controller: Matrox Graphics, Inc. \
MGA G550 AGP (rev 01)
Using -v results in a more detailed listing:
$ lspci -v
[...]
01:00.0 \
VGA compatible controller: Matrox Graphics, Inc. MGA G550 AGP (rev 01) \
(prog-if 00 [VGA])
Subsystem: Matrox Graphics, Inc. Millennium G550 Dual Head DDR 32Mb
Flags: bus master, medium devsel, latency 32, IRQ 10
Memory at d8000000 (32-bit, prefetchable) [size=32M]
Memory at da000000 (32-bit, non-prefetchable) [size=16K]
Memory at db000000 (32-bit, non-prefetchable) [size=8M]
Expansion ROM at <unassigned> [disabled] [size=128K]
Capabilities: <available only to root>
Information about device name resolution is obtained from file /usr/share/pci
.ids. PCI IDs not listed in this file are marked “Unknown device”.
The parameter -vv produces all the information that could be queried by the program.
To view the pure numeric values, you should use the parameter -n.
25.17
System Calls of a Program
Run: strace
The utility strace enables you to trace all the system calls of a process currently
running. Enter the command in the normal way, adding strace at the beginning of
the line:
$ strace ls
execve("/bin/ls", ["ls"], [/* 88 vars */]) = 0
uname({sys="Linux", node="edison", ...}) = 0
brk(0)
= 0x805b000
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) \
= 0x40017000
open("/etc/ld.so.preload", O_RDONLY)
= -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)
= 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=76333, ...}) = 0
old_mmap(NULL, 76333, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40018000
[...]
System Monitoring Utilities
367
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(1, TIOCGWINSZ, {ws_row=53, ws_col=110, ws_xpixel=897, ws_ypixel=693}) = 0
open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=144, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)
= 0
getdents64(3, /* 5 entries */, 4096)
= 160
getdents64(3, /* 0 entries */, 4096)
= 0
close(3)
= 0
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 48), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) \
= 0x40018000
write(1, "ltrace-ls.txt myfile.txt strac"..., 41) = 41
munmap(0x40018000, 4096)
= 0
exit_group(0)
= ?
For example, to trace all attempts to open a particular file, use the following:
$ strace -e open ls myfile.txt
open("/etc/ld.so.preload", O_RDONLY)
= -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)
= 3
open("/lib/tls/librt.so.1", O_RDONLY)
= 3
open("/lib/libacl.so.1", O_RDONLY)
= 3
open("/lib/libselinux.so.1", O_RDONLY) = 3
open("/lib/tls/libc.so.6", O_RDONLY)
= 3
open("/lib/tls/libpthread.so.0", O_RDONLY) = 3
open("/lib/libattr.so.1", O_RDONLY)
= 3
open("/proc/mounts", O_RDONLY)
= 3
[...]
open("/proc/filesystems", O_RDONLY)
= 3
open("/proc/self/attr/current", O_RDONLY) = 4
To trace all the child processes, use the parameter -f. The behavior and output format
of strace can be largely controlled. For information, see man strace.
25.18
Library Calls of a Program
Run: ltrace
The command ltrace enables you to trace the library calls of a process. This command
is used in a similar fashion to strace. The parameter -c outputs the number and duration of the library calls that have occurred:
$ ltrace -c find /usr/share/doc
% time
seconds usecs/call
calls
errors syscall
------ ----------- ----------- --------- --------- ---------------86.27
1.071814
30
35327
write
10.15
0.126092
38
3297
getdents64
2.33
0.028931
3
10208
lstat64
368
0.55
0.006861
2
3122
1 chdir
0.39
0.004890
3
1567
2 open
[...]
0.00
0.000003
3
1
uname
0.00
0.000001
1
1
time
------ ----------- ----------- --------- --------- ---------------100.00
1.242403
58269
3 total
25.19
Specifying the Required
Library: ldd
The command ldd can be used to find out which libraries would load the dynamic
executable specified as argument:
$ ldd /bin/ls
linux-gate.so.1 => (0xffffe000)
librt.so.1 => /lib/tls/librt.so.1 (0x4002b000)
libacl.so.1 => /lib/libacl.so.1 (0x40033000)
libselinux.so.1 => /lib/libselinux.so.1 (0x40039000)
libc.so.6 => /lib/tls/libc.so.6 (0x40048000)
libpthread.so.0 => /lib/tls/libpthread.so.0 (0x4015d000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
libattr.so.1 => /lib/libattr.so.1 (0x4016d000)
Static binaries do not need any dynamic libraries:
$ ldd /bin/sash
not a dynamic executable
$ file /bin/sash
/bin/sash: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), \
for GNU/Linux 2.2.5, statically linked, stripped
25.20
Additional Information about
ELF Binaries
The content of binaries can be read with the readelf utility. This even works with
ELF files that were built for other hardware architectures:
$ readelf --file-header /bin/ls
ELF Header:
Magic:
7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class:
ELF32
Data:
2's complement, little endian
System Monitoring Utilities
369
Version:
OS/ABI:
ABI Version:
Type:
Machine:
Version:
Entry point address:
Start of program headers:
Start of section headers:
Flags:
Size of this header:
Size of program headers:
Number of program headers:
Size of section headers:
Number of section headers:
Section header string table index:
25.21
1 (current)
UNIX - System V
0
EXEC (Executable file)
Intel 80386
0x1
0x8049b40
52 (bytes into file)
76192 (bytes into file)
0x0
52 (bytes)
32 (bytes)
9
40 (bytes)
29
26
Interprocess Communication:
ipcs
The command ipcs produces a list of the IPC resources currently in use:
$ ipcs
------ Shared Memory Segments -------key
shmid
owner
perms
0x000027d9 5734403
toms
660
0x00000000 5767172
toms
666
0x00000000 5799941
toms
666
bytes
64528
37044
37044
------ Semaphore Arrays -------key
semid
owner
perms
0x000027d9 0
toms
660
1
------ Message Queues -------key
msqid
owner
25.22
perms
nattch
status
2
2
2
nsems
used-bytes
messages
Time Measurement with time
The time spent by commands can be determined with the time utility. This utility is
available in two versions: as a shell built-in and as a program (/usr/bin/time).
$ time find . > /dev/null
real
user
sys
370
0m4.051s
0m0.042s
0m0.205s
Part VIII System
32-Bit and 64-Bit Applications in a
64-Bit System Environment
26
SUSE Linux is available for several 64-bit platforms. This does not necessarily mean
that all the applications included have already been ported to 64-bit platforms. SUSE
Linux supports the use of 32-bit applications in a 64-bit system environment. This
chapter offers a brief overview of how this support is implemented on 64-bit SUSE
Linux platforms. It explains how 32-bit applications are executed (runtime support)
and how 32-bit applications should be compiled to enable them to run both in 32-bit
and 64-bit system environments. Additionally, find information about the Kernel API
and an explanation of how 32-bit applications can run under a 64-bit kernel.
SUSE Linux for the 64-bit platforms AMD64 and EM64T is designed so that existing
32-bit applications run in the 64-bit environment “out-of-the-box.” This support means
that you can continue to use your preferred 32-bit applications without waiting for a
corresponding 64-bit port to become available.
26.1
Runtime Support
IMPORTANT: Conflicts between Application Versions
If an application is available both for 32-bit and 64-bit environments, the parallel installation of both versions is bound to lead to problems. In such cases,
decide on one of the two versions and install and use this.
To be executed correctly, every application requires a range of libraries. Unfortunately,
the names for the 32-bit and 64-bit versions of these libraries are identical. They must
be differentiated from each other in another way.
32-Bit and 64-Bit Applications in a 64-Bit System Environment
373
To retain compatibility with the 32-bit version, the libraries are stored at the same place
in the system as in the 32-bit environment. The 32-bit version of libc.so.6 is located
under /lib/libc.so.6 in both the 32-bit and 64-bit environments.
All 64-bit libraries and object files are located in directories called lib64. The 64-bit
object files you would normally expect to find under /lib, /usr/lib, and /usr/
X11R6/lib are now found under /lib64, /usr/lib64, and /usr/X11R6/
lib64. This means that there is space for the 32-bit libraries under /lib, /usr/lib
and /usr/X11R6/lib, so the filename for both versions can remain unchanged.
No subdirectories of the object directories whose data content does not depend on the
word size are moved. For example, the X11 fonts are still found in the usual location
under /usr/X11R6/lib/X11/fonts. This scheme conforms to the LSB (Linux
Standards Base) and the FHS (File System Hierarchy Standard).
26.2
Software Development
A biarch development toolchain allows generatation of 32-bit and 64-bit objects. The
default is to compile 64-bit objects. It is possible to generate 32-bit objects by using
special flags. For GCC, this special flag is -m32.
All header files must be written in an architecture-independent form. The installed 32bit and 64-bit libraries must have an API (application programming interface) that
matches the installed header files. The normal SUSE environment is designed according
to this principle. In the case of manually updated libraries, resolve these issues yourself.
26.3
Software Compilation on Biarch
Platforms
To develop binaries for the other architecture on a biarch architecture, the respective
libraries for the second architecture must additionally be installed. These packages are
called rpmname-32bit . You also need the respective headers and libraries from the
rpmname-devel packages and the development libraries for the second architecture
from rpmname-devel-32bit.
374
Most Open Source programs use an autoconf-based program configuration. To use
autoconf for configuring a program for the second architecture, overwrite the normal
compiler and linker settings of autoconf by running the configure script with
additional environment variables.
The following example refers to an AMD64 or EM64T system with x86 as the second
architecture:
1.
Set autoconf to use the 32-bit compiler:
CC="gcc -m32"
2.
Instruct the linker to process 32-bit objects:
LD="ld -m elf64_i386"
3.
Set the assembler to generate 32-bit objects:
AS="gcc -c -m32"
4.
Determine that the libraries for libtool and so on come from /usr/lib:
LDFLAGS="-L/usr/lib"
5.
Determine that the libraries are stored in the lib subdirectory:
--libdir=/usr/lib
6.
Determine that the 32-bit X libraries are used:
--x-libraries=/usr/X11R6/lib/
Not all of these variables are needed for every program. Adapt them to the respective
program.
CC="gcc -m64"
\
LDFLAGS="-L/usr/lib64;" \
.configure
\
--prefix=/usr \
--libdir=/usr/lib64
make
make install
32-Bit and 64-Bit Applications in a 64-Bit System Environment
375
26.4
Kernel Specifications
The 64-bit kernels for AMD64 and EM64T offer both a 64-bit and a 32-bit kernel ABI
(application binary interface). The latter is identical with the ABI for the corresponding
32-bit kernel. This means that the 32-bit application can communicate with the 64-bit
kernel in the same way as with the 32-bit kernel.
The 32-bit emulation of system calls for a 64-bit kernel does not support a number of
APIs used by system programs. This depends on the platform. For this reason, a small
number of applications, like lspci or the LVM administration programs, must be
compiled as 64-bit programs to function properly.
A 64-bit kernel can only load 64-bit kernel modules that have been specially compiled
for this kernel. It is not possible to use 32-bit kernel modules.
TIP
Some applications require separate kernel-loadable modules. If you intend to
use such a 32-bit application in a 64-bit system environment, contact the
provider of this application and SUSE to make sure that the 64-bit version of
the kernel-loadable module and the 32-bit compiled version of the kernel API
are available for this module.
376
27
Working with the Shell
Graphical user interfaces are becoming increasingly important for Linux, but using the
mouse is not always the best way to perform daily tasks. The command line provides
high flexibility and efficiency. Text-based applications are especially important for
controlling computers over slow network links or if you want to perform tasks as root
on the command line in an xterm. The Bash shell is the default command line interpreter
on SUSE Linux.
Linux is a multiuser system and access to files is controlled by user permissions. Whether
using the command line or a GUI, it is useful to understand the permission concept.
When using the command line, a number of commands are important. The vi text editor
is often used when configuring a system from the command line. It is also popular with
many system administrators and developers.
27.1
Using of Bash on the Command
Line
In the KDE taskbar, there is an icon depicting a monitor with a seashell. When you
click this icon, a terminal window opens in which to enter commands. Konsole, the
terminal program, normally runs Bash (Bourne again shell), a program developed as
part of the GNU project. On the GNOME desktop, click an icon with a computer
monitor in the upper panel to start a terminal that normally runs Bash.
Working with the Shell
377
Once you have opened the shell, see the prompt on the first line. The prompt usually
consists of the username, hostname, and current path, but it can be customized. When
the cursor is after this prompt, you can send commands directly to your computer system.
27.1.1 Entering Commands
A command consists of several elements. The first element is always the actual command, followed by parameters or options. Commands are executed when you press
Enter . Before doing so, easily edit the command line, add options, or correct typing errors. One of the most frequently used commands is ls, which can be used with or
without arguments. Entering the plain ls command shows the contents of the current
directory.
Options are prefixed with a hyphen. The command ls -l, for example, shows the
contents of the same directory in full detail (long listing format). Next to each filename,
see the date when the file was created, the file size in bytes, and further details, which
are covered later. One important option that exists for many commands is --help.
By entering ls --help, display all the options for the ls command.
It is important to get the “quoting” right. If a filename contains a space, either escape
the space using a back slash (\) or enclose the filename in single or double quotes.
Otherwise Bash interprets a filename like My Documents as the names of two files
or directories. The difference between single and double quotes is that variable expansion
takes place within double quotes. Single quotes ensure that the shell sees the quoted
string literally.
27.1.2 Files and Directories
To use the shell efficiently, it is really useful to have some knowledge of the file and
directory structures of a Linux system. You can think of directories as electronic folders
in which files, programs, and subdirectories are stored. The top level directory in the
hierarchy is the root directory, referred to as /. This is the place from which all other
directories can be accessed.
The /home directory contains the directories in which the individual users can store
their personal files. Figure 27.1, “Excerpt from a Standard Directory Tree” (page 379)
shows the standard directory tree in Linux, with the home directories of the example
users xyz, linux, and tux. The directory tree of a Linux system has a functional
378
structure that follows the Filesystem Hierarchy Standard (FHS). The following list
provides a brief description of the standard directories in Linux.
Figure 27.1
Excerpt from a Standard Directory Tree
/
bin
boot
dev
etc
home
lib
mnt
media
vmlinuz
kde
opt
proc
root
srv
sbin
sys
tmp
usr
var
gnome
ld.so
hda
sda
st0
yxz
bin
linux
tux
bin
X11R6
test.c
Mail
bin
xdm
xterm
etc
lib
local
sbin
share
f2c
lib
man
xv
bin
bin
lib
lib
ftp
pub
man
faq
doc
howto
man
packages
/
Root directory, starting point of the directory tree
/home
Personal directories of users
/dev
Device files that represent hardware components
/etc
Important files for system configuration
/etc/init.d
Boot scripts
/usr/bin
Generally accessible programs
/bin
Programs needed early in the boot process
Working with the Shell
379
/usr/sbin
Programs reserved for the system administrator
/sbin
Programs reserved for the system administrator and needed for booting
/usr/include
Header files for the C compiler
/usr/include/g++
Header files for the C++ compiler
/usr/share/doc
Various documentation files
/usr/share/man
System manual pages (man pages)
/usr/src
Source code of system software
/usr/src/linux
Kernel source code
/tmp, /var/tmp
Temporary files
/usr
All application programs
/var
Configuration files (such as those linked from /usr)
/var/log
System log files
/var/adm
System administration data
/lib
Shared libraries (for dynamically linked programs)
380
/proc
Process file system
/sys
System file system where all device information for the kernel is gathered
/usr/local
Local, distribution-independent extensions
/opt
Optional software, larger add-on program packages (such as KDE, GNOME,
Netscape)
27.1.3 Bash Features
There are two important features of the shell that can make your work a lot easier:
History
To repeat a command that has been entered before, press ↑ until the previous
command appears at the prompt. Move forward through the list of previously entered
commands by pressing ↓ . To edit the command line, just move the cursor to the
desired position using the arrow keys and start typing. Use Ctrl + R to search in
the history.
Completion
Complete a filename to its full length after typing its first letters until it can be
uniquely identified. To do so, type the first letters then hit Tab . If there are several
filenames starting with the same letters, obtain a list of them by hitting Tab twice.
First Example: Managing Files
Now that you know what a command looks like, which directories exist in SUSE Linux,
and how to speed up things when using Bash, put this knowledge into practice with a
small exercise.
1.
Open a console from the KDE or GNOME desktop by clicking the shell icon.
2.
Enter the ls command to see the contents of your home directory.
Working with the Shell
381
3.
Use the command mkdir (which stands for make directory) to create a new
subdirectory called test by entering mkdir test.
4.
Now launch an editor by pressing Alt + F2 and entering kate Kate in for KDE
gedit for Gedit in GNOME. Type a few letters in the editor then save the file
as Testfile in your home directory. Linux distinguishes between uppercase
and lowercase. For this example, use an uppercase T.
5.
View the contents of your home directory again. Instead of typing ls again, just
press ↑ twice and the ls command should reappear at the prompt. To execute
the command, hit Enter . The newly created directory test should appear in
blue letters and Testfile in black. This is how directories and files can be
distinguished in a console.
6.
Move Testfile into the subdirectory test with the command mv. To speed
this up, use the expansion function: just enter mv T and press Tab . As long as
there is no other file beginning with this letter in the directory, the shell expands
the filename and adds the string estfile. Otherwise, add a letter or two yourself
and test Tab each time to see whether the shell can now expand the name. Finally,
type a space then test after the expanded filename and press Enter to execute
the command.
7.
At this point, Testfile should no longer be in the directory. Check this by
entering ls again.
8.
To see whether the file has been successfully moved, change into the directory
test with the command cd test. Now enter ls again. You should see
Testfile in the listing. Change back to your home directory at any point by
entering only cd.
9.
To make a copy of a file, use cp. For instance, enter cp Testfile
Testbackup to copy Testfile to Testbackup. Once again, the command
ls can be used to see whether both files are in the directory.
27.1.4 Specifying Paths
When working with files or directories, it is important specify the correct path. However,
you do not need to enter the entire (absolute) path from the root directory to the respective file. You can start from the current directory. Address your home directory directly
382
with ~. This means that there are two ways to list the file Testfile in the directory
test: by entering the relative path with ls test or by specifying the absolute path
with ls ~/test.
To list the contents of home directories of other users, enter ls ~username. In the
example directory tree, one of the sample users is tux. In this case, ls ~tux would
list the contents of the home directory of tux.
Refer to the current directory with a dot (.). The next higher level in the tree is represented by two dots (..). By entering ls .., see the contents of the parent directory
of the current directory. The command ls ../.. shows the contents of the directory
two levels higher in the hierarchy.
Second Example: Working with Paths
Here is another example to illustrate how to move around in the directories of your
SUSE Linux system.
1.
Change into your home directory with the command cd. Then create a directory
in it with the name test2 by entering mkdir test2.
2.
Change into the new directory with cd test2 and create a subdirectory in it
with the name subdirectory. To change into it, use the expansion function:
enter cd su then press Tab . The shell expands the rest of the directory name.
3.
Now try to move the previously created file Testbackup into the current directory (subdirectory) without changing the directory again. To achieve
this, specify the relative path to that file: mv ../../test/Testbackup
. (note the dot at the end). The dot at the end of this command is required to tell
the shell that the current directory is the destination to which to move the file.
../../, in this example, refers to your home directory.
27.1.5 Wild Cards
Another convenience offered by the shell is wild cards for pathname expansion. There
are three different types of these in Bash:
?
Matches exactly one arbitrary character
Working with the Shell
383
*
Matches any number of characters
[set]
Matches one of the characters from the group specified inside the square brackets,
which is represented here by the string set. As part of set you can also specify
character classes using the syntax [:class:], where a class is one of alnum,
alpha, ascii, etc.
Using ! or ^ at the beginning of the group ([!set]) matches one character other than
those identified by set.
Assuming that your test directory contains the files Testfile, Testfile1,
Testfile2, and datafile, the command ls Testfile? lists the files
Testfile1 and Testfile2. With ls Test*, the list also includes Testfile.
ls *fil* shows all the sample files. Finally, you can use the set wild card to address
all sample files whose last character is a number: ls Testfile[1-9] or, using
classes, ls Testfile[[:digit:]].
Of the four types of wild cards, the most inclusive one is the asterisk. It could be used
to copy all files contained in one directory to another one or to delete all files with one
command. The command rm *fil*, for instance, would delete all files in the current
directory whose name includes the string fil.
27.1.6 Less and More
Linux includes two small programs for viewing text files directly in the shell. Rather
than starting an editor to read a file like Readme.txt, simply enter less
Readme.txt to display the text in the console window. Use Space to scroll down one
page. Use Page Up and Page Down to move forward or backward in the text. To exit less,
press Q .
Instead of less, you can also use the older program more. However, it is less convenient
because it does not allow you to scroll backwards.
The program less got its name from the the precept that less is more and can also be
used to view the output of commands in a convenient way. To see how this works, read
Section 27.1.7, “Pipes and Redirection” (page 385).
384
27.1.7 Pipes and Redirection
Normally, the standard output in the shell is your screen or the console window and
the standard input is the keyboard. To forward the output of a command to an application
like less, use a pipeline.
To view the files in the test directory, enter the command ls test | less. The
contents of the test directory are then displayed with less. This only makes sense if
the normal output with ls would be too lengthy. For instance, if you view the contents
of the dev directory with ls /dev, you only see a small portion in the window. View
the entire list with ls /dev | less.
It is also possible to save the output of commands to a file. For example, echo "test
one" > Content generates a new file called Content that contains the words
test one. View the file with less Content.
You can also use a file as the input for a command. For example, with tr replace
characters from standard input that redirected from the file Content and write the
result to standard output: replace t with x by calling tr t x < Content. The
output of tr is sent to the screen.
If you need a new file containing the output, pipe the output of tr to a file. To test this,
change into test and enter the command tr t x < ../Content > new. Finally,
view new with less new.
Just like the standard output, the standard error output is sent to the console. However,
to redirect the standard error output to a file named errors, append 2> errors to
the corresponding command. Both standard output and standard error are saved to one
file named alloutput if you append >& alloutput. Finally, to append the output
of a command to an already existing file, the command must be followed by >> instead
of >.
27.1.8 Archives and Data Compression
Now that you have already created a number of files and directories, consider the subject
of archives and data compression. Suppose you want to have the entire test directory
packed in one file that you can save on a USB stick as a backup copy or send by e-mail.
Working with the Shell
385
To do so, use the command tar (for tape archiver). With tar --help, view all the
options for the tar command. The most important of these options are explained here:
-c
(for create) Create a new archive.
-t
(for table) Display the contents of an archive.
-x
(for extract) Unpack the archive.
-v
(for verbose) Show all files on screen while creating the archive.
-f
(for file) Choose a filename for the archive file. When creating an archive, this option
must always be given as the last one.
To pack the test directory with all its files and subdirectories into an archive named
testarchive.tar, use the options -c and -f. For testing purposes, also add -v
to follow the progress of the archiving, although this option is not mandatory. After
using cd to change to your home directory where the test directory is located, enter
tar -cvf testarchive.tar test. After that, view the contents of the archive
file with tar -tf testarchive.tar. The test directory with all its files and
directories has remained unchanged on your hard disk. To unpack the archive, enter
tar -xvf testarchive.tar, but do not try this yet.
For file compression, the obvious choice is gzip or, for a even better compression ratio,
bzip2. Just enter gzip testarchive.tar (or bzip2 testarchive.tar,
but gzip is used in this example). With ls, now see that the file testarchive.tar
is no longer there and that the file testarchive.tar.gz has been created instead.
This file is much smaller and therefore much better suited for transfer via e-mail or
storage on a USB stick.
Now, unpack this file in the test2 directory created earlier. To do so, enter cp
testarchive.tar.gz test2 to copy the file to that directory. Change to the
directory with cd test2. A compressed archive with the .tar.gz extension can
be unzipped with the gunzip command. Enter gunzip testarchive.tar.gz,
which results in the file testarchive.tar, which then needs to be extracted or
386
untarred with tar -xvf testarchive.tar. You can also unzip and extract a
compressed archive in one step with tar -xvf testarchive.tar.gz (adding
the -z option is no longer required). With ls, you can see that a new test directory
has been created with the same contents as your test directory in your home directory.
27.1.9 mtools
mtools are a set of commands for working with MS-DOS file systems. The commands
included in mtools allow you to address the first floppy drive as a:, just like under
MS-DOS, and the commands are like MS-DOS commands except they are prefixed
with an m.
mdir a:
Displays the contents of the floppy disk in drive a:
mcopy Testfile a:
Copies the file Testfile to the floppy disk
mdel a:Testfile
Deletes Testfile in a:
mformat a:
Formats the floppy disk in MS-DOS format (using the fdformat command)
mcd a:
Makes a: your current directory
mmd a:test
Creates the subdirectory test on the floppy disk
mrd a:test
Deletes the subdirectory test from the floppy disk
27.1.10
Cleaning Up
After this crash course, you should be familiar with the basics of the Linux shell or
command line. You may want to clean up your home directory by deleting the various
test files and directories using the rm and rmdir commands. In Section 27.3, “Important
Working with the Shell
387
Linux Commands” (page 393), find a list of the most important commands and a brief
description of their functions.
27.2
Users and Access Permissions
Since its inception in the early 1990s, Linux has been developed as a multiuser system.
Any number of users can work on it simultaneously. Users need to log in to the system
before starting a session at their workstations. Each user has a username with a corresponding password. This differentiation of users guarantees that unauthorized users
cannot see files for which they do not have permission. Larger changes to the system,
such as installing new programs, are also usually impossible or restricted for normal
users. Only the root user, or super user, has the unrestricted capacity to make changes
to the system and has unlimited access to all files. Those who use this concept wisely,
only logging in with full root access when necessary, can cut back the risk of unintentional loss of data. Because under normal circumstances only root can delete system
files or format hard disks, the threat from the Trojan horse effect or from accidentally
entering destructive commands can be significantly reduced.
27.2.1 File System Permissions
Basically, every file in a Linux file system belongs to a user and a group. Both of these
proprietary groups and all others can be authorized to write, read, or execute these files.
A group, in this case, can be defined as a set of connected users with certain collective
rights. For example, call a group working on a certain project project3. Every user
in a Linux system is a member of at least one proprietary group, normally users.
There can be as many groups in a system as needed, but only root is able to add
groups. Every user can find out, with the command groups, of which groups he is a
member.
File Access
The organization of permissions in the file system differs for files and directories.
File permission information can be displayed with the command ls -l. The output
could appear as in Example 27.1, “Sample Output Showing File Permissions”
(page 389).
388
Example 27.1
Sample Output Showing File Permissions
-rw-r----- 1 tux project3 14197 Jun 21
15:03 Roadmap
As shown in the third column, this file belongs to user tux. It is assigned to the
group project3. To discover the user permissions of the Roadmap file, the first
column must be examined more closely.
-
rw-
r--
---
Type
Users Permissions
Group Permissions
Permissions for Other
Users
This column consists of one leading character followed by nine characters grouped
in threes. The first of the ten letters stands for the type of file system component.
The hyphen (–) shows that this is a file. A directory (d), a link (l), a block device
(b), or a character device could also be indicated.
The next three blocks follow a standard pattern. The first three characters refer to
whether the file is readable (r) or not (–). A w in the middle portion symbolizes
that the corresponding object can be edited and a hyphen (–) means it is not possible
to write to the file. An x in the third position denotes that the object can be executed.
Because the file in this example is a text file and not one that is executable, executable access for this particular file is not needed.
In this example, tux has, as owner of the file Roadmap, read (r) and write access
(w) to it, but cannot execute it (x). The members of the group project3 can read
the file, but they cannot modify it or execute it. Other users do not have any access
to this file. Other permissions can be assigned by means of ACLs (access control
lists). See Section 27.2.6, “Access Control Lists” (page 392) for background information.
Directory Permissions
Access permissions for directories have the type d. For directories, the individual
permissions have a slightly different meaning.
Example 27.2
Sample Output Showing Directory Permissions
drwxrwxr-x 1 tux project3 35 Jun 21 15:15
ProjectData
Working with the Shell
389
In Example 27.2, “Sample Output Showing Directory Permissions” (page 389), the
owner (tux) and the owning group (project3) of the directory ProjectData
are easy to recognize. In contrast to the file access permissions from File Access
(page 388), the set reading permission (r) means that the contents of the directory
can be shown. The write permission (w) means that new files can be created. The
executable permission (x) means that the user can change to this directory. In the
above example, the user tux as well as the members of the group project3 can
change to the ProjectData directory (x), view the contents (r), and add or delete
files (w). The rest of the users, on the other hand, are given less access. They may
enter the directory (x) and browse through it (r), but not insert any new files (w).
27.2.2 Modifying File Permissions
Changing Access Permissions
The access permissions of a file or directory can be changed by the owner and, of
course, by root with the command chmod followed by the parameters changing
the permissions and one or more filenames. The parameters form different categories:
1.
users concerned
• u (user)—owner of the file
• g (group)—group that owns the file
• o (others)—additional users (if no parameter is given, the changes apply to all
categories)
2.
a character for deletion (–), setting (=), or insertion (+)
3.
the abbreviations
• r—read
• w—write
• x—execute
4.
390
filename or filenames separated by spaces
If, for example, the user tux in Example 27.2, “Sample Output Showing Directory
Permissions” (page 389) also wants to grant other users write (w) access to the directory ProjectData, he can do this using the command chmod o+w
ProjectData.
If, however, he wants to deny all users other than himself write permissions, he can
do this by entering the command chmod go-w ProjectData. To prohibit all
users from adding a new file to the folder ProjectData, enter chmod -w
ProjectData. Now, not even the owner can write to the file without first
reestablishing write permissions.
Changing Ownership Permissions
Other important commands to control the ownership and permissions of the file
system components are chown (change owner) and chgrp (change group). The
command chown can be used to transfer ownership of a file to another user. However, only root is permitted to perform this change.
Suppose the file Roadmap from Example 27.2, “Sample Output Showing Directory
Permissions” (page 389) should no longer belong to tux, but to the user geeko.
root should then enter chown geeko Roadmap.
chgrp changes the group ownership of the file. However, the owner of the file
must be a member of the new group. In this way, the user tux from Example 27.1,
“Sample Output Showing File Permissions” (page 389) can switch the group owning
the file ProjectData to project4 with the command chgrp project4
ProjectData, as long as he is a member of this new group.
27.2.3 The setuid Bit
In certain situations, the access permissions may be too restrictive. Therefore, Linux
has additional settings that enable the temporary change of the current user and group
identity for a specific action. For example, the passwd program normally requires
root permissions to access /etc/passwd. This file contains some important information, like the home directories of users and user and group IDs. Thus, a normal user
would not be able to change passwd, because it would be too dangerous to grant all
users direct access to this file. A possible solution to this problem is the setuid mechanism. setuid (set user ID) is a special file attribute that instructs the system to execute
programs marked accordingly under a specific user ID. Consider the passwd command:
Working with the Shell
391
-rwsr-xr-x
1 root shadow 80036 2004-10-02 11:08 /usr/bin/passwd
You can see the s that denotes that the setuid bit is set for the user permission. By
means of the setuid bit, all users starting the passwd command execute it as root.
27.2.4 The setgid Bit
The setuid bit applies to users. However, there is also an equivalent property for groups:
the setgid bit. A program for which this bit was set runs under the group ID under which
it was saved, no matter which user starts it. Therefore, in a directory with the setgid bit,
all newly created files and subdirectories are assigned to the group to which the directory belongs. Consider the following example directory:
drwxrws--- 2 tux archive 48 Nov 19 17:12
backup
You can see the s that denotes that the setgid bit is set for the group permission. The
owner of the directory and members of the group archive may access this directory.
Users that are not members of this group are “mapped” to the respective group. The
effective group ID of all written files will be archive. For example, a backup program
that runs with the group ID archive is able to access this directory even without root
privileges.
27.2.5 The Sticky Bit
There is also the sticky bit. It makes a difference whether it belongs to an executable
program or a directory. If it belongs to a program, a file marked in this way is loaded
to RAM to avoid needing to get it from the hard disk each time it is used. This attribute
is used rarely, because modern hard disks are fast enough. If this bit is assigned to a
directory, it prevents users from deleting each other's files. Typical examples include
the /tmp and /var/tmp directories:
drwxrwxrwt
2 root
root
1160 2002-11-19 17:15 /tmp
27.2.6 Access Control Lists
The traditional permission concept for Linux file system objects, such as files or directories, can be expanded by means of ACLs (access control lists). They allow the assignment of permissions to individual users or groups other than the original owner or
owning group of a file system object.
392
Files or directories bearing extended access permissions can be detected with a simple
ls -l command:
-rw-r--r--+ 1 tux project3 14197 Jun 21
15:03 Roadmap
Roadmap is owned by tux who belongs to the group project3. tux holds both
write and read access to this file. The group as well as all other users have read access.
The only difference that distinguishes this file from a file without an ACL is the additional + in the column holding the permission bits.
Get details about the ACL by executing getfacl Roadmap:
# file: Roadmap
# owner: tux
# group: project3
user::rwuser:jane:rwgroup::r-group:djungle:rwmask::r-other::---
effective: r-effective: r--
The first three lines of the output do not hold any information not available with ls
-l. These lines only state filename, owner, and owning group. Lines 4 to 9 hold the
ACL entries. Conventional access permissions represent a subset of those possible when
using ACLs. The example ACL grants read and write access to the owner of the file as
well as to user jane (lines 4 and 5). The conventional concept has been expanded allowing access to an extra user. The same applies to the handling of group access. The
owning group holds read permissions (line 6) and the group djungle holds read and
write permissions. The mask entry in line 8 reduces the effective permissions for the
user jane and the group djungle to read access. Other users and groups do not get
any kind of access to the file (line 9).
Only very basic information has been provided here. Find more detailed information
about ACLs in Chapter 24, Access Control Lists in Linux (page 341).
27.3
Important Linux Commands
This section gives insight into the most important commands of your SUSE Linux
system. There are many more commands than listed in this chapter. Along with the individual commands, parameters are listed and, where appropriate, a typical sample application is introduced. To learn more about the various commands, use the manual
Working with the Shell
393
pages, accessed with man followed by the name of the command, for example, man
ls.
In the man pages, move up and down with PgUp and PgDn . Move between the beginning
and the end of a document with Home and End . End this viewing mode by pressing Q .
Learn more about the man command itself with man man.
In the following overview, the individual command elements are written in different
typefaces. The actual command and its mandatory options are always printed as
command option. Specifications or parameters that are not required are placed in
[square brackets].
Adjust the settings to your needs. It makes no sense to write ls file, if no file named
file actually exists. You can usually combine several parameters, for example, by
writing ls -la instead of ls -l -a.
27.3.1 File Commands
The following section lists the most important commands for file management. It covers
anything from general file administration to manipulation of file system ACLs.
File Administration
ls [options] [files]
If you run ls without any additional parameters, the program lists the contents of
the current directory in short form.
-l
Detailed list
-a
Displays hidden files
cp [options] source target
Copies source to target.
394
-i
Waits for confirmation, if necessary, before an existing target is overwritten
-r
Copies recursively (includes subdirectories)
mv [options] source target
Copies source to target then deletes the original source.
-b
Creates a backup copy of the source before moving
-i
Waits for confirmation, if necessary, before an existing targetfile is overwritten
rm [options] files
Removes the specified files from the file system. Directories are not removed by
rm unless the option -r is used.
-r
Deletes any existing subdirectories
-i
Waits for confirmation before deleting each file.
ln [options] source target
Creates an internal link from source to target. Normally, such a link points
directly to source on the same file system. However, if ln is executed with the
-s option, it creates a symbolic link that only points to the directory in which
source is located, enabling linking across file systems.
-s
Creates a symbolic link
Working with the Shell
395
cd [options] [directory]
Changes the current directory. cd without any parameters changes to the user's
home directory.
mkdir [options] directory
Creates a new directory.
rmdir [options] directory
Deletes the specified directory, if it is already empty.
chown [options] username[:[group]] files
Transfers ownership of a file to the user with the specified username.
-R
Changes files and directories in all subdirectories
chgrp [options] groupname files
Transfers the group ownership of a given file to the group with the specified
group name. The file owner can only change group ownership if a member of both
the current and the new group.
chmod [options] mode files
Changes the access permissions.
The mode parameter has three parts: group, access, and access type.
group accepts the following characters:
u
user
g
group
o
others
396
For access, grant access with + and deny it with -.
The access type is controlled by the following options:
r
read
w
write
x
execute—executing files or changing to the directory
s
Setuid bit—the application or program is started as if it were started by the
owner of the file
As an alternative, a numeric code can be used. The four digits of this code are
composed of the sum of the values 4, 2, and 1—the decimal result of a binary mask.
The first digit sets the set user ID (SUID) (4), the set group ID (2), and the sticky
(1) bits. The second digit defines the permissions of the owner of the file. The third
digit defines the permissions of the group members and the last digit sets the permissions for all other users. The read permission is set with 4, the write permission with
2, and the permission for executing a file is set with 1. The owner of a file would
usually receive a 6 or a 7 for executable files.
gzip [parameters] files
This program compresses the contents of files using complex mathematical algorithms. Files compressed in this way are given the extension .gz and need to be
uncompressed before they can be used. To compress several files or even entire directories, use the tar command.
-d
Decompresses the packed gzip files so they return to their original size and can
be processed normally (like the command gunzip)
Working with the Shell
397
tar options archive files
tar puts one or more files into an archive. Compression is optional. tar is a quite
complex command with a number of options available. The most frequently used
options are:
-f
Writes the output to a file and not to the screen as is usually the case
-c
Creates a new tar archive
-r
Adds files to an existing archive
-t
Outputs the contents of an archive
-u
Adds files, but only if they are newer than the files already contained in the
archive
-x
Unpacks files from an archive (extraction)
-z
Packs the resulting archive with gzip
-j
Compresses the resulting archive with bzip2
-v
Lists files processed
The archive files created by tar end with .tar. If the tar archive was also compressed using gzip, the ending is .tgz or .tar.gz. If it was compressed using
bzip2, the ending is .tar.bz2. Application examples can be found in Section 27.1.8, “Archives and Data Compression” (page 385).
398
locate patterns
This command is only available if you have installed the findutils-locate
package. The locate command can find in which directory a specified file is located. If desired, use wild cards to specify filenames. The program is very speedy,
because it uses a database specifically created for the purpose (rather than searching
through the entire file system). This very fact, however, also results in a major
drawback: locate is unable to find any files created after the latest update of its
database. The database can be generated by root with updatedb.
updatedb [options]
This command performs an update of the database used by locate. To include
files in all existing directories, run the program as root. It also makes sense to
place it in the background by appending an ampersand (&), so you can immediately
continue working on the same command line (updatedb &). This command
usually runs as a daily cron job (see cron.daily).
find [options]
With find, search for a file in a given directory. The first argument specifies the
directory in which to start the search. The option -name must be followed by a
search string, which may also include wild cards. Unlike locate, which uses a
database, find scans the actual directory.
Commands to Access File Contents
cat [options] files
The cat command displays the contents of a file, printing the entire contents to the
screen without interruption.
-n
Numbers the output on the left margin
less [options] files
This command can be used to browse the contents of the specified file. Scroll half
a screen page up or down with PgUp and PgDn or a full screen page down with
Working with the Shell
399
Space . Jump to the beginning or end of a file using
the program.
Home
and
End
. Press
Q
to exit
grep [options] searchstring files
The grep command finds a specific search string in the specified files. If the search
string is found, the command displays the line in which searchstring was found
along with the filename.
-i
Ignores case
-H
Only displays the names of the respective files, but not the text lines
-n
Additionally displays the numbers of the lines in which it found a hit
-l
Only lists the files in which searchstring does not occur
diff [options] file1 file2
The diff command compares the contents of any two files. The output produced
by the program lists all lines that do not match. This is frequently used by programmers who need only send their program alterations and not the entire source code.
-q
Only reports whether the two files differ
-u
Produces a “unified” diff, which makes the output more readable
File Systems
mount [options] [device] mountpoint
This command can be used to mount any data media, such as hard disks, CD-ROM
drives, and other drives, to a directory of the Linux file system.
400
-r
mount read-only
-t filesystem
Specifies the file system, commonly ext2 for Linux hard disks, msdos for
MS-DOS media, vfat for the Windows file system, and iso9660 for CDs
For hard disks not defined in the file /etc/fstab, the device type must also be
specified. In this case, only root can mount it. If the file system should also be
mounted by other users, enter the option user in the appropriate line in the /etc/
fstab file (separated by commas) and save this change. Further information is
available in the mount(1) man page.
umount [options] mountpoint
This command unmounts a mounted drive from the file system. To prevent data
loss, run this command before taking a removable data medium from its drive.
Normally, only root is allowed to run the commands mount and umount. To
enable other users to run these commands, edit the /etc/fstab file to specify
the option user for the respective drive.
27.3.2 System Commands
The following section lists a few of the most important commands needed for retrieving
system information and process and network control.
System Information
df [options] [directory]
The df (disk free) command, when used without any options, displays information
about the total disk space, the disk space currently in use, and the free space on all
the mounted drives. If a directory is specified, the information is limited to the drive
on which that directory is located.
-h
Shows the number of occupied blocks in gigabytes, megabytes, or kilobytes—in
human-readable format
Working with the Shell
401
-T
Type of file system (ext2, nfs, etc.)
du [options] [path]
This command, when executed without any parameters, shows the total disk space
occupied by files and subdirectories in the current directory.
-a
Displays the size of each individual file
-h
Output in human-readable form
-s
Displays only the calculated total size
free [options]
The command free displays information about RAM and swap space usage,
showing the total and the used amount in both categories. See Section 30.1.6, “The
free Command” (page 454) for more information.
-b
Output in bytes
-k
Output in kilobytes
-m
Output in megabytes
date [options]
This simple program displays the current system time. If run as root, it can also
be used to change the system time. Details about the program are available in the
date(1) man page.
402
Processes
top [options]
top provides a quick overview of the currently running processes. Press H to access
a page that briefly explains the main options for customizing the program.
ps [options] [process ID]
If run without any options, this command displays a table of all your own programs
or processes—those you started. The options for this command are not preceded by
hyphen.
aux
Displays a detailed list of all processes, independent of the owner
kill [options] process ID
Unfortunately, sometimes a program cannot be terminated in the normal way. In
most cases, you should still be able to stop such a runaway program by executing
the kill command, specifying the respective process ID (see top and ps). kill
sends a TERM signal that instructs the program to shut itself down. If this does not
help, the following parameter can be used:
-9
Sends a KILL signal instead of a TERM signal, bringing the specified process
to an end in almost all cases
killall [options] processname
This command is similar to kill, but uses the process name (instead of the process
ID) as an argument, killing all processes with that name.
Network
ping [options] hostname or IP address
The ping command is the standard tool for testing the basic functionality of TCP/IP
networks. It sends a small data packet to the destination host, requesting an immediate reply. If this works, ping displays a message to that effect, which indicates
that the network link is basically functioning.
Working with the Shell
403
-c number
Determines the total number of packages to send and ends after they have been
dispatched (by default, there is no limitation set)
-f
flood ping: sends as many data packages as possible; a popular means, reserved
for root, to test networks
-i value
Specifies the interval between two data packages in seconds (default: one second)
nslookup
The domain name system resolves domain names to IP addresses. With this tool,
send queries to name servers (DNS servers).
telnet [options] hostname or IP address [port]
Telnet is actually an Internet protocol that enables you to work on remote hosts
across a network. telnet is also the name of a Linux program that uses this protocol
to enable operations on remote computers.
WARNING
Do not use telnet over a network on which third parties can “eavesdrop”.
Particularly on the Internet, use encrypted transfer methods, such as ssh,
to avoid the risk of malicious misuse of a password (see the man page for
ssh).
Miscellaneous
passwd [options] [username]
Users may change their own passwords at any time using this command. The administrator root can use the command to change the password of any user on the
system.
su [options] [username]
The su command makes it possible to log in under a different username from a
running session. Specify a username and the corresponding password. The password
404
is not required from root, because root is authorized to assume the identity of
any user. When using the command without specifying a username, you are
prompted for the root password and change to the superuser (root).
Use su - to start a login shell for the different user.
halt [options]
To avoid loss of data, you should always use this program to shut down your system.
reboot [options]
Does the same as halt except the system performs an immediate reboot.
clear
This command cleans up the visible area of the console. It has no options.
27.3.3 For More Information
There are many more commands than listed in this chapter. For information about
other commands or more detailed information, the O'Reilly publication Linux in a
Nutshell is recommended.
27.4
The vi Editor
Text editors are still used for many system administration tasks as well as for programming. In the world of Unix, vi stands out as an editor that offers comfortable editing
functions and is more ergonomic than many editors with mouse support.
27.4.1 Operating Modes
Basically, vi makes use of three operating modes: insert mode, command mode, and
extended mode. The keys have different functions depending on the mode. On start-up,
vi is normally set to the command mode. The first thing to learn is how to switch between
the modes:
Working with the Shell
405
Command Mode to Insert Mode
There are many possibilities, including
line under the current line.
A
for append,
I
for insert, or
O
for a new
Insert Mode to Command Mode
Press Esc to exit the insert mode. vi cannot be terminated in insert mode, so it is
important to get used to pressing Esc .
Command Mode to Extended Mode
The extended mode of vi can be activated by entering a colon (:). The extended or
ex mode is similar to an independent line-oriented editor that can be used for various
simple and more complex tasks.
Extended Mode to Command Mode
After executing a command in extended mode, the editor automatically returns to
command mode. If you decide not to execute any command in extended mode, delete
the colon with <— . The editor returns to command mode.
It is not possible to switch directly from insert mode to extended mode without first
switching to command mode.
vi, like other editors, has its own procedure for terminating the program. You cannot
terminate vi while in insert mode. First, exit insert mode by pressing Esc . Subsequently,
you have two options:
1.
Exit without saving: To terminate the editor without saving the changes, enter
: – Q – ! in command mode. The exclamation mark (!) causes vi to ignore any
changes.
2.
Save and exit: There are several possibilities to save your changes and terminate
the editor. In command mode, use Shift + Z + Z . To exit the program saving all
changes using the extended mode, enter : – W – Q . In extended mode, w stands
for writ and q for quit.
27.4.2 vi in Action
vi can be used as a normal editor. In insert mode, enter text and delete text with the
<— and Del keys. Use the arrow keys to move the cursor.
406
However, these control keys often cause problems, because there are many terminal
types that use special key codes. This is where the command mode comes into play.
Press Esc to switch from insert mode to command mode. In command mode, move the
cursor with H , J , K , and L . The keys have the following functions:
H
move one character to the left
J
move one line down
K
move one line up
L
move one character to the right
The commands in command mode allow diverse variations. To execute a command
several times, simply enter the number of repetitions before entering the actual command.
For example, enter 5 L to move the cursor five characters to the right.
A selection of important commands is shown in Table 27.1, “Simple Commands of the
vi Editor” (page 407) This list is far from complete. More complete lists are available
in the documentation found in Section 27.4.3, “For More Information” (page 408)
Table 27.1
Simple Commands of the vi Editor
Esc
Change to command mode
I
Change to insert mode (characters appear at the current cursor
position)
A
Change to insert mode (characters are inserted after the current
cursor position)
Shift
+
A
Changes to insert mode (characters are added at the end of the
line)
Shift
+
R
Change to replace mode (overwrite the old text)
Working with the Shell
407
R
Replace character under the cursor
O
Change to insert mode (a new line is inserted after the current
one)
Shift
+
O
Change to insert mode (a new line is inserted before the current
one)
Delete the current character
X
D
–
D
Delete the current line
D
–
W
Delete up to the end of the current word
C
–
W
Change to insert mode (the rest of the current word is overwritten by the next entries you make)
Undo the last command
U
Ctrl
Shift
.
+
+
R
J
Redo change that was undone
Join the following line with the current one
Repeat the last command
27.4.3 For More Information
vi supports a wide range of commands. It enables the use of macros, shortcuts, named
buffers, and many other useful features. A detailed description of the various options
would exceed the scope of this manual. SUSE Linux comes with vim (vi improved),
an improved version of vi. There are numerous information sources for this application:
• vimtutor is an interactive tutor for vim.
• In vim, enter the command :help to get help for many subjects.
• A book about vim is available online at http://www.truth.sk/vim/
vimbook-OPL.pdf.
408
• The Web pages of the vim project at http://www.vim.org feature all kinds
of news, mailing lists, and other documentation.
• A number of vim sources are available on the Internet: http://www.selflinux
.org/selflinux/html/vim.html, http://www.linuxgazette.com/
node/view/9039, and http://www.apmaths.uwo.ca/~xli/vim/vim
_tutorial.html. See http://linux-universe.com/HOWTO/
Vim-HOWTO/vim-tutorial.html for further links to tutorials.
IMPORTANT: The VIM License
vim is “charityware,” which means that the authors do not charge any money
for the software but encourage you to support a nonprofit project with a
monetary contribution. This project solicits help for poor children in Uganda.
More information is available online at http://iccf-holland.org/index
.html, http://www.vim.org/iccf/, and http://www.iccf.nl/.
Working with the Shell
409
Booting and Configuring a Linux
System
28
Booting a Linux system involves various different components. This chapter outlines
the underlying principles and highlights the components involved. The concept of
runlevels and SUSE's system configuration with sysconfig are also discussed in
this chapter.
28.1
The Linux Boot Process
The Linux boot process consists of several stages each represented by another component. The following list briefly summarizes the boot process and features all the major
components involved.
1.
BIOS After the computer has been turned on, the BIOS initializes the screen
and keyboard and tests the main memory. Up to this stage, the machine does not
access any mass storage media. Subsequently, the information about the current
date, time, and the most important peripherals are loaded from the CMOS values.
When the first hard disk and its geometry are recognized, the system control
passes from the BIOS to the boot loader.
2.
Boot Loader The first physical 512-byte data sector of the first hard disk is
loaded into the main memory and the boot loader that resides at the beginning
of this sector takes over. The commands executed by the boot loader determine
the remaining part of the boot process. Therefore, the first 512 bytes on the first
hard disk are referred to as the Master Boot Record (MBR). The boat loader then
passes control to the actual operating system, in this case, the Linux kernel. More
Booting and Configuring a Linux System
411
information about GRUB, the Linux boot loader, can be found in Chapter 29,
The Boot Loader (page 427).
3.
Kernel and initramfs To pass system control, the boot loader loads both the
kernel and an initial RAM-based file system (initramfs) into memory. The contents of the initial ramfs can be used by the kernel directly. The init ramfs contains
a small executable called init that handles the mounting of the real root file system. In former versions of SUSE Linux, these tasks were handled by initrd and
linuxrc, respectively. For more information about initramfs, refer to Section 28.1.1, “initramfs” (page 412).
4.
init on initramfs This program performs all actions needed to mount the
proper root file system, like providing kernel functionality for the needed file
system and device drivers for mass storage controllers. After the root file system
has been found, it is checked for errors and mounted. If this has been successful,
the initramfs is cleaned and the init program on the root file system is executed.
For more information about init, refer to Section 28.1.2, “init on initramfs”
(page 413).
5.
init init handles the actual booting of the system through several different
levels providing different functionality. init is described in Section 28.2, “The
init Process” (page 414).
28.1.1 initramfs
initramfs is a small file system that the kernel can load to a RAM disk. It provides a
minimal Linux environment that enables the execution of programs before the actual
root file system is mounted. This minimal Linux environment is loaded into memory
by BIOS routines and does not have specific hardware requirements other than sufficient
memory. initramfs must always provide an executable named init that should execute
the actual init program on the root file system for the boot process to proceed.
Before the actual root file system can be mounted and the actual operating system can
be started, the kernel needs the corresponding drivers to access the device on which the
root file system is located. These drivers may include special drivers for certain kinds
of hard drives or even network drivers to access a network file system. The needed
modules for the root file system may be loaded by init on initramfs. initramfs is available
during the entire boot process. This makes it possible to handle all hotplug events generated during boot.
412
If you need to change hardware (hard disks) in an installed system and this hardware
requires different drivers to be present in the kernel at boot time, you must update
initramfs. This is done in the same way as with initramfs' predecessor, initrd, by calling
mkinitrd. Calling mkinitrd without any argument creates an initramfs. Calling
mkinitrd -R creates an initrd. In SUSE Linux, the modules to load are specified
by the variable INITRD_MODULES in /etc/sysconfig/kernel. After installation, this variable is automatically set to the correct value. The modules are loaded in
exactly the order in which they appear in INITRD_MODULES. This is especially important if several SCSI drivers are used, because otherwise the names of the hard disks
would change. Strictly speaking, it would be sufficient just to load those drivers needed
to access the root file system. However, all SCSI drivers needed for installation are
loaded by means of initramfs or initrd because later loading could be problematic.
IMPORTANT: Updating initramfs or initrd
The boot loader loads initramfs or initrd in the same way as the kernel. It is
not necessary to reinstall GRUB after updating initramfs or initrd, because GRUB
searches the directory for the right file when booting.
28.1.2 init on initramfs
The main purpose of init on initramfs is to prepare the mounting of and access to the
real root file system. Depending on your actual system configuration, init is responsible
for the following tasks.
Loading Kernel Modules
Depending on your hardware configuration, special drivers may be needed to access
the hardware components of your computer (the most important component being
your hard drive). To access the final root file system, the kernel needs to load the
proper file system drivers.
Managing RAID and LVM Setups
If you configured your system to hold the root file system under RAID or LVM,
init sets up LVM or RAID to enable access to the root file sytem later. Information
about RAID can be found in Section 2.3, “Soft RAID Configuration” (page 65).
Information about LVM can be found in Section 2.2, “LVM Configuration”
(page 58).
Booting and Configuring a Linux System
413
Managing Network Configuration
If you configured your system to use a network-mounted root file system (mounted
via NFS), init must make sure that the proper network drivers are loaded and that
they are set up to allow access to the root file system.
When init is called during the initial boot as part of the installation process, its tasks
differ from those mentioned earlier:
Finding the Installation Medium
As you start the installation process, your machine loads an installation kernel and
a special initrd with the YaST installer from the installation medium. The YaST
installer, which is run in a RAM file system, needs to have information about the
actual location of the installation medium to access it and install the operating system.
Initiating Hardware Recognition and Loading Appropriate Kernel Modules
As mentioned in Section 28.1.1, “initramfs” (page 412), the boot process starts with
a minimum set of drivers that can be used with most hardware configurations. init
starts an initial hardware scanning process that determines the set of drivers suitable
for your hardware configuration. These values are later written to
INITRD_MODULES in /etc/sysconfig/kernel to enable any subsequent
boot process to use a custom initrd. During the installation process, init loads this
set of modules.
Loading the Installation System or Rescue System
As soon as the hardware has been properly recognized and the appropriate drivers
have been loaded, init starts the installation system, which contains the actual YaST
installer, or the rescue system.
Starting YaST
Finally, init starts YaST, which starts package installation and system configuration.
28.2
The init Process
The program init is the process with process number 1. It is responsible for initializing
the system in the required way. init takes a special role. It is started directly by the
kernel and resists signal 9, which normally kills processes. All other programs are either
started directly by init or by one of its child processes.
414
init is centrally configured in the /etc/inittab file where the runlevels are defined
(see Section 28.2.1, “Runlevels” (page 415)). The file also specifies which services and
daemons are available in each of the levels. Depending on the entries in /etc/
inittab, several scripts are run by init. For reasons of clarity, these scripts, called
init scripts, all reside in the directory /etc/init.d (see Section 28.2.2, “Init Scripts”
(page 418)).
The entire process of starting the system and shutting it down is maintained by init.
From this point of view, the kernel can be considered a background process whose task
is to maintain all other processes and adjust CPU time and hardware access according
to requests from other programs.
28.2.1 Runlevels
In Linux, runlevels define how the system is started and what services are available in
the running system. After booting, the system starts as defined in /etc/inittab in
the line initdefault. Usually this is 3 or 5. See Table 28.1, “Available Runlevels”
(page 415). As an alternative, the runlevel can be specified at boot time (at the boot
prompt, for instance). Any parameters that are not directly evaluated by the kernel itself
are passed to init.
Table 28.1
Available Runlevels
Runlevel
Description
0
System halt
S
Single user mode; from the boot prompt, only with US keyboard
mapping
1
Single user mode
2
Local multiuser mode without remote network (NFS, etc.)
3
Full multiuser mode with network
4
Not used
Booting and Configuring a Linux System
415
Runlevel
Description
5
Full multiuser mode with network and X display manager—KDM, GDM, or XDM
6
System reboot
IMPORTANT: Avoid Runlevel 2 with a /usr Partition Mounted via NFS
You should not use runlevel 2 if your system mounts the /usr partition via
NFS. The /usr directory holds important programs essential for the proper
functioning of the system. Because the NFS service is not available in runlevel 2
(local multiuser mode without remote network), the system would be seriously
restricted in many aspects.
To change runlevels while the system is running, enter init and the corresponding
number as an argument. Only the system administrator is allowed to do this. The following list summarizes the most important commands in the runlevel area.
init 1 or shutdown now
The system changes to single user mode. This mode is used for system maintenance
and administration tasks.
init 3
All essential programs and services (including network) are started and regular users
are allowed to log in and work with the system without a graphical environment.
init 5
The graphical environment is enabled. This can be one of the desktops (GNOME
or KDE) or any window manager.
init 0 or shutdown -h now
The system halts.
init 6 or shutdown -r now
The system halts then reboots.
Runlevel 5 is the default runlevel in all SUSE Linux standard installations. Users are
prompted for login with a graphical interface. If the default runlevel is 3, the X Window
416
System must be configured properly, as described in Chapter 35, The X Window System
(page 509), before the runlevel can be switched to 5. If this is done, check whether the
system works in the desired way by entering init 5. If everything turns out as expected, you can use YaST to set the default runlevel to 5.
WARNING: Errors in /etc/inittab May Result in a Faulty System Boot
If /etc/inittab is damaged, the system might not boot properly. Therefore,
be extremely careful while editing /etc/inittab and always keep a backup
of an intact version. To repair damage, try entering init=/bin/sh after the
kernel name at the boot prompt to boot directly into a shell. After that, make
your root file system writable with the command mount -o remount,rw
/ and replace /etc/inittab with your backup version using cp. To prevent
file system errors, change your root file system to read-only before you reboot
with mount -o remount,ro /.
Generally, two things happen when you change runlevels. First, stop scripts of the
current runlevel are launched, closing down some programs essential for the current
runlevel. Then start scripts of the new runlevel are started. Here, in most cases, a number
of programs are started. For example, the following occurs when changing from runlevel
3 to 5:
1.
The administrator (root) requests init to change to a different runlevel by entering init 5.
2.
init consults its configuration file (/etc/inittab) and determines it should
start /etc/init.d/rc with the new runlevel as a parameter.
3.
Now rc calls all the stop scripts of the current runlevel, but only those for which
there is no start script in the new runlevel. In this example, these are all the scripts
that reside in /etc/init.d/rc3.d (old runlevel was 3) and start with a K.
The number following K specifies the order to start, because there are some dependencies to consider.
4.
The last things to start are the start scripts of the new runlevel. These are, in this
example, in /etc/init.d/rc5.d and begin with an S. The same procedure
regarding the order in which they are started is applied here.
Booting and Configuring a Linux System
417
When changing into the same runlevel as the current runlevel, init only checks /etc/
inittab for changes and starts the appropriate steps, for example, for starting a
getty on another interface.
28.2.2 Init Scripts
There are two types of scripts in /etc/init.d:
Scripts Executed Directly by init
This is the case only during the boot process or if an immediate system shutdown
is initiated (power failure or a user pressing Ctrl + Alt + Del ). The execution of
these scripts is defined in /etc/inittab.
Scripts Executed Indirectly by init
These are run when changing the runlevel and always call the master script
/etc/init.d/rc, which guarantees the correct order of the relevant scripts.
All scripts are located in /etc/init.d. Scripts for changing the runlevel are also
found there, but are called through symbolic links from one of the subdirectories (/etc/
init.d/rc0.d to /etc/init.d/rc6.d). This is just for clarity reasons and
avoids duplicate scripts if they are used in several runlevels. Because every script can
be executed as both a start and a stop script, these scripts must understand the parameters
start and stop. The scripts also understand the restart, reload,
force-reload, and status options. These different options are explained in Table 28.2, “Possible init Script Options” (page 418). Scripts that are run directly by init
do not have these links. They are run independently from the runlevel when needed.
Table 28.2
418
Possible init Script Options
Option
Description
start
Start service.
stop
Stop service.
restart
If the service is running, stop it then restart it. If it is not
running, start it.
Option
Description
reload
Reload the configuration without stopping and restarting
the service.
force-reload
Reload the configuration if the service supports this.
Otherwise, do the same as if restart had been given.
status
Show the current status of service.
Links in each runlevel-specific subdirectory make it possible to associate scripts with
different runlevels. When installing or uninstalling packages, these links are added and
removed with the help of the program insserv (or using /usr/lib/lsb/install
_initd, which is a script calling this program). See the insserv(8) man page for details.
A short introduction to the boot and stop scripts launched first or last, respectively,
follows as well as an explanation of the maintaining script.
boot
Executed while starting the system directly using init. It is independent of the chosen
runlevel and is only executed once. Here, the proc and pts file systems are
mounted and blogd (boot logging daemon) is activated. If the system is booted for
the first time after an update or an installation, the initial system configuration is
started.
The blogd daemon is a service started by boot and rc before any other one. It is
stopped after the actions triggered by the above scripts (running a number of subscripts, for example) are completed. blogd writes any screen output to the log file
/var/log/boot.msg, but only if and when /var is mounted read-write. Otherwise, blogd buffers all screen data until /var becomes available. Get further information about blogd on the blogd(8) man page.
The script boot is also responsible for starting all the scripts in /etc/init.d/
boot.d with a name that starts with S. There, the file systems are checked and
loop devices are configured if needed. The system time is also set. If an error occurs
while automatically checking and repairing the file system, the system administrator
can intervene after first entering the root password. Last executed is the script
boot.local.
Booting and Configuring a Linux System
419
boot.local
Here, enter additional commands to execute at boot before changing into a runlevel.
It can be compared to AUTOEXEC.BAT on DOS systems.
boot.setup
This script is executed when changing from single user mode to any other runlevel
and is responsible for a number of basic settings, such as the keyboard layout and
initialization of the virtual consoles.
halt
This script is only executed while changing into runlevel 0 or 6. Here, it is executed
either as halt or as reboot. Whether the system shuts down or reboots depends
on how halt is called.
rc
This script calls the appropriate stop scripts of the current runlevel and the start
scripts of the newly selected runlevel.
You can create your own scripts and easily integrate them into the scheme described
above. For instructions about formatting, naming, and organizing custom scripts, refer
to the specifications of the LSB and to the man pages of init, init.d, and insserv.
Additionally consult the man pages of startproc and killproc.
WARNING: Faulty init Scripts May Halt Your System
Faulty init scripts may hang your machine. Edit such scripts with great care and,
if possible, subject them to heavy testing in the multiuser environment. Some
useful information about init scripts can be found in Section 28.2.1, “Runlevels”
(page 415).
To create a custom init script for a given program or service, use the file /etc/init
.d/skeleton as a template. Save a copy of this file under the new name and edit
the relevant program and filenames, paths, and other details as needed. You may also
need to enhance the script with your own parts, so the correct actions are triggered by
the init procedure.
The INIT INFO block at the top is a required part of the script and should be edited.
See Example 28.1, “A Minimal INIT INFO Block” (page 421).
420
Example 28.1
A Minimal INIT INFO Block
### BEGIN INIT INFO
# Provides:
# Required-Start:
# Required-Stop:
# Default-Start:
# Default-Stop:
# Description:
### END INIT INFO
FOO
$syslog $remote_fs
$syslog $remote_fs
3 5
0 1 2 6
Start FOO to allow XY and provide YZ
In the first line of the INFO block, after Provides:, specify the name of the program
or service controlled by this init script. In the Required-Start: and
Required-Stop: lines, specify all services that need to be started or stopped before
the service itself is started or stopped. This information is used later to generate the
numbering of script names, as found in the runlevel directories. After
Default-Start: and Default-Stop:, specify the runlevels in which the service
should automatically be started or stopped. Finally, for Description:, provide a
short description of the service in question.
To create the links from the runlevel directories (/etc/init.d/rc?.d/) to the
corresponding scripts in /etc/init.d/, enter the command insserv
new-script-name. The insserv program evaluates the INIT INFO header to create
the necessary links for start and stop scripts in the runlevel directories (/etc/init
.d/rc?.d/). The program also takes care of the correct start and stop order for each
runlevel by including the necessary numbers in the names of these links. If you prefer
a graphical tool to create such links, use the runlevel editor provided by YaST, as described in Section 28.2.3, “Configuring System Services (Runlevel) with YaST”
(page 422).
If a script already present in /etc/init.d/ should be integrated into the existing
runlevel scheme, create the links in the runlevel directories right away with insserv or
by enabling the corresponding service in the runlevel editor of YaST. Your changes
are applied during the next reboot—the new service is started automatically.
Do not set these links manually. If something is wrong in the INFO Block, problems
will arise when insserv is run later for some other service.
Booting and Configuring a Linux System
421
28.2.3 Configuring System Services
(Runlevel) with YaST
After starting this YaST module with YaST → System → System Services (Runlevel),
it displays an overview listing all the available services and the current status of each
service (disabled or enabled). Decide whether to use the module in Simple Mode or in
Expert Mode. The default Simple Mode should be sufficient for most purposes. The left
column shows the name of the service, the center column indicates its current status,
and the right column gives a short description. For the selected service, a more detailed
description is provided in the lower part of the window. To enable a service, select it
in the table then select Enable. The same steps apply to disable a service.
Figure 28.1
System Services (Runlevel)
For detailed control over the runlevels in which a service is started or stopped or to
change the default runlevel, first select Expert Mode. The current default runlevel or
“initdefault” (the runlevel into which the system boots by default) is displayed at the
top. Normally, the default runlevel of a SUSE Linux system is runlevel 5 (full multiuser
mode with network and X). A suitable alternative might be runlevel 3 (full multiuser
mode with network).
422
This YaST dialog allows the selection of one of the runlevels (as listed in Table 28.1,
“Available Runlevels” (page 415)) as the new default. Additionally use the table in this
window to enable or disable individual services and daemons. The table lists the services
and daemons available, shows whether they are currently enabled on your system, and,
if so, for which runlevels. After selecting one of the rows with the mouse, click the
check boxes representing the runlevels (B, 0, 1, 2, 3, 5, 6, and S) to define the runlevels
in which the selected service or daemon should be running. Runlevel 4 is initially undefined to allow creation of a custom runlevel. A brief description of the currently selected service or daemon is provided below the table overview.
With Start, Stop, or Refresh, decide whether a service should be activated. Refresh
status checks the current status. Set or Reset lets you select whether to apply your
changes to the system or to restore the settings that existed before starting the runlevel
editor. Selecting Finish saves the changed settings to disk.
WARNING: Faulty Runlevel Settings May Damage Your System
Faulty runlevel settings may render a system unusable. Before applying your
changes, make absolutely sure that you know their consequences.
28.3
System Configuration via
/etc/sysconfig
The main configuration of SUSE Linux is controlled by the configuration files in /etc/
sysconfig. The individual files in /etc/sysconfig are only read by the scripts
to which they are relevant. This ensures that network settings, for example, only need
to be parsed by network-related scripts. Many other system configuration files are
generated according to the settings in /etc/sysconfig. This task is performed by
SuSEconfig. For example, if you change the network configuration, SuSEconfig might
make changes to the file /etc/host.conf as well, because this is one of the files
relevant for the network configuration. This concept enables you to make basic changes
to your configuration without needing to reboot the system.
There are two ways to edit the system configuration. Either use the YaST sysconfig
Editor or edit the configuration files manually.
Booting and Configuring a Linux System
423
28.3.1 Changing the System Configuration
Using the YaST sysconfig Editor
The YaST sysconfig editor provides an easy-to-use front-end to system configuration.
Without any knowledge of the actual location of the configuration variable you need
to change, you can just use the built-in search function of this module, change the value
of the configuration variable as needed, and let YaST take care of applying these
changes, updating configurations that depend on the values set in sysconfig and
restarting services.
WARNING: Modifying /etc/sysconfig/* Files Can Damage Your Installation
Do not modify the /etc/sysconfig files if you lack previous experience
and knowledge. It could do considerable damage to your system. The files in
/etc/sysconfig include a short comment for each variable to explain what
effect they actually have.
Figure 28.2
System Configuration Using the sysconfig Editor
The YaST sysconfig dialog is split into three parts. The left part of the dialog shows a
tree view of all configurable variables. When you select a variable, the right part displays
424
both the current selection and the current setting of this variable. Below, a third window
displays a short description of the variable's purpose, possible values, the default value,
and the actual configuration file from which this variable originates. The dialog also
provides information about which configuration script is executed after changing the
variable and which new service is started as a result of the change. YaST prompts you
to confirm your changes and informs you which scripts will be executed after you leave
the dialog by selecting Finish. Also select the services and scripts to skip for now, so
they are started later. YaST applies all changes automatically and restarts any services
involved for your changes to take an effect.
28.3.2 Changing the System Configuration
Manually
To manually change the system configuration, proceed as follows
1 Become root.
2 Bring the system into single user mode (runlevel 1) with init 1.
3 Change the configuration files as needed with an editor of your choice.
If you do not use YaST to change the configuration files in /etc/sysconfig,
make sure that empty variable values are represented by two quotation marks
(KEYTABLE="") and that values with blanks in them are enclosed in quotation
marks. Values consisting of one word only do not need to be quoted.
4 Execute SuSEconfig to make sure that the changes take effect.
5 Bring your system back to the previous runlevel with a command like init
default_runlevel. Replace default_runlevel with the default runlevel of the system. Choose 5 if you want to return to full multiuser with network
and X or choose 3 if you prefer to work in full multiuser with network.
This procedure is mainly relevant when changing systemwide settings, such as the
network configuration. Small changes should not require going into single user mode,
but you could still do so to make absolutely sure that all the programs concerned are
correctly restarted.
Booting and Configuring a Linux System
425
TIP: Configuring Automated System Configuration
To disable the automated system configuration by SuSEconfig, set the variable
ENABLE_SUSECONFIG in /etc/sysconfig/suseconfig to no. Do not
disable SuSEconfig if you want to use the SUSE installation support. It is also
possible to disable the autoconfiguration partially.
426
29
The Boot Loader
This chapter describes how to configure GRUB, the boot loader used in SUSE Linux.
A special YaST module is available for performing all settings. If you are not familiar
with the subject of booting in Linux, read the following sections to acquire some
background information. This chapter also describes some of the problems frequently
encountered when booting with GRUB and their solutions.
This chapter focuses on boot management and the configuration of the boot loader
GRUB. The boot procedure as a whole is outlined in Chapter 28, Booting and Configuring a Linux System (page 411). A boot loader represents the interface between machine
(BIOS) and the operating system (SUSE Linux). The configuration of the boot loader
directly impacts the start of the operating system.
The following terms appear frequently in this chapter and might need some explanation:
Master Boot Record
The structure of the MBR is defined by an operating system–independent convention.
The first 446 bytes are reserved for the program code. They typically hold the boot
loader program, in this case, GRUB. The next 64 bytes provide space for a partition
table of up to four entries (see Section “Partition Types” (Chapter 1, Installation
with YaST, ↑Start-Up)). The partition table contains information about the partitioning
of the hard disk and the file system type. The operating system needs this table for
handling the hard disk. The last two bytes of the MBR must contain a static “magic
number” (AA55). An MBR containing a different value is regarded as invalid by
the BIOS and all PC operating systems.
The Boot Loader
427
Boot Sectors
Boot sectors are the first sectors of hard disk partitions with the exception of the
extended partition, which merely serves as a “container” for other partitions. These
boot sectors have 512 bytes of space for code used to boot an operating system installed in the respective partition. This applies to boot sectors of formatted DOS,
Windows, and OS/2 partitions, which also contain some important basic data of the
file system. In contrast, the boot sectors of Linux partitions are initally empty after
setting up a file system. Therefore, a Linux partition is not bootable by itself, even
if it contains a kernel and a valid root file system. A boot sector with valid code for
booting the system has the same magic number as the MBR in its last two bytes
(AA55).
29.1
Boot Management
In the simplest case—if only one operating system is installed on a computer—the boot
loader automaticly takes place in the MBR. If several operating systems are installed
on a computer, the following options are available:
Booting Additional Systems from External Media
One of the operating systems is booted from the hard disk. The other operating
systems are booted by means of a boot manager installed on an external medium
(floppy disk, CD, USB storage medium).
Installing a Boot Manager in the MBR
A boot manager enables concurrent installation and alternate use of several systems
on one computer. Users can select the system to boot during the boot process. To
change to another system, the computer must be rebooted. This is only possible if
the selected boot manager is compatible with the installed operating systems.
29.2
Selecting a Boot Loader
By default, the boot loader GRUB is used in SUSE Linux. However, in some cases and
for special hardware and software constellations, LILO may be more suitable. If you
update from an older SUSE Linux version that uses LILO, LILO is installed.
428
Information about the installation and configuration of LILO is available in the Support
Database under the keyword LILO and in /usr/share/doc/packages/lilo.
29.3
Booting with GRUB
GRUB (Grand Unified Bootloader) comprises two stages. stage1 consists of 512 bytes
and is written to the MBR or the boot sector of a hard disk partition or floppy disk.
Subsequently, stage2 is loaded. This stage contains the actual program code. The only
task of the first stage is to load the second stage of the boot loader.
stage2 is able to access file systems. Currently, Ext2, Ext3, ReiserFS, Minix, and the
DOS FAT file system used by Windows are supported. To a certain extent, JFS, XFS,
and UFS and FFS used by BSD systems are also supported. Since version 0.95, GRUB
is also able to boot from a CD or DVD containing an ISO 9660 standard file system
pursuant to the “El Torito” specification. Even before the system is booted, GRUB can
access file systems of supported BIOS disk devices (floppy disks or hard disks, CD
drives, and DVD drives detected by the BIOS). Therefore, changes to the GRUB configuration file (menu.lst) do not require a reinstallation of the boot manager. When
the system is booted, GRUB reloads the menu file with the valid paths and partition
data of the kernel or the initial RAM disk (initrd) and locates these files.
The actual configuration of GRUB is based on three files that are described below:
/boot/grub/menu.lst
This file contains all information about partitions or operating systems that can be
booted with GRUB. Without this information, the system control cannot be passed
to the operating system.
/boot/grub/device.map
This file translates device names from the GRUB and BIOS notation to Linux device
names.
/etc/grub.conf
This file contains the parameters and options the GRUB shell needs for installing
the boot loader correctly.
The Boot Loader
429
GRUB can be controlled in various ways. Boot entries from an existing configuration
can be selected from the graphical menu (splash screen). The configuration is loaded
from the file menu.lst.
In GRUB, all boot parameters can be changed prior to booting. For example, errors
made when editing the menu file can be corrected in this way. Boot commands can also
be entered interactively at a kind of input prompt (see Section “Editing Menu Entries
during the Boot Procedure” (page 434)). GRUB offers the possibility of determining
the location of the kernel and the initrd prior to booting. In this way, you can even
boot an installed operating system for which no entry exists in the boot loader configuration.
The GRUB shell provides an emulation of GRUB in the installed system. It can be used
to install GRUB or test new settings before applying them. See Section 29.3.4, “The
GRUB Shell” (page 437).
29.3.1 The GRUB Boot Menu
The graphical splash screen with the boot menu is based on the GRUB configuration
file /boot/grub/menu.lst, which contains all information about all partitions or
operating systems that can be booted by the menu.
Every time the system is booted, GRUB loads the menu file from the file system. For
this reason, GRUB does not need to be reinstalled after every change to the file. Use
the YaST boot loader to modify the GRUB configuration as described in Section 29.4,
“Configuring the Boot Loader with YaST” (page 439).
The menu file contains commands. The syntax is very simple. Every line contains a
command followed by optional parameters separated by spaces like in the shell. For
historical reasons, some commands permit an = in front of the first parameter. Comments
are introduced by a hash (#).
To identify the menu items in the menu overview, set a title for every entry. The
text (including any spaces) following the keyword title is displayed as a selectable
option in the menu. All commands up to the next title are executed when this menu
item is selected.
430
The simplest case is the redirection to boot loaders of other operating systems. The
command is chainloader and the argument is usually the boot block of another
partition in GRUB block notation. For example:
chainloader (hd0,3)+1
The device names in GRUB are explained in Section “Naming Conventions for Hard
Disks and Partitions” (page 431). This example specifies the first block of the fourth
partition of the first hard disk.
Use the command kernel to specify a kernel image. The first argument is the path to
the kernel image in a partition. The other arguments are passed to the kernel on the
command line.
If the kernel does not have built-in drivers for access to the root partition, initrd
must be specified with a separate GRUB command whose only argument is the path
to the initrd file. Because the loading address of the initrd is written to the
loaded kernel image, the command initrd must follow immediately after the kernel
command.
The command root simplifies the specification of kernel and initrd files. The only
argument of root is a GRUB device or a partition on a GRUB device. This device is
used for all kernel, initrd, or other file paths for which no device is explicitly specified
until the next root command. This command is not used in the menu.lst file generated during the installation. It merely facilitates manual editing.
The boot command is implied at the end of every menu entry, so it does not need to
be written into the menu file. However, if you use GRUB interactively for booting, you
must enter the boot command at the end. The command itself has no arguments. It
merely boots the loaded kernel image or the specified chain loader.
After writing all menu entries, define one of them as the default entry. Otherwise,
the first one (entry 0) is used. You can also specify a time-out in seconds after which
the default entry should boot. timeout and default usually precede the menu entries.
An example file is described in Section “An Example Menu File” (page 432).
Naming Conventions for Hard Disks and Partitions
The naming conventions GRUB uses for hard disks and partitions differ from those
used for normal Linux devices. In GRUB, the numbering of the partitions starts with
The Boot Loader
431
zero. This means that (hd0,0) is the first partition of the first hard disk. On a common
desktop machine with a hard disk connected as primary master, the corresponding
Linux device name is /dev/hda1.
The four possible primary partitions are assigned the partition numbers 0 to 3. The
logical partitions are numbered from 4:
(hd0,0)
(hd0,1)
(hd0,2)
(hd0,3)
(hd0,4)
(hd0,5)
first primary partition of the first hard disk
second primary partition
third primary partition
fourth primary partition (usually an extended partition)
first logical partition
second logical partition
GRUB does not distinguish between IDE, SCSI, and RAID devices. All hard disks
recognized by the BIOS or other controllers are numbered according to the boot sequence
preset in the BIOS.
Unfortunately, GRUB is not able to map the Linux device names to BIOS device names
exactly. It generates this mapping with the help of an algorithm and saves it to the file
device.map, which can be edited if necessary. Information about the file device
.map is available in Section 29.3.2, “The File device.map” (page 436).
A complete GRUB path consists of a device name written in parentheses and the path
to the file in the file system in the specified partition. The path begins with a slash. For
example, the bootable kernel could be specified as follows on a system with a single
IDE hard disk containing Linux in its first partition:
(hd0,0)/boot/vmlinuz
An Example Menu File
The following example shows the structure of a GRUB menu file. The example installation has a Linux boot partition under /dev/hda5, a root partition under /dev/
hda7, and a Windows installation under /dev/hda1.
gfxmenu (hd0,4)/message
color white/blue black/light-gray
default 0
timeout 8
title linux
kernel (hd0,4)/vmlinuz root=/dev/hda7 vga=791
initrd (hd0,4)/initrd
432
title windows
chainloader(hd0,0)+1
title floppy
chainloader(fd0)+1
title failsafe
kernel (hd0,4)/vmlinuz.shipped root=/dev/hda7 ide=nodma \
apm=off acpi=off vga=normal nosmp maxcpus=0 3
initrd (hd0,4)/initrd.shipped
The first block defines the configuration of the splash screen:
gfxmenu (hd0,4)/message
The background image message is located in /dev/hda5.
color white/blue black/light-gray
Color scheme: white (foreground), blue (background), black (selection), and light
gray (background of the selection). The color scheme has no effect on the splash
screen, only on the customizable GRUB menu that you can access by exiting the
splash screen with Esc .
default 0
The first menu entry title linux is the one to boot by default.
timeout 8
After eight seconds without any user input, GRUB automatically boots the default
entry. To deactivate automatic boot, delete the timeout line. If you set timeout
0, GRUB boots the default entry immediately.
The second and largest block lists the various bootable operating systems. The sections
for the individual operating systems are introduced by title.
• The first entry (title linux) is responsible for booting SUSE Linux. The kernel
(vmlinuz) is located in the first logical partition (the boot partition) of the first
hard disk. Kernel parameters, such as the root partition and VGA mode, are appended here. The root partition is specified according to the Linux naming convention
(/dev/hda7/), because this information is read by the kernel and has nothing to
do with GRUB. The initrd is also located in the first logical partition of the first
hard disk.
The Boot Loader
433
• The second entry is responsible for loading Windows. Windows is booted from the
first partition of the first hard disk (hd0,0). The command chainloader +1
causes GRUB to read and execute the first sector of the specified partition.
• The next entry enables booting from floppy disk without modifying the BIOS settings.
• The boot option failsafe starts Linux with a selection of kernel parameters that
enables Linux to boot even on problematic systems.
The menu file can be changed whenever necessary. GRUB then uses the modified settings during the next boot. Edit the file permanently using YaST or an editor of your
choice. Alternatively, make temporary changes interactively using the edit function of
GRUB. See Section “Editing Menu Entries during the Boot Procedure” (page 434).
Editing Menu Entries during the Boot Procedure
In the graphical GRUB boot menu, select the operating system to boot with the arrow
keys. If you select a Linux system, you can enter additional boot parameters at the boot
prompt. To edit individual menu entries directly, press Esc to exit the splash screen
then press E . Changes made in this way only apply to the current boot and are not
adopted permanently.
IMPORTANT: Keyboard Layout during the Boot Procedure
The US keyboard layout is the only one available when booting.
After activating the editing mode, use the arrow keys to select the menu entry of the
configuration to edit. To make the configuration editable, press E again. In this way,
edit incorrect partitions or path specifications before they have a negative effect on the
boot process. Press Enter to exit the editing mode and return to the menu. Then press
B to boot this entry. Further possible actions are displayed in the help text at the bottom.
To enter changed boot options permanently and pass them to the kernel, open the file
menu.lst as the user root and append the respective kernel parameters to the existing
line, separated by spaces:
title linux
kernel (hd0,0)/vmlinuz root=/dev/hda3 additional parameter
initrd (hd0,0)/initrd
434
GRUB automatically adopts the new parameters the next time the system is booted.
Alternatively, this change can also be made with the YaST boot loader module. Append
the new parameters to the existing line, separated by spaces.
Using Wild Cards to Select the Boot Kernel
Especially when developing or using custom kernels, you must either change the entries
in menu.lst or edit the command line to reflect the current kernel and initrd filenames.
To simplify this procedure, use wild cards to update the kernel list of GRUB dynamically. All kernel images that match a specific pattern are then automatically added to
the list of bootable images. Note that there is no support for this feature.
Activate the wild card option by entering an additional menu entry in menu.lst. To
be useful, all kernel and initrd images must have a common base name and an identifier
that matches the kernel with its associated initrd. Consider the following setup:
initrd-default
initrd-test
vmlinuz-default
vmlinuz-test
In this case, you may add both boot images in one GRUB configuration. To get the
menu entries linux-default and linux-test, the following entry in menu.lst
would be needed:
title linux-*
wildcard (hd0,4)/vmlinuz-*
kernel (hd0,4)/vmlinuz-* root=/dev/hda7 vga=791
initrd (hd0,4)/initrd-*
In this example, GRUB searches the partition (hd0,4) for entries matching the wild
card. These entries are used to generate new GRUB menu entries. In the previous example, GRUB behaves as if the following entries exist in menu.lst:
title linux-default
wildcard (hd0,4)/vmlinuz-default
kernel (hd0,4)/vmlinuz-default root=/dev/hda7 vga=791
initrd (hd0,4)/initrd-default
title linux-test
wildcard (hd0,4)/vmlinuz-test
kernel (hd0,4)/vmlinuz-test root=/dev/hda7 vga=791
initrd (hd0,4)/initrd-test
Problems with this configuration can be expected if filenames are not used consistently
or if one of the expanded files, such as an initrd image, is missing.
The Boot Loader
435
29.3.2 The File device.map
The file device.map maps GRUB device names to Linux device names. In a mixed
system containing IDE and SCSI hard disks, GRUB must try to determine the boot sequence by a special procedure, because GRUB does not have access to the BIOS information on the boot sequence. GRUB saves the result of this analysis in the file /boot/
grub/device.map. For a system on which the boot sequence in the BIOS is set to
IDE before SCSI, the file device.map could appear as follows:
(fd0)
(hd0)
(hd1)
/dev/fd0
/dev/hda
/dev/sda
Because the order of IDE, SCSI, and other hard disks depends on various factors and
Linux is not able to identify the mapping, the sequence in the file device.map can
be set manually. If you encounter problems when booting, check if the sequence in this
file corresponds to the sequence in the BIOS and use the GRUB shell, described in
Section 29.3.4, “The GRUB Shell” (page 437), to modify it temporarily if necessary.
After the Linux system has booted, the file device.map can be edited permanently
with the YaST boot loader module or an editor of your choice.
After manually changing device.map, execute the following command to reinstall
GRUB. This command causes the file device.map to be reloaded and the commands
listed in grub.conf to be executed:
grub --batch < /etc/grub.conf
29.3.3 The File /etc/grub.conf
The third important GRUB configuration file apart from menu.lst and device
.map is /etc/grub.conf. This file contains the parameters and options the command grub needs for installing the boot loader correctly:
root (hd0,4)
install /grub/stage1 d (hd0) /grub/stage2 0x8000 (hd0,4)/grub/menu.lst
quit
Meaning of the individual entries:
root (hd0,4)
This command tells GRUB to apply the following commands to the first logical
partition of the first hard disk (the location of the boot files).
436
install parameter
The command grub should be run with the parameter install. stage1 of the
boot loader should be installed in the MBR of the first hard disk (/grub/stage1
d (hd0)). stage2 should be loaded to the memory address 0x8000
(/grub/stage2 0x8000). The last entry ((hd0,4)/grub/menu.lst) tells
GRUB where to look for the menu file.
29.3.4 The GRUB Shell
GRUB actually exists in two versions: as a boot loader and as a normal Linux program
in /usr/sbin/grub. This program is referred to as the GRUB shell. The functionality to install GRUB as boot loader on a hard disk or floppy disk is integrated in GRUB
in the form of the commands install and setup. This is available in the GRUB
shell when Linux is loaded.
However, the commands setup and install are also available during the boot
procedure before Linux is started. This facilitates the repair of a defective system that
can no longer be booted, because the faulty configuration file of the boot loader can be
circumvented by manually entering parameters. Manually entering parameters during
the boot procedure is also useful for testing new settings without impairing the native
system. Simply enter the experimental configuration file with a syntax similar to that
in menu.lst. Then test the functionality of this entry without changing the existing
configuration file. For example, to test a new kernel, enter the command kernel and
the path to the new kernel. If the boot procedure fails, you can continue using the intact
menu.lst the next time you boot. Similarly, the command line interface can also be
used to boot a system despite a faulty menu.lst file by entering the corrected parameters. In the running system, then enter the correct parameters in menu.lst to make
the system permanently bootable.
The mapping of GRUB devices to Linux device names is only relevant when running
the GRUB shell as a Linux program (by entering grub as described in Section 29.3.2,
“The File device.map” (page 436)). For this purpose, the program reads the file device
.map. For more information, see Section 29.3.2, “The File device.map” (page 436).
The Boot Loader
437
29.3.5 Setting a Boot Password
Even before the operating system is booted, GRUB enables access to file systems. Users
without root permissions can access files in your Linux system to which they have no
access once the system is booted. To block this kind of access or prevent users from
booting certain operating systems, set a boot password.
IMPORTANT: Boot Password and Splash Screen
If you use a boot password for GRUB, the usual splash screen is not displayed.
As the user root, proceed as follows to set a boot password:
1 At the root prompt, enter grub.
2 Encrypt the password in the GRUB shell:
grub> md5crypt
Password: ****
Encrypted: $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/
3 Paste the encrypted string into the global section of the file menu.lst:
gfxmenu (hd0,4)/message
color white/blue black/light-gray
default 0
timeout 8
password --md5 $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/
Now GRUB commands can only be executed at the boot prompt after pressing
P and entering the password. However, users can still boot all operating systems
from the boot menu.
4 To prevent one or several operating systems from being booted from the boot
menu, add the entry lock to every section in menu.lst that should not be
bootable without entering a password. For example:
title linux
kernel (hd0,4)/vmlinuz root=/dev/hda7 vga=791
initrd (hd0,4)/initrd
lock
After rebooting the system and selecting the Linux entry from the boot menu,
the following error message is displayed:
438
Error 32: Must be authenticated
Press Enter to enter the menu. Then press P to get a password prompt. After
entering the password and pressing Enter , the selected operating system (Linux
in this case) should boot.
29.4
Configuring the Boot Loader
with YaST
The easiest way to configure the boot loader in your SUSE Linux system is to use the
YaST module. In the YaST Control Center, select System → Boot Loader Configuration.
As in Figure 29.1, “Configuring the Boot Loader with YaST” (page 439), this shows
the current boot loader configuration of your system and allows you to make changes.
Figure 29.1
Configuring the Boot Loader with YaST
Use the Section Management tab to edit, change, and delete boot loader sections for
the individual operating systems. To add an option, click Add. To change the value of
an existing option, select it with the mouse and click Edit. If you do not want to use an
existing option at all, select it and click Delete. If you are not familiar with boot loader
options, read Section 29.3, “Booting with GRUB” (page 429) first.
The Boot Loader
439
Use the Boot Loader Installation tab to view and change settings related to type, location,
and advanced loader settings.
29.4.1 Boot Loader Type
Set the boot loader type in Boot Loader Installation. The default boot loader in SUSE
Linux is GRUB. To use LILO, proceed as follows:
Procedure 29.2
Changing the Boot Loader Type
1 Select the Boot Loader Installation tab.
2 For Boot Loader, select LILO.
3 In the dialog box that opens, select one of the following actions:
Propose New Configuration
Have YaST propose a new configuration.
Convert Current Configuration
Have YaST convert the current configuration. When converting the configuration, some settings may be lost.
Start New Configuration from Scratch
Write a custom configuration. This action is not available during the installation of SUSE Linux.
Read Configuration Saved on Disk
Load your own /etc/lilo.conf. This action is not available during the
installation of SUSE Linux.
4 Click OK to save the changes
5 Click Finish in the main dialog to apply the changes.
During the conversion, the old GRUB configuration is saved to disk. To use it, simply
change the boot loader type back to GRUB and choose Restore Configuration Saved
before Conversion. This action is available only on an installed system.
440
NOTE: Custom Boot Loader
If you want use a boot loader other than GRUB or LILO, select Do Not Install
Any Boot Loader. Read the documentation of your boot loader carefully before
choosing this option.
29.4.2 Boot Loader Location
To change the location of the boot loader, follow these steps:
Procedure 29.3
Changing the Boot Loader Location
1 Select the Boot Loader Installation tab then select one of the following options
for Boot Loader Location:
Master Boot Record of /dev/hdX
This installs the boot loader in the MBR of a disk. This is recommended
whenever YaST determines the system can be booted this way. X identifies
the hard disk, for example, a, b, c, or d:
hda => ide0 master
hdb => ide0 slave
hdc => ide1 master
hdd => ide1 slave
Boot Sector of Boot Partition /dev/hdXY
The boot sector of the /boot partition. This option is the default if you have
several operating systems installed on your hard drive. The Y stands for the
partition (1, 2, 3, 4, 5, etc.) as in:
/dev/hda1
Boot Sector of Root Partition /dev/hdXY
The boot sector of the / (root) partition. Also use this option if you have
several operating systems installed on your hard drive and want to continue
using your old boot manager.
Other
Use this option to specify the location of the boot loader manually.
2 Click Finish to apply your changes.
The Boot Loader
441
29.4.3 Default System
To change the system that is booted by default, proceed as follows:
Procedure 29.4
Setting the Default System
1 Open the Section Management tab.
2 Select the desired system from the list.
3 Click Set as Default.
4 Click Finish to activate these changes.
29.4.4 Boot Loader Time-Out
The boot loader does not boot the default system immediately. During the time-out,
you can select the system to boot or write some kernel parameters. To set the boot
loader time-out, proceed as follows:
Procedure 29.5
Changing the Boot Loader Time-Out
1 Open the Boot Loader Installation tab.
2 Click Boot Loader Options.
3 Check Show Boot Menu.
4 In Boot Menu, change the value of Boot Menu Time-Out by typing in a new value,
clicking the appropriate arrow key with your mouse, or by using the arrow keys
on the keyboard.
5 Click OK.
6 Click Finish to save the changes.
Set for the boot menu should be displayed permanently without timing out by disabling
Continue Booting after a Time-Out.
442
29.4.5 Security Settings
Using this YaST module, you can also set a password to protect booting. This gives
you an additional level of security.
Procedure 29.6
Setting a Boot Loader Password
1 Open the Boot Loader Installation tab.
2 Click Boot Loader Options.
3 In Password Protection, check Protect Boot Loader with Password and set your
password.
4 Click OK.
5 Click Finish to save the changes.
29.4.6 Disk Order
If your computer has more than one hard disk, you can specify the boot sequence of
the disks to match the BIOS setup of the machine (see Section 29.3.2, “The File device.map” (page 436)). To do so, proceed as follows:
Procedure 29.7
Setting the Disk Order
1 Open the Boot Loader Installation tab.
2 Click Boot Loader Installation Details.
3 If more than one disk is listed, select a disk and click Up or Down to reorder the
displayed disks.
4 Click OK to save the changes.
5 Click Finish to save the changes.
Using this module, you can also replace the master boot record with generic code, which
boots the active partition. Click Replace MBR with Gerneric Code in Disk System Area
The Boot Loader
443
Update. Enable Activate Boot Loader Partition to activate the partition that contains
the boot loader. Click Finish to save the changes.
29.5
Uninstalling the Linux Boot
Loader
YaST can be used to uninstall the Linux boot loader and restore the MBR to the state
it had prior to the installation of Linux. During the installation, YaST automatically
creates a backup copy of the original MBR and restores it on request, overwriting
GRUB.
To uninstall GRUB, start the YaST boot loader module (System → Boot Loader Configuration). In the first dialog, select Reset → Restore MBR of Hard Disk and exit the
dialog with Finish. In the MBR, GRUB is overwritten with the data of the original
MBR.
29.6
Creating Boot CDs
If problems occur booting your system using a boot manager or if the boot manager
cannot be installed on the MBR of your hard disk or a floppy disk, it is also possible
to create a bootable CD with all the necessary start-up files for Linux. This requires a
CD writer installed in your system.
Creating a bootable CD-ROM with GRUB merely requires a special form of stage2
called stage2_eltorito and, optionally, a customized menu.lst. The classic
files stage1 and stage2 are not required.
Create a directory in which to create the ISO image, for example, with cd /tmp and
mkdir iso. Also create a subdirectory for GRUB with mkdir -p
iso/boot/grub. Copy the file stage2_eltorito into the directory grub:
cp /usr/lib/grub/stage2_eltorito iso/boot/grub
Also copy the kernel (/boot/vmlinuz), the initrd (/boot/initrd), and the
file /boot/message to iso/boot/:
444
cp /boot/vmlinuz iso/boot/
cp /boot/initrd iso/boot/
cp /boot/message iso/boot/
To make them available to GRUB, copy the file menu.lst to iso/boot/grub and
adjust the path entries to make them point to a CD-ROM device. Do this by replacing
the device name of the hard disks, listed in the format (hd*), in the pathnames with
the device name of the CD-ROM drive, which is (cd):
gfxmenu (cd)/boot/message
timeout 8
default 0
title Linux
kernel (cd)/boot/vmlinuz root=/dev/hda5 vga=794 resume=/dev/hda1
splash=verbose showopts
initrd (cd)/boot/initrd
Finally, create the ISO image with the following command:
mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot \
-boot-load-size 4 -boot-info-table -o grub.iso iso
Then write the resulting file grub.iso to a CD using your preferred utility.
29.7
The Graphical SUSE Screen
Since SUSE Linux 7.2, the graphical SUSE screen is displayed on the first console if
the option “vga=<value>” is used as a kernel parameter. If you install using YaST, this
option is automatically activated in accordance with the selected resolution and the
graphics card. There are three ways to disable the SUSE screen, if desired:
Disabling the SUSE Screen When Necessary
Enter the command echo 0 >/proc/splash on the command line to disable
the graphical screen. To activate it again, enter echo 1 >/proc/splash.
Disabling the SUSE screen by default.
Add the kernel parameter splash=0 to your boot loader configuration. Chapter 29,
The Boot Loader (page 427) provides more information about this. However, if you
prefer the text mode, which was the default in earlier versions, set vga=normal.
The Boot Loader
445
Completely Disabling the SUSE Screen
Compile a new kernel and disable the option Use splash screen instead of boot logo
in framebuffer support.
TIP
Disabling framebuffer support in the kernel automatically disables the splash
screen as well. SUSE cannot provide any support for your system if you run
it with a custom kernel.
29.8
Troubleshooting
This section lists some of the problems frequently encountered when booting with
GRUB and a short description of possible solutions. Some of the problems are covered
in articles in the Support Database at http://portal.suse.de/sdb/en/index
.html. If your specific problem is not included in this list, use the search dialog of
the Support Database at https://portal.suse.com/PM/page/search.pm
to search for keywords like GRUB, boot, and boot loader.
GRUB and XFS
XFS leaves no room for stage1 in the partition boot block. Therefore, do not
specify an XFS partition as the location of the boot loader. This problem can be
solved by creating a separate boot partition that is not formatted with XFS.
GRUB and JFS
Although technically possible, the combination of GRUB with JFS is problematic.
In this case, create a separate boot partition (/boot) and format it with Ext2. Install
GRUB in this partition.
GRUB Reports GRUB Geom Error
GRUB checks the geometry of connected hard disks when the system is booted.
Sometimes, the BIOS returns inconsistent information and GRUB reports a GRUB
Geom Error. If this is the case, use LILO or update the BIOS. Detailed information
about the installation, configuration, and maintenance of LILO is available in the
Support Database under the keyword LILO.
446
GRUB also returns this error message if Linux was installed on an additional hard
disk that is not registered in the BIOS. stage1 of the boot loader is found and loaded
correctly, but stage2 is not found. This problem can be remedied by registering the
new hard disk in the BIOS.
System Containing IDE and SCSI Hard Disks Does Not Boot
During the installation, YaST may have incorrectly determined the boot sequence
of the hard disks. For example, GRUB may regard /dev/hda as hd0 and /dev/
sda as hd1, although the boot sequence in the BIOS is reversed (SCSI before IDE).
In this case, correct the hard disks during the boot process with the help of the GRUB
command line. After the system has booted, edit device.map to apply the new
mapping permanently. Then check the GRUB device names in the files /boot/
grub/menu.lst and /boot/grub/device.map and reinstall the boot
loader with the following command:
grub --batch < /etc/grub.conf
Booting Windows from the Second Hard Disk
Some operating systems, such as Windows, can only boot from the first hard disk.
If such an operating system is installed on a hard disk other than the first hard disk,
you can effect a logical change for the respective menu entry.
...
title windows
map (hd0) (hd1)
map (hd1) (hd0)
chainloader(hd1,0)+1
...
In this example, Windows is started from the second hard disk. For this purpose,
the logical order of the hard disks is changed with map. This change does not affect
the logic within the GRUB menu file. Therefore, the second hard disk must be
specified for chainloader.
29.9
For More Information
Extensive information about GRUB is available at http://www.gnu.org/
software/grub/. Also refer to the grub info page. You can also search for the
keyword “GRUB” in the Support Database at http://portal.suse.de/sdb/
en/index.html to get information about special issues.
The Boot Loader
447
Special Features of SUSE Linux
30
This chapter starts with information about various software packages, the virtual consoles, and the keyboard layout. We talk about software components like bash, cron,
and logrotate, because they were changed or enhanced during the last release cycles.
Even if they are small or considered of minor importance, users may want to change
their default behavior, because these components are often closely coupled with the
system. The chapter is finished by a section about language and country-specific settings
(I18N and L10N).
30.1
Information about Special
Software Packages
The programs bash, cron, logrotate, locate, ulimit, and free, and the file
resolv.conf are very important for system administrators and many users. Man
pages and info pages are two useful sources of information about commands, but both
are not always available. GNU Emacs is a popular and very configurable text editor.
30.1.1 The Package bash and /etc/profile
Bash is the default shell in SUSE Linux. When used as a login shell, it reads several
initialization files. Bash processes them in the order they appear in this list.
1.
/etc/profile
Special Features of SUSE Linux
449
2.
~/.profile
3.
/etc/bash.bashrc
4.
~/.bashrc
Custom settings can be made in ~/.profile or in ~/.bashrc. To ensure the correct
processing of these files, it is necessary to copy the basic settings from /etc/skel/
.profile or /etc/skel/.bashrc into the home directory of the user. It is recommended to copy the settings from /etc/skel following an update. Execute the
following shell commands to prevent the loss of personal adjustments:
mv
cp
mv
cp
~/.bashrc ~/.bashrc.old
/etc/skel/.bashrc ~/.bashrc
~/.profile ~/.profile.old
/etc/skel/.profile ~/.profile
Then copy personal adjustments back from the *.old files.
30.1.2 The cron Package
If you want to run commands regularly and automatically in the background at predefined
times, cron is the traditional tool to use. cron is driven by specially formatted time tables.
Some of of them come with the system and users can write their own tables if needed.
The cron tables are located in /var/spool/cron/tabs. /etc/crontab serves
as a systemwide cron table. Enter the name of the user who should run the command
directly after the time table. In Example 30.1, “Entry in /etc/crontab” (page 450), root
is entered. Package-specific tables, located in /etc/cron.d, have the same format.
See the cron man page (man cron).
Example 30.1
1-59/5 * * * *
Entry in /etc/crontab
root
test -x /usr/sbin/atrun && /usr/sbin/atrun
You cannot edit /etc/crontab by calling the command crontab -e. This file
must be loaded directly into an editor, modified, then saved.
A number of packages install shell scripts to the directories /etc/cron.hourly,
/etc/cron.daily, /etc/cron.weekly, and /etc/cron.monthly, whose
instructions are controlled by /usr/lib/cron/run-crons. /usr/lib/cron/
450
run-crons is run every 15 minutes from the main table (/etc/crontab). This
guarantees that processes that may have been neglected can be run at the proper time.
To run the hourly, daily, or other periodic maintenance scipts at custom times, remove the time stamp files regulary using of /etc/crontab entries (see Example 30.2,
“/etc/crontab: Remove Time Stamp Files” (page 451), which removes the hourly one
before every full hour, the daily one once a day at 2:14 a.m., etc.).
Example 30.2
/etc/crontab: Remove Time Stamp Files
59
14
29
44
root
root
root
root
*
2
2
2
*
*
*
1
*
*
*
*
*
*
6
*
rm
rm
rm
rm
-f
-f
-f
-f
/var/spool/cron/lastrun/cron.hourly
/var/spool/cron/lastrun/cron.daily
/var/spool/cron/lastrun/cron.weekly
/var/spool/cron/lastrun/cron.monthly
The daily system maintenance jobs have been distributed to various scripts for reasons
of clarity. They are contained in the package aaa_base. /etc/cron.daily contains, for example, the components suse.de-backup-rpmdb, suse
.de-clean-tmp, or suse.de-cron-local.
30.1.3 Log Files: Package logrotate
There are a number of system services (daemons) that, along with the kernel itself,
regularly record the system status and specific events to log files. This way, the administrator can regularly check the status of the system at a certain point in time, recognize
errors or faulty functions, and troubleshoot them with pinpoint precision. These log
files are normally stored in /var/log as specified by FHS and grow on a daily basis.
The logrotate package helps control the growth of these files.
Configuration
Configure logrotate with the file /etc/logrotate.conf. In particular, the
include specification primarily configures the additional files to read. SUSE Linux
ensures that programs that produce log files install individual configation files in /etc/
logrotate.d. For example, such programs come with the packages apache2
(/etc/logrotate.d/apache2) and syslogd (/etc/logrotate.d/
syslog).
Special Features of SUSE Linux
451
Example 30.3
Example for /etc/logrotate.conf
# see "man logrotate" for details
# rotate log files weekly
weekly
# keep 4 weeks worth of backlogs
rotate 4
# create new (empty) log files after rotating old ones
create
# uncomment this if you want your log files compressed
#compress
# RPM packages drop log rotation information into this directory
include /etc/logrotate.d
# no packages own lastlog or wtmp - we'll rotate them here
#/var/log/wtmp {
#
monthly
#
create 0664 root utmp
#
rotate 1
#}
# system-specific logs may be also be configured here.
logrotate is controlled through cron and is called daily by /etc/cron.daily/
logrotate.
IMPORTANT
The create option reads all settings made by the administrator in /etc/
permissions*. Ensure that no conflicts arise from any personal modifications.
30.1.4 The Command locate
locate, a command for quickly finding files, is not included in the standard scope of
installed software. If desired, install the package find-locate. The updatedb process
is started automatically every night or about 15 minutes after booting the system.
452
30.1.5 The Command ulimit
With the ulimit (user limits) command, it is possible to set limits for the use of system
resources and to have these displayed. ulimit is especially useful for limiting the
memory available for applications. With this, an application can be prevented from
using too much memory on its own, which could bring the system to a standstill.
ulimit can be used with various options. To limit memory usage, use the options
listed in Table 30.1, “ulimit: Setting Resources for the User” (page 453).
Table 30.1
ulimit: Setting Resources for the User
-m
Maximum size of physical memory
-v
Maximum size of virtual memory
-s
Maximum size of the stack
-c
Maximum size of the core files
-a
Display of limits set
Systemwide settings can be made in /etc/profile. There, enable creation of core
files, needed by programmers for debugging. A normal user cannot increase the values
specified in /etc/profile by the system administrator, but can make special entries
in ~/.bashrc.
Example 30.4
ulimit: Settings in ~/.bashrc
# Limits of physical memory:
ulimit -m 98304
# Limits of virtual memory:
ulimit -v 98304
Memory amounts must be specified in KB. For more detailed information, see man
bash.
Special Features of SUSE Linux
453
IMPORTANT
Not all shells support ulimit directives. PAM (for instance, pam_limits)
offers comprehensive adjustment possibilities if you depend on encompassing
settings for these restrictions.
30.1.6 The free Command
The free command is somewhat misleading if your goal is to find out how much
RAM is currently being used. That information can be found in /proc/meminfo.
These days, users with access to a modern operating system, such as Linux, should not
really need to worry much about memory. The concept of available RAM dates back
to before the days of unified memory management. The slogan free memory is bad
memory applies well to Linux. As a result, Linux has always made the effort to balance
out caches without actually allowing free or unused memory.
Basically, the kernel does not have direct knowledge of any applications or user data.
Instead, it manages applications and user data in a page cache. If memory runs short,
parts of it are written to the swap partition or to files, from which they can initially be
read with the help of the mmap command (see man mmap).
The kernel also contains other caches, such as the slab cache, where the caches used
for network access are stored. This may explain differences between the counters in
/proc/meminfo. Most, but not all of them, can be accessed via /proc/slabinfo.
30.1.7 The File /etc/resolv.conf
Domain name resolution is handled through the file /etc/resolv.conf. Refer to
Chapter 40, The Domain Name System (page 593).
This file is updated by the script /sbin/modify_resolvconf exclusively, with
no other program having permission to modify /etc/resolv.conf directly. Enforcing this rule is the only way to guarantee that the system's network configuration and
the relevant files are kept in a consistent state.
454
30.1.8 Man Pages and Info Pages
For some GNU applications (such as tar), the man pages are no longer maintained. For
these commands, use the --help option to get a quick overview of the info pages,
which provide more in-depth instructions. info is GNU's hypertext system. Read an
introduction to this system by entering info info. Info pages can be viewed with
Emacs by entering emacs -f info or directly in a console with info. You can
also use tkinfo, xinfo, or the SUSE help system to view info pages.
30.1.9 Settings for GNU Emacs
GNU Emacs is a complex work environment. The following sections cover the configuration files processed when GNU Emacs is started. More information is available at
http://www.gnu.org/software/emacs/.
On start-up, Emacs reads several files containing the settings of the user, system administrator, and distributor for customization or preconfiguration. The initialization file ~/
.emacs is installed to the home directories of the individual users from /etc/skel.
.emacs, in turn, reads the file /etc/skel/.gnu-emacs. To customize the program,
copy .gnu-emacs to the home directory (with cp /etc/skel/.gnu-emacs
~/.gnu-emacs) and make the desired settings there.
.gnu-emacs defines the file ~/.gnu-emacs-custom as custom-file. If users
make settings with the customize options in Emacs, the settings are saved to ~/
.gnu-emacs-custom.
With SUSE Linux, the emacs package installs the file site-start.el in the directory /usr/share/emacs/site-lisp. The file site-start.el is loaded before
the initialization file ~/.emacs. Among other things, site-start.el ensures that
special configuration files distributed with Emacs add-on packages, such as psgml,
are loaded automatically. Configuration files of this type are located in /usr/share/
emacs/site-lisp, too, and always begin with suse-start-. The local system
administrator can specify systemwide settings in default.el.
More information about these files is available in the Emacs info file under Init File:
info:/emacs/InitFile. Information about how to disable loading these files (if
necessary) is also provided at this location.
Special Features of SUSE Linux
455
The components of Emacs are divided into several packages:
• The base package emacs.
• emacs-x11 (usually installed): the program with X11 support.
• emacs-nox: the program without X11 support.
• emacs-info: online documentation in info format.
• emacs-el: the uncompiled library files in Emacs Lisp. These are not required at
runtime.
• Numerous add-on packages can be installed if needed: emacs-auctex (for LaTeX), psgml (for SGML and XML), gnuserv (for client and server operation),
and others.
30.2
Virtual Consoles
Linux is a multiuser and multitasking system. The advantages of these features can be
appreciated even on a stand-alone PC system. In text mode, there are six virtual consoles
available. Switch between them using Alt + F1 to Alt + F6 . The seventh console is
reserved for X and the tenth console shows kernel messages. More or fewer consoles
can be assigned by modifying the file /etc/inittab.
To switch to a console from X without shutting it down, use
Alt + F6 . To return to X, press Alt + F7 .
30.3
Ctrl
+
Alt
+
F1
to
Ctrl
+
Keyboard Mapping
To standardize the keyboard mapping of programs, changes were made to the following
files:
/etc/inputrc
/usr/X11R6/lib/X11/Xmodmap
/etc/skel/.Xmodmap
/etc/skel/.exrc
/etc/skel/.less
/etc/skel/.lesskey
/etc/csh.cshrc
456
/etc/termcap
/usr/lib/terminfo/x/xterm
/usr/X11R6/lib/X11/app-defaults/XTerm
/usr/share/emacs/<VERSION>/site-lisp/term/*.el
These changes only affect applications that use terminfo entries or whose configuration files are changed directly (vi, less, etc.). Applications not shipped with SUSE
Linux should be adapted to these defaults.
Under X, the compose key (multikey) can be accessed using Ctrl + Shift (right). Also
see the corresponding entry in /usr/X11R6/lib/X11/Xmodmap.
Further settings are possible using the X Keyboard Extension (XKB). This extension
is also used by the desktop environments GNOME (gswitchit) and KDE (kxkb).
TIP: For More Information
Information about XKB is available in /etc/X11/xkb/README and the documents listed there.
Detailed information about the input of Chinese, Japanese, and Korean (CJK)
is available at Mike Fabian's page: http://www.suse.de/~mfabian/
suse-cjk/input.html.
30.4
Language and Country-Specific
Settings
SUSE Linux is, to a very large extent, internationalized and can be modified for local
needs in a flexible manner. In other words, internationalization (I18N) allows specific
localizations (L10N). The abbreviations I18N and L10N are derived from the first and
last letters of the words and, in between, the number of letters omitted.
Settings are made with LC_ variables defined in the file /etc/sysconfig/
language. This refers not only to native language support, but also to the categories
Messages (Language), Character Set, Sort Order, Time and Date, Numbers, and Money.
Each of these categories can be defined directly with its own variable or indirectly with
a master variable in the file language (see the locale man page).
Special Features of SUSE Linux
457
RC_LC_MESSAGES, RC_LC_CTYPE, RC_LC_COLLATE, RC_LC_TIME,
RC_LC_NUMERIC, RC_LC_MONETARY
These variables are passed to the shell without the RC_ prefix and represent the
listed categories. The shell profiles concerned are listed below. The current setting
can be shown with the command locale.
RC_LC_ALL
This variable, if set, overwrites the values of the variables already mentioned.
RC_LANG
If none of the previous variables are set, this is the fallback. By default, SUSE Linux
only sets RC_LANG. This makes it easier for users to enter their own values.
ROOT_USES_LANG
A yes or no variable. If it is set to no, root always works in the POSIX environment.
The other variables can be set via the YaST sysconfig editor (see Section 28.3.1,
“Changing the System Configuration Using the YaST sysconfig Editor” (page 424)).
The value of such a variable contains the language code, country code, encoding, and
modifier. The individual components are connected by special characters:
LANG=<language>[[_<COUNTRY>].<Encoding>[@<Modifier>]]
30.4.1 Some Examples
You should always set the language and country codes together. Language settings
follow the standard ISO 639 available at http://www.evertype.com/
standards/iso639/iso639-en.html and http://www.loc.gov/
standards/iso639-2/. Country codes are listed in ISO 3166 available at http://
www.din.de/gremien/nas/nabd/iso3166ma/codlstp1/en_listp1
.html.
It only makes sense to set values for which usable description files can be found in
/usr/lib/locale. Additional description files can be created from the files in
/usr/share/i18n using the command localedef. The description files are part
of the glibc-i18ndata package. A description file for en_US.UTF-8 (for English
and United States) can be created with:
localedef -i en_US -f UTF-8 en_US.UTF-8
458
LANG=en_US.UTF-8
This is the default setting if American English is selected during installation. If you
selected another language, that language is enabled but still with UTF-8 as the
character encoding.
LANG=en_US.ISO-8859-1
This sets the language to English, country to United States, and the character set to
ISO-8859-1. This character set does not support the Euro sign, but it can be
useful sometimes for programs that have not been updated to support UTF-8. The
string defining the charset (ISO-8859-1 in this case) is then evaluated by programs
like Emacs.
[email protected]
The above example explicitly includes the Euro sign in a language setting. Strictly
speaking, this setting is obsolete now, because UTF-8 also covers the Euro symbol.
It is only useful if an application does not support UTF-8, but ISO-8859-15.
SuSEconfig reads the variables in /etc/sysconfig/language and writes the
necessary changes to /etc/SuSEconfig/profile and /etc/SuSEconfig/
csh.cshrc. /etc/SuSEconfig/profile is read or sourced by /etc/
profile. /etc/SuSEconfig/csh.cshrc is sourced by /etc/csh.cshrc.
This makes the settings available systemwide.
Users can override the system defaults by editing their ~/.bashrc accordingly. For
instance, if you do not want to use the systemwide en_US for program messages, include
LC_MESSAGES=es_ES so messages are displayed in Spanish instead.
30.4.2 Settings for Language Support
Files in the category Messages are, as a rule, only stored in the corresponding language
directory (like en) to have a fallback. If you set LANG to en_US and the message file
in /usr/share/locale/en_US/LC_MESSAGES does not exist, it falls back to
/usr/share/locale/en/LC_MESSAGES.
A fallback chain can also be defined, for example, for Breton to French or for Galician
to Spanish to Portuguese:
LANGUAGE="br_FR:fr_FR"
Special Features of SUSE Linux
459
LANGUAGE="gl_ES:es_ES:pt_PT"
If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional
fallback to no):
LANG="nn_NO"
LANGUAGE="nn_NO:nb_NO:no"
or
LANG="nb_NO"
LANGUAGE="nb_NO:nn_NO:no"
Note that in Norwegian, LC_TIME is also treated differently.
One problem that can arise is a separator used to delimit groups of digits not being
recognized properly. This occurs if LANG is set to only a two-letter language code like
de, but the definition file glibc uses is located in /usr/share/lib/de_DE/LC
_NUMERIC. Thus LC_NUMERIC must be set to de_DE to make the separator definition
visible to the system.
30.4.3 For More Information
• The GNU C Library Reference Manual, Chapter “Locales and Internationalization”.
It is included in glibc-info.
• Markus Kuhn, UTF-8 and Unicode FAQ for Unix/Linux, currently at http://
www.cl.cam.ac.uk/~mgk25/unicode.html.
• Unicode-Howto, by Bruno Haible: /usr/share/doc/howto/en/html/
Unicode-HOWTO.html.
460
Printer Operation
31
CUPS is the standard print system in SUSE Linux. CUPS is highly user-oriented. In
many cases, it is compatible with LPRng or can be adapted with relatively little effort.
LPRng is included in SUSE Linux only for reasons of compatibility.
Printers can be distinguished by interface, such as USB or network, and printer language.
When buying a printer, make sure that the printer has an interface that is supported by
the hardware and a suitable printer language. Printers can be categorized on the basis
of the following three classes of printer languages:
PostScript Printers
PostScript is the printer language in which most print jobs in Linux and Unix are
generated and processed by the internal print system. This language is already quite
old and very efficient. If PostScript documents can be processed directly by the
printer and do not need to be converted in additional stages in the print system, the
number of potential error sources is reduced. Because PostScript printers are subject
to substantial license costs, these printers usually cost more than printers without a
PostScript interpreter.
Standard Printer (languages like PCL and ESC/P)
Although these printer languages are quite old, they are still undergoing expansion
to address new features in printers. In the case of known printer languages, the print
system can convert PostScript jobs to the respective printer language with the help
of Ghostscript. This processing stage is referred to as interpreting. The best-known
languages are PCL, which is mostly used by HP printers and their clones, and ESC/P,
which is used by Epson printers. These printer languages are usually supported by
Linux and produce a decent print result. Linux may not be able to address some
functions of extremely new and fancy printers, because the open source developers
Printer Operation
461
may still be working on these features. Except for the hpijs drivers developed by
HP, there are currently no printer manufacturers who develop Linux drivers and
make them available to Linux distributors under an open source license. Most of
these printers are in the medium price range.
Proprietary Printers (usually GDI printers)
Usually only one or several Windows drivers are available for proprietary printers.
These printers do not support any of the common printer languages and the printer
languages they use are subject to change when a new edition of a model is released.
See Section 31.7.1, “Printers without Standard Printer Language Support” (page 477)
for more information.
Before you buy a new printer, refer to the following sources to check how well the
printer you intend to buy is supported:
• http://cdb.suse.de/—the SUSE Linux printer database
• http://www.linuxprinting.org/—the LinuxPrinting.org printer database
• http://www.cs.wisc.edu/~ghost/—the Ghostscript Web page
• /usr/share/doc/packages/ghostscript/catalog.devices—list
of included drivers
The online databases always show the latest Linux support status. However, a Linux
distribution can only integrate the drivers available at production time. Accordingly, a
printer currently rated as “perfectly supported” may not have had this status when the
latest SUSE Linux version was released. Thus, the databases may not necessarily indicate
the correct status, but only provide an approximation.
31.1
Workflow of the Printing
System
The user creates a print job. The print job consists of the data to print plus information
for the spooler, such as the name of the printer or the name of the printer queue, and,
optionally, the information for the filter, such as printer-specific options.
462
A dedicated printer queue exists for every printer. The spooler holds the print job in
the queue until the desired printer is ready to receive data. When the printer is ready,
the spooler sends the data through the filter and back-end to the printer.
The filter converts the data the user wants to print (ASCII, PostScript, PDF, JPEG, etc.)
into printer-specific data (PostScript, PCL, ESC/P, etc.). The features of the printer are
described in the PPD files. A PPD file contains printer-specific options with the parameters needed to enable them on the printer. The filter system makes sure that options
selected by the user are enabled.
If you use a PostScript printer, the filter system converts the data into printer-specific
PostScript. This does not require a printer driver. If you use a non-PostScript printer,
the filter system converts the data into printer-specific data using Ghostscript. This requires a Ghostscript printer driver suitable for your printer. The back-end receives the
printer-specific data from the filter passes it to the printer.
31.2
Methods and Protocols for
Connecting Printers
There are various possibilities for connecting a printer to the system. The configuration
of the CUPS print system does not distinguish between a local printer and a printer
connected to the system over the network. In Linux, local printers must be connected
as described in the manual of the printer manufacturer. CUPS supports serial, USB,
parallel, and SCSI connections. For more information about the printer connection,
read the article CUPS in a Nutshell in the Support Database at http://portal
.suse.com. Find the article by entering cups in the search dialog.
WARNING: Cable Connection to the Machine
When connecting the printer to the machine, do not forget that only USB devices can be plugged in or unplugged during operation. The system should be
shut down before changing other kinds of connections.
Printer Operation
463
31.3
Installing the Software
PPD (PostScript printer description) is the computer language that describes the properties, like resolution, and options, such as the availability of a duplex unit. These descriptions are required for using various printer options in CUPS. Without a PPD file,
the print data would be forwarded to the printer in a “raw” state, which is usually not
desired. During the installation of SUSE Linux, many PPD files are preinstalled to enable
even printers without PostScript support to be used.
To configure a PostScript printer, the best approach is to get a suitable PPD file. Many
PPD files are available in the package manufacturer-PPDs, which is automatically
installed within the scope of the standard installation. See Section 31.6.3, “PPD Files
in Various Packages” (page 474) and Section 31.7.2, “No Suitable PPD File Available
for a PostScript Printer” (page 477).
New PPD files can be stored in the directory /usr/share/cups/model/ or added
to the print system with YaST (see Section “Manual Configuration” (page 465)). Subsequently, the PPD file can be selected during the installation.
Be careful if a printer manufacturer wants you to install entire software packages in
addition to modifying configuration files. First, this kind of installation would result in
the loss of the support provided by SUSE Linux and, second, print commands may
work differently and the system may no longer be able to address devices of other
manufacturers. For this reason, the installation of manufacturer software is not recommended.
31.4
Configuring the Printer
After connecting the printer to the computer and installing the software, install the
printer in the system. This should be done with the tools delivered with SUSE Linux.
Because SUSE Linux puts great emphasis on security, third-party tools often have difficulties with the security restrictions and cause more complications than benefits. See
Section 31.6.1, “CUPS Server and Firewall” (page 471) and Section 31.6.2, “Changes
in the CUPS Print Service” (page 472) for more information about troubleshooting.
464
31.4.1 Local Printers
If an unconfigured local printer is detected when you log in, YaST starts for configuring
it. This uses the same dialogs as the following description of configuration.
To configure the printer, select Hardware → Printer in the YaST control center. This
opens the main printer configuration window, where the detected devices are listed in
the upper part. The lower part lists any queues configured so far. If your printer was
not detected, configure it manually.
IMPORTANT
If the Printer entry is not available in the YaST control center, the
yast2-printer package probably is not installed. To solve this problem,
install the yast2-printer package and restart YaST.
Automatic Configuration
YaST is able to configure the printer automatically if the parallel or USB port can be
set up automatically and the connected printer can be detected. The printer database
must also contain the ID string of the printer that YaST retrieves during the automatic
hardware detection. If the hardware ID differs from the model designation, select the
model manually.
To make sure that everything works properly, each configuration should be checked
with the print test function of YaST. The test page also provides important information
about the configuration tested.
Manual Configuration
If the requirements for automatic configuration are not met or if you want a custom
setup, configure the printer manually. Depending on how successful the autodetection
is and how much information about the printer model is found in the database, YaST
may be able to determine the right settings automatically or at least make a reasonable
preselection.
The following parameters must be configured:
Printer Operation
465
Hardware Connection (Port)
The configuration of the hardware connection depends on whether YaST has been
able to find the printer during hardware autodetection. If YaST is able to detect the
printer model automatically, it can be assumed that the printer connection works
on the hardware level and no settings need to be changed in this respect. If YaST
is unable to autodetect the printer model, there may be some problem with the
connection on the hardware level. In this case, some manual intervention is required
to configure the connection.
In the Printer Configuration dialog, press Add to start the manual configuration
workflow. Here, select your Printer Type (for example USB printer) and, with
Next, enter the Printer Connection and select the device.
Name of the Queue
The queue name is used when issuing print commands. The name should be relatively short and consist of lowercase letters and numbers only. Enter the Name for
printing in the next dialog (Queue name).
Printer Model and PPD File
All printer-specific parameters, such as the Ghostscript driver to use and the printer
filter parameters for the driver, are stored in a PPD (PostScript Printer Description)
file. See Section 31.3, “Installing the Software” (page 464) for more information
about PPD files.
For many printer models, several PPD files are available, for example, if several
Ghostscript drivers work with the given model. When you select a manufacturer
and a model in the next dialog (Printer model), YaST selects the PPD file that corresponds to the printer. If several PPD files are available for the model, YaST defaults
to one of them (normally the one marked recommended). You can change the
chosen PPD file in the next dialog with Edit.
For non-PostScript models, all printer-specific data is produced by the Ghostscript
driver. For this reason, the driver configuration is the single most important factor
determining the output quality. The printout is affected both by the kind of
Ghostscript driver (PPD file) selected and the options specified for it. If necessary,
change additional options (as made available by the PPD file) after selecting Edit.
466
Figure 31.1
Selecting the Printer Model
Always check whether your settings work as expected by printing the test page. If
the output is garbled, for example, with several pages almost empty, you should be
able to stop the printer by first removing all paper then stopping the test from YaST.
If the printer database does not include an entry for your model, you can either add
a new PPD file by selecting Add PPD File to Database, or use a collection of
generic PPD files to make the printer work with one of the standard printer languages.
To do so, select UNKNOWN MANUFACTURER as your printer manufacturer.
Advanced Settings
Normally, you do not need to change any of these settings.
31.4.2 Network Printers
A network printer can support various protocols, some of them even concurrently. Although most of the supported protocols are standardized, some manufacturers expand
(modify) the standard because they test systems that have not implemented the standard
correctly or because they want to provide certain functions that are not available in the
standard. Manufacturers then provide drivers for only a few operating systems, eliminating difficulties with those systems. Unfortunately, Linux drivers are rarely provided.
Printer Operation
467
The current situation is such that you cannot act on the assumption that every protocol
works smoothly in Linux. Therefore, you may have to experiment with various options
to achieve a functional configuration.
CUPS supports the socket, LPD, IPP, and smb protocols. Here is some detailed information about these protocols:
socket
Socket refers to a connection in which the data is sent to an Internet socket without
first performing a data handshake. Some of the socket port numbers that are commonly used are 9100 or 35. An example device URI is
socket://host-printer:9100/.
LPD (line printer daemon)
The proven LPD protocol is described in RFC 1179. Under this protocol, some jobrelated data, such as the ID of the printer queue, is sent before the actual print data
is sent. Therefore, a printer queue must be specified when configuring the LPD
protocol for the data transmission. The implementations of diverse printer manufacturers are flexible enough to accept any name as the printer queue. If necessary, the
printer manual should indicate what name to use. LPT, LPT1, LP1, or similar names
are often used. An LPD queue can also be configured on a different Linux or Unix
host in the CUPS system. The port number for an LPD service is 515. An example
device URI is lpd://host-printer/LPT1.
IPP (Internet printing protocol)
IPP is a relatively new (1999) protocol based on the HTTP protocol. With IPP, more
job-related data is transmitted than with the other protocols. CUPS uses IPP for internal data transmission. This is the preferred protocol for a forwarding queue between two CUPS servers. The name of the print queue is necessary to configure
IPP correctly. The port number for IPP is 631. Example device URIs are
ipp://host-printer/ps and
ipp://host-cupsserver/printers/ps.
SMB (Windows share)
CUPS also supports printing on printers connected to Windows shares. The protocol
used for this purpose is SMB. SMB uses the port numbers 137, 138, and 139.
Example device URIs are
smb://user:[email protected]/server/printer,
smb://user:[email protected]/printer, and smb://server/printer.
468
The protocol supported by the printer must be determined before configuration. If the
manufacturer does not provide the needed information, the command nmap, which
comes with the nmap package, can be used to guess the protocol. nmap checks a host
for open ports. For example:
nmap -p 35,137-139,515,631,9100-10000 printerIP
Configuring CUPS in the Network Using YaST
Network printers should be configured with YaST. YaST facilitates the configuration
and is best equipped to handle the security restrictions in CUPS (see Section 31.6.2,
“Changes in the CUPS Print Service” (page 472)). For guidelines for installation of
CUPS in the network, read the article CUPS in a Nutshell in the Support Database at
http://portal.suse.com.
Start the printer configuration then click Add. If not told otherwise by the network adminstrator try the option Print Directly to a Network Printer and proceed according to
your local requirements.
Configuring with Command Line Tools
Alternatively, CUPS can be configured with command-line tools like lpadmin and
lpoptions. You need a device URI (uniform resource identifier) consisting of a
back-end, such as usb, and parameters, like /dev/usb/lp0. For example, the full
URI could be parallel:/dev/lp0 (printer connected to the first parallel port) or
usb:/dev/usb/lp0 (first detected printer connected to the USB port).
With lpadmin, the CUPS server administrator can add, remove, or manage class and
print queues. To add a printer queue use the following syntax:
lpadmin -p queue -v device-URI \
-P PPD-file -E
Then the device (-v) will be available as queue (-p), using the specified PPD file
(-P). This means that you must know the PPD file and the name of the device if you
want to configure the printer manually.
Do not use -E as the first option. For all CUPS commands, -E as the first argument
sets use of an encrypted connection. To enable the printer, -E must be used as shown
in the following example:
Printer Operation
469
lpadmin -p ps -v parallel:/dev/lp0 -P \
/usr/share/cups/model/Postscript.ppd.gz -E
The following example configures a network printer:
lpadmin -p ps -v socket://192.168.1.0:9100/ -P \
/usr/share/cups/model/Postscript-level1.ppd.gz -E
For more options of lpadmin, see the lpadmin(1) man page.
During system installation, certain options are set as default. These options can be
modified for every print job (depending on the print tool used). Changing these default
options with YaST is also possible. Using command line tools, set default options as
follows:
1 First, list all options:
lpoptions -p queue -l
Example:
Resolution/Output Resolution: 150dpi *300dpi 600dpi
The activated default option is evident from the preceding asterisk (*).
2 Change the option with lpadmin:
lpadmin -p queue -o Resolution=600dpi
3 Check the new setting:
lpoptions -p queue -l
Resolution/Output Resolution: 150dpi 300dpi *600dpi
When a normal user runs lpoptions, settings are written to ~/.lpoptions. root
settings are written to /etc/cups/lpoptions.
31.5
Configuration for Applications
Applications rely on the existing printer queues in the same way as command line tools
do. There is usually no need to reconfigure the printer for a particular application, because you should be able to print from applications using the available queues.
470
To print from the command line, enter lp -d queuename filename, substituting
the corresponding names for queuename and filename.
Some applications rely on the lp command for printing. In this case, enter the correct
command in the application's print dialog, usually without specifying filename, for
example, lp -d queuename. To make this work with KDE programs, enable Print
through an external program. Otherwise you cannot enter the print command.
Tools such as xpp and the KDE program kprinter provide a graphical interface for
choosing among queues and setting both CUPS standard options and printer-specific
options made available through the PPD file. You can use kprinter as the standard
printing interface of non-KDE applications by specifying kprinter or
kprinter --stdin as the print command in the print dialogs of these applications.
The behavior of the application itself determines which of these two commands to
choose. If set up correctly, the application should call the kprinter dialog whenever a
print job is issued from it, so you can use the dialog to select a queue and set other
printing options. This requires that the application's own print setup does not conflict
with that of kprinter and that printing options are only changed through kprinter after
it has been enabled.
31.6
Special Features in SUSE Linux
A number of CUPS features have been adapted for SUSE Linux. Some of the most
important changes are covered here.
31.6.1 CUPS Server and Firewall
There are several ways to configure CUPS as the client of a network server.
1.
For every queue on the network server, you can configure a local queue through
which to forward all jobs to the corresponding network server. Usually, this approach is not recommended, because all client machines must be reconfigured
whenever the configuration of the network server changes.
2.
Print jobs can also be forwarded directly to one network server. For this type of
configuration, do not run a local CUPS daemon. lp or corresponding library
Printer Operation
471
calls of other programs can send jobs directly to the network server. However,
this configuration does not work if you also want to print on a local printer.
3.
The CUPS daemon can listen to IPP broadcast packets that other network servers
send to announce available queues. To use this method, port 631/UDP must be
open for incoming packets.
This is the best CUPS configuration for printing over remote CUPS servers.
However, there is a risk that an attacker sends IPP broadcasts with queues and
the local daemon accesses a counterfeit queue. If it then displays the queue with
the same name as another queue on the local server, the owner of the job may
believe the job is sent to a local server, while in reality it is sent to the attacker's
server.
YaST can find CUPS servers by scanning all network hosts to see if they offer this
service and by listening to IPP broadcasts. The second method is used during the system
installation to find CUPS servers for the proposal. It requires that port 631/UDP be
open for incoming packets. Opening a port to configure access to remote queues using
the second method can be a security risk because an attacker could broadcast a server
that might be accepted by users.
The default setting of the firewall shown in the proposal dialog is to reject IPP broadcasts
on any interface. Accordingly, the second method for detecting remote queues and the
third method for accessing remote queues cannot work. Therefore, the firewall configuration must be modified by marking one of the interfaces as internal, which opens
the port by default, or by explicitly opening the port of an external interface. For
security reasons, no ports are open by default.
The proposed firewall configuration must be modified to enable CUPS to detect remote
queues during installation and access remote servers from the local system during normal
operation. Alternatively, the user can detect CUPS servers by actively scanning the local
network hosts or configure all queues manually. However, because of the reasons
mentioned in the beginning of this section, this method is not recommended.
31.6.2 Changes in the CUPS Print Service
These changes were initially applied for SUSE Linux 9.1.
472
cupsd Runs as the User lp
On start-up, cupsd changes from the user root to the user lp. This provides a much
higher level of security, because the CUPS print service does not run with unrestricted
permissions, only with the permissions needed for the print service.
However, the authentication (the password check) cannot be performed via /etc/
shadow, because lp has no access to /etc/shadow. Instead, the CUPS-specific
authentication via /etc/cups/passwd.md5 must be used. For this purpose, a CUPS
administrator with the CUPS administration group sys and a CUPS password must
be entered in /etc/cups/passwd.md5. To do this, enter the following as root:
lppasswd -g sys -a CUPS-admin-name
This setting is also essential if you want to use the administration Web front-end (CUPS)
or the printer administration tool (KDE).
When cupsd runs as lp, /etc/printcap cannot be generated, because lp is not
permitted to create files in /etc/. Therefore, cupsd generates /etc/cups/
printcap. To ensure that applications that can only read queue names from /etc/
printcap continue to work properly, /etc/printcap is a symbolic link pointing
to /etc/cups/printcap.
When cupsd runs as lp, port 631 cannot be opened. Therefore, cupsd cannot be
reloaded with rccups reload. Use rccups restart instead.
Generalized Functionality for BrowseAllow and
BrowseDeny
The access permissions set for BrowseAllow and BrowseDeny apply to all kinds
of packages sent to cupsd. The default settings in /etc/cups/cupsd.conf are
as follows:
BrowseAllow @LOCAL
BrowseDeny All
and
<Location />
Order Deny,Allow
Deny From All
Allow From 127.0.0.1
Printer Operation
473
Allow From 127.0.0.2
Allow From @LOCAL
</Location>
In this way, only LOCAL hosts can access cupsd on a CUPS server. LOCAL hosts are
hosts whose IP addresses belong to a non-PPP interface (interfaces whose
IFF_POINTOPOINT flags are not set) and whose IP addresses belong to the same
network as the CUPS server. Packets from all other hosts are rejected immediately.
cupsd Activated by Default
In a standard installation, cupsd is activated automatically, enabling comfortable access
to the queues of CUPS network servers without any additional manual actions. The
items in Section “cupsd Runs as the User lp” (page 473) and Section “Generalized
Functionality for BrowseAllow and BrowseDeny” (page 473) are vital preconditions
for this feature, because otherwise the security would not be sufficient for an automatic
activation of cupsd.
31.6.3 PPD Files in Various Packages
The YaST printer configuration sets up the queues for CUPS using only the PPD files
installed in /usr/share/cups/model/ on the system. To find the suitable PPD
files for the printer model, YaST compares the vendor and model determined during
hardware detection with the vendors and models in all PPD files available in /usr/
share/cups/model/ on the system. For this purpose, the YaST printer configuration
generates a database from the vendor and model information extracted from the PPD
files. When you select a printer from the list of vendors and models, receive the PPD
files matching the vendor and model.
The configuration using only PPD files and no other information sources has the advantage that the PPD files in /usr/share/cups/model/ can be modified freely. The
YaST printer configuration recognizes changes and regenerates the vendor and model
database. For example, if you only have PostScript printers, normally you do not need
the Foomatic PPD files in the cups-drivers package or the Gimp-Print PPD files
in the cups-drivers-stp package. Instead, the PPD files for your PostScript
printers can be copied directly to /usr/share/cups/model/ (if they do not already
exist in the manufacturer-PPDs package) to achieve an optimum configuration
for your printers.
474
CUPS PPD Files in the cups Package
The generic PPD files in the cups package have been complemented with adapted
Foomatic PPD files for PostScript level 1 and level 2 printers:
• /usr/share/cups/model/Postscript-level1.ppd.gz
• /usr/share/cups/model/Postscript-level2.ppd.gz
PPD Files in the cups-drivers Package
Normally, the Foomatic printer filter foomatic-rip is used together with Ghostscript
for non-PostScript printers. Suitable Foomatic PPD files have the entries *NickName:
... Foomatic/Ghostscript driver and *cupsFilter: ...
foomatic-rip. These PPD files are located in the cups-drivers package.
YaST prefers a Foomatic PPD file if a Foomatic PPD file with the entry *NickName:
... Foomatic ... (recommended) matches the printer model and the
manufacturer-PPDs package does not contain a more suitable PPD file.
Gimp-Print PPD Files in the cups-drivers-stp
Package
Instead of foomatic-rip, the CUPS filter rastertoprinter from Gimp-Print
can be used for many non-PostScript printers. This filter and suitable Gimp-Print PPD
files are available in the cups-drivers-stp package. The Gimp-Print PPD files
are located in /usr/share/cups/model/stp/ and have the entries *NickName:
... CUPS+Gimp-Print and *cupsFilter: ... rastertoprinter.
PPD Files from Printer Manufacturers in the
manufacturer-PPDs Package
The manufacturer-PPDs package contains PPD files from printer manufacturers
that are released under a sufficiently liberal license. PostScript printers should be configured with the suitable PPD file of the printer manufacturer, because this file enables
the use of all functions of the PostScript printer. YaST prefers a PPD file from the
manufacturer-PPDs package if the following conditions are met:
Printer Operation
475
• The vendor and model determined during the hardware detection match the vendor
and model in a PPD file from the manufacturer-PPDs package.
• The PPD file from the manufacturer-PPDs package is the only suitable PPD
file for the printer model or a there is a Foomatic PPD file with a *NickName:
... Foomatic/Postscript (recommended) entry that also matches the
printer model.
Accordingly, YaST does not use any PPD file from the manufacturer-PPDs
package in the following cases:
• The PPD file from the the manufacturer-PPDs package does not match the
vendor and model. This may happen if the manufacturer-PPDs package contains only one PPD file for similar models, for example, if there is no separate PPD
file for the individual models of a model series, but the model name is specified in
a form like Funprinter 1000 series in the PPD file.
• The Foomatic PostScript PPD file is not recommended. This may be because the
printer model does not operate efficiently enough in PostScript mode, for example,
the printer may be unreliable in this mode because it has too little memory or the
printer is too slow because its processor is too weak. Furthermore, the printer may
not support PostScript by default, for example, because PostScript support is only
available as an optional module.
If a PPD file from the manufacturer-PPDs package is suitable for a PostScript
printer, but YaST cannot configure it for these reasons, select the respective printer
model manually in YaST.
31.7
Troubleshooting
The following sections cover some of the most frequently encountered printer hardware
and software problems and ways to solve or circumvent these problems.
476
31.7.1 Printers without Standard Printer
Language Support
Printers that do not support any common printer language and can only be addressed
with special control sequences are called GDI printers. These printers only work with
the operating system versions for which the manufacturer delivers a driver. GDI is a
programming interface developed by Microsoft for graphics devices. The actual problem
is not the programming interface, but the fact that GDI printers can only be addressed
with the proprietary printer language of the respective printer model.
Some printers can be switched to operate either in GDI mode or one of the standard
printer languages. Some manufacturers provide proprietary drivers for their GDI
printers. The disadvantage of proprietary printer drivers is that there is no guarantee
that these work with the installed print system and that they are suitable for the various
hardware platforms. In contrast, printers that support a standard printer language do
not depend on a special print system version or a special hardware platform.
Instead of spending time trying to make a proprietary Linux driver work, it may be
more cost-effective to purchase a supported printer. This would solve the driver problem
once and for all, eliminating the need to install and configure special driver software
and obtain driver updates that may be required due to new developments in the print
system.
31.7.2 No Suitable PPD File Available for a
PostScript Printer
If the manufacturer-PPDs package does not contain any suitable PPD file for a
PostScript printer, it should be possible to use the PPD file from the driver CD of the
printer manufacturer or download a suitable PPD file from the Web page of the printer
manufacturer.
If the PPD file is provided as a zip archive (.zip) or a self-extracting zip archive (.exe),
unpack it with unzip. First, review the license terms of the PPD file. Then use the
cupstestppd utility to check if the PPD file complies with “Adobe PostScript
Printer Description File Format Specification, version 4.3.” If the utility returns “FAIL,”
the errors in the PPD files are serious and are likely to cause major problems. The
Printer Operation
477
problem spots reported by cupstestppd should be eliminated. If necessary, ask the
printer manufacturer for a suitable PPD file.
31.7.3 Parallel Ports
The safest approach is to connect the printer directly to the first parallel port and to select
the following parallel port settings in the BIOS:
• I/O address: 378 (hexadecimal)
• Interrupt: irrelevant
• Mode: Normal, SPP, or Output Only
• DMA: disabled
If the printer cannot be addressed on the parallel port despite these settings, enter the
I/O address explicitly in accordance with the setting in the BIOS in the form 0x378
in /etc/modprobe.conf. If there are two parallel ports that are set to the I/O addresses 378 and 278 (hexadecimal), enter these in the form 0x378,0x278.
If interrupt 7 is free, it can be activated with the entry shown in Example 31.1,
“/etc/modprobe.conf: Interrupt Mode for the First Parallel Port” (page 478). Before activating the interrupt mode, check the file /proc/interrupts to see which interrupts
are already in use. Only the interrupts currently being used are displayed. This may
change depending on which hardware components are active. The interrupt for the
parallel port must not be used by any other device. If you are not sure, use the polling
mode with irq=none.
Example 31.1
/etc/modprobe.conf: Interrupt Mode for the First Parallel Port
alias parport_lowlevel parport_pc
options parport_pc io=0x378 irq=7
31.7.4 Network Printer Connections
Identifying Network Problems
Connect the printer directly to the computer. For test purposes, configure the printer
as a local printer. If this works, the problems are related to the network.
478
Checking the TCP/IP Network
The TCP/IP network and name resolution must be functional.
Checking a Remote lpd
Use the following command to test if a TCP connection can be established to lpd
(port 515) on host:
netcat -z host 515 && echo ok || echo failed
If the connection to lpd cannot be established, lpd may not be active or there may
be basic network problems.
As the user root, use the following command to query a (possibly very long) status
report for queue on remote host, provided the respective lpd is active and the
host accepts queries:
echo -e "\004queue" \
| netcat -w 2 -p 722 host 515
If lpd does not respond, it may not be active or there may be basic network problems. If lpd responds, the response should show why printing is not possible on
the queue on host. If you receive a response like that in Example 31.2, “Error
Message from the lpd” (page 479), the problem is caused by the remote lpd.
Example 31.2
Error Message from the lpd
lpd: your host does not have line printer access
lpd: queue does not exist
printer: spooling disabled
printer: printing disabled
Checking a Remote cupsd
By default, the CUPS network server should broadcast its queues every 30 seconds
on UDP port 631. Accordingly, the following command can be used to test whether
there is a CUPS network server in the network.
netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID
If a broadcasting CUPS network server exists, the output appears as shown in Example 31.3, “Broadcast from the CUPS Network Server” (page 479).
Example 31.3
Broadcast from the CUPS Network Server
ipp://host.domain:631/printers/queue
Printer Operation
479
The following command can be used to test if a TCP connection can be established
to cupsd (port 631) on host:
netcat -z host 631 && echo ok || echo failed
If the connection to cupsd cannot be established, cupsd may not be active or
there may be basic network problems. lpstat -h host -l -t returns a
(possibly very long) status report for all queues on host, provided the respective
cupsd is active and the host accepts queries.
The next command can be used to test if the queue on host accepts a print job
consisting of a single carriage-return character. Nothing should be printed. Possibly,
a blank page may be ejected.
echo -en "\r" \
| lp -d queue -h host
Troubleshooting a Network Printer or Print Server Box
Spoolers running in a print server box sometimes cause problems when they have
to deal with a lot of print jobs. Because this is caused by the spooler in the print
server box, there is nothing you can do about it. As a work-around, circumvent the
spooler in the print server box by addressing the printer connected to the print
server box directly via TCP socket. See Section 31.4.2, “Network Printers”
(page 467).
In this way, the print server box is reduced to a converter between the various forms
of data transfer (TCP/IP network and local printer connection). To use this method,
you need to know the TCP port on the print server box. If the printer is connected
to the print server box and powered on, this TCP port can usually be determined
with the nmap utility from the nmap package some time after the print server box
is powered on. For example, nmap IP-address may deliver the following output
for a print server box:
Port
23/tcp
80/tcp
515/tcp
631/tcp
9100/tcp
State
open
open
open
open
open
Service
telnet
http
printer
cups
jetdirect
This output indicates that the printer connected to the print server box can be addressed via TCP socket on port 9100. By default, nmap only checks a number of
commonly known ports listed in /usr/share/nmap/nmap-services. To
check all possible ports, use the command nmap
480
-p from_port-to_port IP-address. This may take some time. For further
information, refer to the nmap man page.
Enter a command like
echo -en "\rHello\r\f" | netcat -w 1 IP-address port
cat file | netcat -w 1 IP-address port
to send character strings or files directly to the respective port to test if the printer
can be addressed on this port.
31.7.5 Defective Printouts without Error
Message
For the print system, the print job is completed when the CUPS back-end completes
the data transfer to the recipient (printer). If the further processing on the recipient fails,
for example, if the printer is not able to print the printer-specific data, the print system
does not notice this. If the printer is not able to print the printer-specific data, select a
different PPD file that is more suitable for the printer.
31.7.6 Disabled Queues
If the data transfer to the recipient fails entirely after several attempts, the CUPS backend, such as usb or socket, reports an error to the print system (to cupsd). The
back-end decides whether and how many attempts make sense until the data transfer
is reported as impossible. Because further attempts would be in vain, cupsd disables
printing for the respective queue. After eliminating the cause of the problem, the system
administrator must reenable printing with the command /usr/bin/enable.
31.7.7 CUPS Browsing: Deleting Print Jobs
If a CUPS network server broadcasts its queues to the client hosts via browsing and a
suitable local cupsd is active on the client hosts, the client cupsd accepts print jobs
from applications and forwards them to the cupsd on the server. When cupsd accepts
a print job, it is assigned a new job number. Therefore, the job number on the client
host is different from the job number on the server. Because a print job is usually forwarded immediately, it cannot be deleted with the job number on the client host, because
Printer Operation
481
the client cupsd regards the print job as completed as soon as it has been forwarded
to the server cupsd.
To delete the print job on the server, use a command such as lpstat -h
print-server -o to determine the job number on the server, provided the server
has not already completed the print job (that is, sent it to the printer). Using this job
number, the print job on the server can be deleted:
cancel -h print-server queue-jobnnumber
31.7.8 Defective Print Jobs and Data
Transfer Errors
Print jobs remain in the queues and printing resumes if you switch the printer off and
on or shut down and reboot the computer during the printing process. Defective print
jobs must be removed from the queue with cancel.
If a print job is defective or an error occurs in the communication between the host and
the printer, the printer prints numerous sheets of paper with unintelligible characters,
because it is unable to process the data correctly. To deal with this, follow these steps:
1 To stop printing, remove all paper from ink jet printers or open the paper trays
of laser printers. High-quality printers have a button for canceling the current
printout.
2 The print job may still be in the queue, because jobs are only removed after they
are sent completely to the printer. Use lpstat -o or lpstat -h
print-server -o to check which queue is currently printing. Delete the
print job with cancel queue-jobnumber or cancel -h
print-server queue-jobnumber.
3 Some data may still be transferred to the printer even though the print job has
been deleted from the queue. Check if a CUPS back-end process is still running
for the respective queue and terminate it. For example, for a printer connected
to the parallel port, the command fuser -k /dev/lp0 can be used to terminate all processes that are still accessing the printer (more precisely: the parallel
port).
482
4 Reset the printer completely by switching it off for some time. Then insert the
paper and turn on the printer.
31.7.9 Debugging the CUPS Print System
Use the following generic procedure to locate problems in the CUPS print system:
1 Set LogLevel debug in /etc/cups/cupsd.conf.
2 Stop cupsd.
3 Remove /var/log/cups/error_log* to avoid having to search through
very large log files.
4 Start cupsd.
5 Repeat the action that led to the problem.
6 Check the messages in /var/log/cups/error_log* to identify the cause
of the problem.
31.7.10
For More Information
Solutions to many specific problems are presented in the Support Database. If you experience problems with printers, refer to the Support Database articles Installing a
Printer and Printer Configuration from SUSE Linux 9.2, which you can find by
searching for the keyword printer.
Printer Operation
483
The Hotplug System
32
The hotplug system controls the initialization of most devices in a computer. It is not
only used for devices that can be inserted and removed during operation, but for all
devices that are detected while the system is booting. It works closely together with the
sysfs file system and udev, which are described in Chapter 33, Dynamic Device
Nodes with udev (page 491).
Until the kernel has been booted, only devices that are absolutely necessary, like the
bus system, boot disks, and keyboard, are initialized. The kernel triggers hotplug events
for all devices that were detected. The udevd daemon listens to these events and runs
udev to create the device node and configure the device. For devices that cannot be
detected automatically, like old ISA cards, a static configuration is used.
Apart from a few historic exceptions, most devices are initialized immediately as soon
as they are accessible, either during system boot or when devices are hotplugged. During
initialization, interfaces are registered with the kernel. This registration triggers further
hotplug events that cause an automatic configuration of the respective interface.
In former versions of SUSE Linux, a static set of configuration data was used as the
basis for initializing devices. Any hotplug events were handled by separate scripts,
called agents. With this release of SUSE Linux the hotplug subsystem is integrated into
udev, with udev rules provide the functionality of the former hotplug agents.
The general settings for the hotplug subsystem can be found in /etc/sysconfig/
hotplug. All variables are commented. General device configuration is made depending on matching rules found in /etc/udev/rules.d (see Chapter 33, Dynamic
Device Nodes with udev (page 491)). Configuration files for specific devices are located
in /etc/sysconfig/hardware. The hotplug event callback used in former version
The Hotplug System
485
of SUSE Linux, /proc/sys/kernel/hotplug, is usually empty because udevd
receives hotplug messages via a netlink socket.
32.1
Devices and Interfaces
The hotplug system configures not only devices but also interfaces. A device is commonly connected to a bus and provides the functionality required for an interface. An
interface represents the user-visible abstraction of either the entire or a certain subset
of a device. A device usually requires a device driver in the form of kernel modules to
function properly. Additionally, some higher-level driver might be needed to provide
the interface to the user. Interfaces are mostly represented by device nodes created by
udev. The distinction of devices and interfaces is important for understanding the
overall concept.
Devices entered in the sysfs file system are found under /sys/devices. Interfaces
are located under /sys/class or /sys/block. All interfaces in sysfs should
have a link to their devices. However, there are still some drivers that do not automatically add this link. Without that link, it is unknown to which device this interface belongs
and a suitable configuration cannot be found.
Devices are addressed by means of a device description. This may be the device path
in sysfs (/sys/devices/pci0000:00/0000:00:1e.0/0000:02:00.0),
a description of the connection point (bus-pci-0000:02:00.0), an individual ID
(id-32311AE03FB82538), or something similar. In the past, interfaces were addressed by means of their names. These names represented a simple numbering of the
existing devices and might have changed when devices were added or removed.
Interfaces can also be addressed by means of a description of the associated device.
Usually, the context indicates whether the description refers to the device itself or to
its interface. Typical examples of devices, interfaces, and descriptions include:
PCI Network Card
A device that is connected to the PCI bus (/sys/devices/pci0000:00/
0000:00:1e.0/0000:02:00.0 or bus-pci-0000:02:00.0) and has a
network interface (eth0, id-00:0d:60:7f:0b:22 or bus-pci-0000:02:
00.0). The network interface is used by network services or connected to a virtual
network device, such as a tunnel or VLAN, which in turn has an interface.
486
PCI SCSI Controller
A device (/sys/devices/pci0000:20/0000:20:01.1/host1/1:0:
0:0 or bus-scsi-1:0:0:0) that makes several physical interfaces available
in the form of a bus (/sys/class/scsi_host/host1).
SCSI Hard Disk
A device (/sys/devices/pci0000:20/0000:20:01.1/host1/1:0:
0:0 or bus-scsi-1:0:0:0) with several interfaces (/sys/block/sda*).
32.2
Hotplug Events
Every device and every interface has an associated hotplug event, which is processed
by udev. Hotplug events are triggered by the kernel when a link to a device is established or removed or when a driver registers or deletes an interface. Since SUSE Linux
9.3, udevd receives and processes hotplug events. Either udevd listens directly to
netlink messages from the kernel or /sbin/udevsend must be specified in /proc/
sys/kernel/hotplug. udevd configures the device according to a set of rules
(see Chapter 33, Dynamic Device Nodes with udev (page 491)).
32.3
Hotplug Device Configuration
Hotplug agents have been deprecated as of SUSE Linux 10.0. All device configuration
should now be done via udev rules. udev provides a compability rule to call existing
custom agents. However, converting custom agents into udev rules should be considered.
A hotplug agent is an executable program that performs suitable actions for an event.
The agents for device events are located in /etc/hotplug.d/event name and
/etc/hotplug.d/default. All programs in these directories that have the suffix
.hotplug are executed in alphabetical order.
To facilitate device configuration it is usually sufficient to load a kernel module. In
some cases, additional commands need to be called for a proper device configuration.
In SUSE Linux, this is handled generally by udev rules. However, if a custom device
configuration is required, the device configuration is done by /sbin/hwup or /sbin/
hwdown. These programs search for a configuration suitable for the device in the directory /etc/sysconfig/hardware and apply it. For example, to prevent a specific
device from being initialized, create a configuration file with an appropriate name and
The Hotplug System
487
set the start mode to manual or off. If /sbin/hwup does not find any configuration,
it looks for the environment variable MODALIAS. If it exists, modprobe automatically
loads the corresponding module. The MODALIAS variable is automatically generated
by kernel hotplug events for devices that require a module to be loaded. For more information, see Section 32.4, “Automatic Module Loading” (page 489). More information
about /sbin/hwup is available in the file /usr/share/doc/packages/
sysconfig/README and in the manual page man hwup.
Before interface agents are called, udev usually generates a device node the system
can access. udev enables the assignment of persistent names to interfaces. See Chapter 33, Dynamic Device Nodes with udev (page 491) for details. The interfaces itself
are then set up according to the respective udev rules. The procedures for some interfaces
are described below.
32.3.1 Activating Network Interfaces
Network interfaces are initialized with /sbin/ifup and deactivated with /sbin/
ifdown. Details are provided in the file /usr/share/doc/packages/
sysconfig/README and in the ifup man page.
If a computer has several network devices with different drivers, the designations of
the interface can change if another driver is loaded faster while the system is booting.
SUSE Linux tries to keep the numbering persistent—the devices retain the interface
name they have been assigned during configuration. This assigment is done via udev
rules. To change the assignment later, the udev rules must be changed.
The best solution, however, is to use persistent interface designations. You can specify
the names of the individual interfaces in the configuration files. Details about this
method are available in the file /usr/share/doc/packages/sysconfig/
README. Since SUSE Linux 9.3, udev also deals with network interfaces, although
these are not device nodes. This allows use of persistent interface names in a more
standardized manner.
32.3.2 Activating Storage Devices
Interfaces to storage devices must be mounted to be able to access them. This can be
fully automated or preconfigured. Additionally, SUSE Linux distinguishes between
system and user devices. System devices can only be automatically mounted by creating
488
an entry in /etc/fstab. User devices are handled via hal by default. If a different
configuration for user devices is required, these devices can be entered into /etc/
fstab. Alternatively, the handling of this device in hal can be modified. For more
information about hal, refer to /usr/share/doc/packages/hal/hal-spec
.html.
The use of persistent device names is recommended, because traditional device names
may change depending on the initialization sequence. Details about persistent device
names is available in Chapter 33, Dynamic Device Nodes with udev (page 491).
32.4
Automatic Module Loading
If /sbin/hwup fails to detect a configuration file, modprobe searches for a corresponding module based on the contents of the environment variable MODALIAS. This environment variable is generated by the kernel for the corresponding hotplug event. To
use a driver other than the standard driver for the kernel, an appropriate hardware configuration file in /etc/sysconfig/hardware should be created.
32.5
The Boot Script Coldplug
boot.coldplug is responsible for initializing all devices that have not been configured during boot. It calls hwup for every static device configuration designated as
/etc/sysconfig/hardware/hwcfg-static-*. After this, it replays all events
stored in /lib/klibc/events to initialize all devices.
32.6
Error Analysis
32.6.1 Log Files
Unless otherwise specified, hotplug only sends a few important messages to syslog.
To obtain more information, set the variable HOTPLUG_DEBUG in the file /etc/
sysconfig/hotplug to yes. If you set this variable to the value max, every shell
command is logged for all hotplug scripts. This means that /var/log/messages
in which syslog stores all the messages becomes much larger. Because syslog is
The Hotplug System
489
launched during the boot process after hotplug and coldplug, it is possible, however, for the first messages not to be logged. If these messages are important to you,
specify a different log file via the variable HOTPLUG_SYSLOG. Information about this
topic is available in /etc/sysconfig/hotplug.
32.6.2 Boot Problems
If a computer hangs during the boot process, disable hotplug or coldplug by entering NOHOTPLUG=yes or NOCOLDPLUG=yes at the boot prompt. Due to the deactivation of hotplug, the kernel does not issue any hotplug events. In the running system,
you can activate hotplug by entering the command /etc/init.d/boot.hotplug
start. All events generated up to that time are then issued and processed. To reject
the queued events, first enter /bin/true in /proc/sys/kernel/hotplug and
reset the entry to /sbin/hotplug after some time. Because of the deactivation of
coldplug, static configurations are not applied. To apply the static configurations, later
enter /etc/init.d/boot.coldplug start.
To find out whether a particular module loaded by hotplug is responsible for the
problem, enter HOTPLUG_TRACE=<N> at the boot prompt. The names of all the
modules to load are then listed on the screen before they are actually loaded after N
seconds. You cannot intervene while this is going on.
32.6.3 The Event Recorder
The script /sbin/hotplugeventrecorder is executed for every event by a udev
rule. If a directory /events exists, all hotplug events are stored as individual files in
this directory. Thus, events can be regenerated for test purposes. If this directory does
not exist, nothing is recorded.
490
Dynamic Device Nodes with udev
33
Linux kernel 2.6 introduces a new user space solution for a dynamic device directory
/dev with persistent device designations: udev. It provides only the files for devices
that are actually present. It creates or removes device node files usually located in the
/dev directory and is able to rename network interfaces. The previous implementation
of a dynamic /dev with devfs has been replaced by udev.
Traditionally, device nodes were stored in the /dev directory on Linux systems. There
was a node for every possible type of device, regardless of whether it actually existed
in the system. As a result, this directory contained thousands of unused files. Before a
newly added subsystem or kernel device was usable, the corresponding nodes needed
to be created with an special application. The devfs file system brought a significant
improvement, because only devices that actually existed and were known to the kernel
were given a device node in /dev.
udev introduces a new way of creating device nodes. The kernel exports its internal
state in sysfs and, every time a device is recognized by the kernel, it updates the information in sysfs and sends an event to user space. With the information made
available by sysfs udev matches a simple rule syntax with the provided device attributes and creates or removes the corresponding device nodes.
The user is not required to create any udev rule for new devices. If a device is connected,
the appropriate device node is created automatically. However, the rules introduce the
possibility of defining a policy for device naming. This also offers the convenience of
replacing a cryptic device name with a name that is easy to remember and also of having
persistent device names where two devices of the same type have been connected at
the same time.
Dynamic Device Nodes with udev
491
Assume you have two printers, a high-quality color laser printer and a black-and-white
ink jet printer, both connected via USB. They appear as /dev/usb/lpX, where X is
a number depending on the order in which they have been connected. Using udev,
create custom udev rules naming one printer /dev/colorlaser and the other /dev/
inkprinter. Because these device nodes are created by udev based on the characteristics of the device, they always point to the correct device, regardless of the connection
order or status.
33.1
Creating Rules
Before udev creates device nodes under /dev, it reads all files in /etc/udev/
rules.d with the suffix .rules in alphabetical order. The first rule that fits a device
is used, even if other rules would also apply. Comments are introduced with a hash sign
(#). Rules take the following form:
key, [key,...] NAME [, SYMLINK]
At least one key must be specified, because rules are assigned to devices on the basis
of these keys. It is also essential to specify a name. The device node that is created in
/dev bears this name. The optional symlink parameter allows nodes to be created in
other places. A rule for a printer could take the following form:
BUS=="usb", SYSFS{serial}=="12345", NAME="lp_hp", SYMLINK+="printers/hp"
In this example, there are two keys, BUS and SYSFS{serial}. udev compares the
serial number to the serial number of the device that is connected to the USB bus. To
assign the name lp_hp to the device in the /dev directory, all the keys must be
identical. In addition, a symbolic link /dev/printers/hp, which refers to the device
node, is created. At the same time, the printers directory is automatically created.
Print jobs can then be sent to /dev/printers/hp or /dev/lp_hp.
33.2
Placeholder Substitution
The parameters NAME and SYMLINK allow the use of placeholders to substitute special
values. A simple example illustrates the procedure:
BUS=="usb", SYSFS{vendor}=="abc", SYSFS{model}=="xyz", NAME="camera%n"
492
The operator %n in the name is replaced by the number of the camera device, such as
camera0 or camera1. Another useful operator is %k, which is replaced by the standard
device name of the kernel, for example, hda1. You may also call an external program
in udev rules and use the string that is returned in the NAME and SYMLINK values. The
complete list of possible placeholders is described in the udev man page.
33.3
Pattern Matching in Keys
In the keys of udev rules, you may use shell-style pattern matching, known as wild
cards. For example, the character * can be used as a placeholder for any characters or
? can be used for precisely one arbitrary character.
KERNEL="ts*", NAME="input/%k"
This rule assigns the standard kernel name in the standard directory to a device whose
designation begins with the letters “ts”. Find detailed information about the use of pattern
matching in udev rules in the udev man page.
33.4
Key Selection
To identify a device uniquely and distinguish multiple devices from each other, a unique
property is essential for a working udev rule. Here are some examples of standard keys:
SUBSYSTEM
Subsystem of which the device is part
BUS
Device bus type
KERNEL
Device name the kernel uses
ID
Device number on the bus (for example, PCI bus ID)
SYSFS{...}
sysfs device attributes, like label, vendor, or serial number
Dynamic Device Nodes with udev
493
The keys SUBSYSTEM and ID can be useful, but usually the keys BUS, KERNEL, and
SYSFS{...} are used. The udev configuration also provides keys that call external
scripts and evaluate their results. Find details about this in the udev man page.
The file system sysfs exposes information about the hardware in a directory tree.
Each file generally only contains one item of information, such as the device name, the
vendor, or the serial number. Each of these files can be used to match with a key. To
use several SYSFS keys in one rule, however, you can only use files in the same directory as key values. The tool udevinfo can help finding useful and unique key values.
You must find one subdirectory of /sys that refers to the relevant device and contains
a file dev. These directories are all located under /sys/block or /sys/class. If
a device node already exists for the device, udevinfo can find the right subdirectory
for you. The command udevinfo -q path -n /dev/sda outputs /block/sda.
This means that the desired directory is /sys/block/sda. Now call udevinfo
with the command udevinfo -a -p /sys/block/sda. The two commands
can also be combined, as in udevinfo -a -p `udevinfo -q path -n
/dev/sda`. The following is an extract from the output:
BUS=="scsi"
ID=="0:0:0:0"
SYSFS{detach_state}=="0"
SYSFS{type}=="0"
SYSFS{max_sectors}=="240"
SYSFS{device_blocked}=="0"
SYSFS{queue_depth}=="1"
SYSFS{scsi_level}=="3"
SYSFS{vendor}==" "
SYSFS{model}=="USB 2.0M DSC"
SYSFS{rev}=="1.00"
SYSFS{online}=="1"
From the output information, look for suitable keys that do not change. Remember that
you cannot use keys from different directories in one rule.
33.5
Persistent Names for Mass
Storage Devices
SUSE Linux comes with predefined rules that allow you always to assign the same
designations to hard disks and other storage devices, no matter in which order they are
initialized. Unique device attributes, like hardware serial numbers, UUIDs or file system
494
labels, can be read with small helper programs that come with udev. The helper programs
make specific device information available to the udev rule processing. As a simplified
example, the first rule imports the values gathered from the SCSI device in the udev
environment. The second rule uses the imported values to create a persistent symlink.
KERNEL="sd*[!0-9]", IMPORT="/sbin/scsi_id -g -x -s $p -d %N"
KERNEL="sd*[!0-9]", SYMLINK+="$env{ID_TYPE}/by-id/$env{ID_BUS}-$env{ID_SERIAL}"
As soon as a driver for a mass storage device has been loaded, it registers all the available
hard disks with the kernel. Each of them triggers a hotplug block event that calls udev.
Then udev reads the rules to determine whether a symlink needs to be created.
If the driver is loaded via initrd, the hotplug events are lost. However, all the information is stored in sysfs. The udevstart utility finds all the device files under
/sys/block and /sys/class and starts udev.
There is also a start script boot.udev, which recreates all the device nodes during
the boot process. However, the start script must be activated through the YaST runlevel
editor or with the command insserv boot.udev.
Dynamic Device Nodes with udev
495
34
File Systems in Linux
Linux supports a number of different file systems. This chapter presents a brief overview
of the most popular Linux file systems, elaborating on their design concept, advantages,
and fields of application. Some additional information about LFS (large file support)
in Linux is also provided.
34.1
Terminology
metadata
A file system–internal data structure that assures all the data on disk is properly organized and accessible. Essentially, it is “data about the data.” Almost every file
system has its own structure of metadata, which is part of why the file systems show
different performance characteristics. It is extremely important to maintain metadata
intact, because otherwise all data on the file system could become inaccessible.
inode
Inodes contain various information about a file, including size, number of links,
date and time of creation, modification, and access, and pointers to the disk blocks
where the file contents are actually stored.
journal
In the context of a file system, a journal is an on-disk structure containing a kind of
log in which the file system stores what it is about to change in the file system's
metadata. Journaling greatly reduces the recovery time of a Linux system because
it obsoletes the lengthy search process that checks the entire file system at system
start-up. Instead, only the journal is replayed.
File Systems in Linux
497
34.2
Major File Systems in Linux
Unlike two or three years ago, choosing a file system for a Linux system is no longer
a matter of a few seconds (Ext2 or ReiserFS?). Kernels starting from 2.4 offer a variety
of file systems from which to choose. The following is an overview of how these file
systems basically work and which advantages they offer.
It is very important to bear in mind that there may be no file system that best suits all
kinds of applications. Each file system has its particular strengths and weaknesses,
which must be taken into account. Even the most sophisticated file system cannot substitute for a reasonable backup strategy, however.
The terms data integrity and data consistency, when used in this chapter, do not refer
to the consistency of the user space data (the data your application writes to its files).
Whether this data is consistent must be controlled by the application itself.
IMPORTANT: Setting Up File Systems
Unless stated otherwise in this chapter, all the steps required to set up or
change partitions and file systems can be performed using the YaST module.
34.2.1 ReiserFS
Officially one of the key features of the 2.4 kernel release, ReiserFS has been available
as a kernel patch for 2.2.x SUSE kernels since SUSE Linux version 6.4. ReiserFS was
designed by Hans Reiser and the Namesys development team. It has proven itself to
be a powerful alternative to the old Ext2. Its key assets are better disk space utilization,
better disk access performance, and faster crash recovery.
ReiserFS's strengths, in more detail, are:
Better Disk Space Utilization
In ReiserFS, all data is organized in a structure called B*-balanced tree. The tree
structure contributes to better disk space utilization because small files can be stored
directly in the B* tree leaf nodes instead of being stored elsewhere and just maintaining a pointer to the actual disk location. In addition to that, storage is not allocated
in chunks of 1 or 4 kB, but in portions of the exact size needed. Another benefit lies
in the dynamic allocation of inodes. This keeps the file system more flexible than
498
traditional file systems, like Ext2, where the inode density must be specified at file
system creation time.
Better Disk Access Performance
For small files, file data and “stat_data” (inode) information are often stored next
to each other. They can be read with a single disk I/O operation, meaning that only
one access to disk is required to retrieve all the information needed.
Fast Crash Recovery
Using a journal to keep track of recent metadata changes makes a file system check
a matter of seconds, even for huge file systems.
Reliability through Data Journaling
ReiserFS also supports data journaling and ordered data modes similar to the concepts
outlined in the Ext3 section, Section 34.2.3, “Ext3” (page 500). The default mode
is data=ordered, which ensures both data and metadata integrity, but uses
journaling only for metadata.
34.2.2 Ext2
The origins of Ext2 go back to the early days of Linux history. Its predecessor, the
Extended File System, was implemented in April 1992 and integrated in Linux 0.96c.
The Extended File System underwent a number of modifications and, as Ext2, became
the most popular Linux file system for years. With the creation of journaling file systems
and their astonishingly short recovery times, Ext2 became less important.
A brief summary of Ext2's strengths might help understand why it was—and in some
areas still is—the favorite Linux file system of many Linux users.
Solidity
Being quite an “old-timer,” Ext2 underwent many improvements and was heavily
tested. This may be the reason why people often refer to it as rock-solid. After a
system outage when the file system could not be cleanly unmounted, e2fsck starts
to analyze the file system data. Metadata is brought into a consistent state and
pending files or data blocks are written to a designated directory (called lost
+found). In contrast to journaling file systems, e2fsck analyzes the entire file
system and not just the recently modified bits of metadata. This takes significantly
longer than checking the log data of a journaling file system. Depending on file
system size, this procedure can take half an hour or more. Therefore, it is not desir-
File Systems in Linux
499
able to choose Ext2 for any server that needs high availability. However, because
Ext2 does not maintain a journal and uses significantly less memory, it is sometimes
faster than other file systems.
Easy Upgradability
The code for Ext2 is the strong foundation on which Ext3 could become a highlyacclaimed next-generation file system. Its reliability and solidity were elegantly
combined with the advantages of a journaling file system.
34.2.3 Ext3
Ext3 was designed by Stephen Tweedie. Unlike all other next-generation file systems,
Ext3 does not follow a completely new design principle. It is based on Ext2. These two
file systems are very closely related to each other. An Ext3 file system can be easily
built on top of an Ext2 file system. The most important difference between Ext2 and
Ext3 is that Ext3 supports journaling. In summary, Ext3 has three major advantages to
offer:
Easy and Highly Reliable Upgrades from Ext2
Because Ext3 is based on the Ext2 code and shares its on-disk format as well as its
metadata format, upgrades from Ext2 to Ext3 are incredibly easy. Unlike transitions
to other journaling file systems, such as ReiserFS, JFS, or XFS, which can be quite
tedious (making backups of the entire file system and recreating it from scratch), a
transition to Ext3 is a matter of minutes. It is also very safe, because recreating an
entire file system from scratch might not work flawlessly. Considering the number
of existing Ext2 systems that await an upgrade to a journaling file system, you can
easily figure out why Ext3 might be of some importance to many system administrators. Downgrading from Ext3 to Ext2 is as easy as the upgrade. Just perform a
clean unmount of the Ext3 file system and remount it as an Ext2 file system.
Reliability and Performance
Some other journaling file systems follow the “metadata-only” journaling approach.
This means your metadata is always kept in a consistent state, but the same cannot
be automatically guaranteed for the file system data itself. Ext3 is designed to take
care of both metadata and data. The degree of “care” can be customized. Enabling
Ext3 in the data=journal mode offers maximum security (data integrity), but
can slow down the system because both metadata and data are journaled. A relatively
new approach is to use the data=ordered mode, which ensures both data and
metadata integrity, but uses journaling only for metadata. The file system driver
500
collects all data blocks that correspond to one metadata update. These data blocks
are written to disk before the metadata is updated. As a result, consistency is achieved
for metadata and data without sacrificing performance. A third option to use is
data=writeback, which allows data to be written into the main file system after
its metadata has been committed to the journal. This option is often considered the
best in performance. It can, however, allow old data to reappear in files after crash
and recovery while internal file system integrity is maintained. Unless you specify
something else, Ext3 is run with the data=ordered default.
34.2.4 Converting an Ext2 File System into
Ext3
Converting from Ext2 to Ext3 involves two separate steps:
Creating the Journal
Log in as root and run tune2fs -j. This creates an Ext3 journal with the default
parameters. To decide yourself how large the journal should be and on which device
it should reside, run tune2fs -J instead together with the desired journal options
size= and device=. More information about the tune2fs program is available
in its manual page (tune2fs(8)).
Specifying the File System Type in /etc/fstab
To ensure that the Ext3 file system is recognized as such, edit the file /etc/fstab,
changing the file system type specified for the corresponding partition from ext2
to ext3. The change takes effect after the next reboot.
Using Ext3 for the Root Directory
To boot a root file system set up as an Ext3 partition, include the modules ext3
and jbd in the initrd. To do so, edit the file /etc/sysconfig/kernel to
include the two modules under INITRD_MODULES then execute the command
mkinitrd.
34.2.5 Reiser4
Right after kernel 2.6 had been released, the family of journaling file systems was joined
by another member: Reiser4. Reiser4 is fundamentally different from its predecessor
File Systems in Linux
501
ReiserFS (version 3.6). It introduces the concept of plug-ins to tweak the file system
functionality and a finer grained security concept.
Fine Grained Security Concept
In designing Reiser4, its developers put an emphasis on the implementation of security-relevant features. Reiser4 therefore comes with a set of dedicated security plugins. The most important one introduces the concept of file “items.” Currently, file
access controls are defined per file. If there is a large file containing information
relevant to several users, groups, or applications, the access rights had be fairly
imprecise to include all parties involved. In Reiser4, you can split those files into
smaller portions (the “items”). Access rights can then be set for each item and each
user separately, allowing a much more precise file security management. A perfect
example would be /etc/passwd. To date, only root can read and edit the file
while non-root users only get read access to this file. Using the item concept of
Reiser4, you could split this file in a set of items (one item per user) and allow users
or applications to modify their own data but not access other users' data. This concept
adds both to security and flexibility.
Extensibility through Plug-Ins
Many file system functions and external functions normally used by a file system
are implemented as plug-ins in Reiser4. These plug-ins can easily be added to the
base system. You no longer need to recompile the kernel or reformat the hard disk
to add new functionalities to your file system.
Better File System Layout through Delayed Allocation
Like XFS, Reiser4 supports delayed allocation. See Section 34.2.7, “XFS” (page 503).
Using delayed allocation even for metadata can result in better overall layout.
34.2.6 JFS
JFS, the Journaling File System, was developed by IBM. The first beta version of the
JFS Linux port reached the Linux community in the summer of 2000. Version 1.0.0
was released in 2001. JFS is tailored to suit the needs of high throughput server environments where performance is the ultimate goal. Being a full 64-bit file system, JFS
supports both large files and partitions, which is another reason for its use in server
environments.
A closer look at JFS shows why this file system might prove a good choice for your
Linux server:
502
Efficient Journaling
JFS follows a “metadata-only” approach. Instead of an extensive check, only
metadata changes generated by recent file system activity are checked, which saves
a great amount of time in recovery. Concurrent operations requiring multiple concurrent log entries can be combined into one group commit, greatly reducing performance loss of the file system through multiple write operations.
Efficient Directory Organization
JFS holds two different directory organizations. For small directories, it allows the
directory's content to be stored directly into its inode. For larger directories, it uses
B+trees, which greatly facilitate directory management.
Better Space Usage through Dynamic inode Allocation
For Ext2, you must define the inode density in advance (the space occupied by
management information), which restricts the maximum number of files or directories
of your file system. JFS spares you these considerations—it dynamically allocates
inode space and frees it when it is no longer needed.
34.2.7 XFS
Originally intended as the file system for their IRIX OS, SGI started XFS development
in the early 1990s. The idea behind XFS was to create a high-performance 64-bit journaling file system to meet the extreme computing challenges of today. XFS is very
good at manipulating large files and performs well on high-end hardware. However,
even XFS has a drawback. Like ReiserFS, XFS takes great care of metadata integrity,
but less of data integrity.
A quick review of XFS's key features explains why it may prove a strong competitor
for other journaling file systems in high-end computing.
High Scalability through the Use of Allocation Groups
At the creation time of an XFS file system, the block device underlying the file
system is divided into eight or more linear regions of equal size. Those are referred
to as allocation groups. Each allocation group manages its own inodes and free disk
space. Practically, allocation groups can be seen as file systems in a file system.
Because allocation groups are rather independent of each other, more than one of
them can be addressed by the kernel simultaneously. This feature is the key to XFS's
great scalability. Naturally, the concept of independent allocation groups suits the
needs of multiprocessor systems.
File Systems in Linux
503
High Performance through Efficient Management of Disk Space
Free space and inodes are handled by B+ trees inside the allocation groups. The use
of B+ trees greatly contributes to XFS's performance and scalability. XFS uses delayed allocation. It handles allocation by breaking the process into two pieces. A
pending transaction is stored in RAM and the appropriate amount of space is reserved. XFS still does not decide where exactly (speaking of file system blocks) the
data should be stored. This decision is delayed until the last possible moment. Some
short-lived temporary data may never make its way to disk, because it may be obsolete by the time XFS decides where actually to save it. Thus XFS increases write
performance and reduces file system fragmentation. Because delayed allocation
results in less frequent write events than in other file systems, it is likely that data
loss after a crash during a write is more severe.
Preallocation to Avoid File System Fragmentation
Before writing the data to the file system, XFS reserves (preallocates) the free space
needed for a file. Thus, file system fragmentation is greatly reduced. Performance
is increased because the contents of a file are not distributed all over the file system.
34.3
Some Other Supported File
Systems
Table 34.1, “File System Types in Linux” (page 504) summarizes some other file systems
supported by Linux. They are supported mainly to ensure compatibility and interchange
of data with different kinds of media or foreign operating systems.
Table 34.1
504
File System Types in Linux
cramfs
Compressed ROM file system: A compressed read-only file system for ROMs.
hpfs
High Performance File System: The IBM OS/2 standard file
system—only supported in read-only mode.
iso9660
Standard file system on CD-ROMs.
minix
This file system originated from academic projects on operating
systems and was the first file system used in Linux. Today, it is
used as a file system for floppy disks.
msdos
fat, the file system originally used by DOS, is today used by
various operating systems.
ncpfs
File system for mounting Novell volumes over networks.
nfs
Network File System: Here, data can be stored on any machine
in a network and access may be granted via a network.
smbfs
Server Message Block is used by products such as Windows to
enable file access over a network.
sysv
Used on SCO UNIX, Xenix, and Coherent (commercial UNIX
systems for PCs).
ufs
Used by BSD, SunOS, and NeXTstep. Only supported in readonly mode.
umsdos
UNIX on MSDOS: Applied on top of a normal fat file system,
achieves UNIX functionality (permissions, links, long filenames)
by creating special files.
vfat
Virtual FAT: Extension of the fat file system (supports long
filenames).
ntfs
Windows NT file system, read-only.
34.4
Large File Support in Linux
Originally, Linux supported a maximum file size of 2 GB. This was enough before the
explosion of multimedia and as long as no one tried to manipulate huge databases on
Linux. Becoming more and more important for server computing, the kernel and C library were modified to support file sizes larger than 2 GB when using a new set of interfaces that applications must use. Today, almost all major file systems offer LFS
File Systems in Linux
505
support, allowing you to perform high-end computing. Table 34.2, “Maximum Sizes
of File Systems (On-Disk Format)” (page 506) offers an overview of the current limitations of Linux files and file systems.
Table 34.2
Maximum Sizes of File Systems (On-Disk Format)
File System
File Size (Bytes)
File System Size
(Bytes)
Ext2 or Ext3 (1 kB block size)
234 (16 GB)
241 (2 TB)
Ext2 or Ext3 (2 kB block size)
238 (256 GB)
243 (8 TB)
Ext2 or Ext3 (4 kB block size)
241 (2 TB)
244 (16 TB)
Ext2 or Ext3 (8 kB block size)
(systems with 8 kB pages, like
Alpha)
246 (64 TB)
245 (32 TB)
ReiserFS v3
246 (64 GB)
245 (32 TB)
XFS
263 (8 EB)
263 (8 EB)
JFS (512 byte block size)
263 (8 EB)
249 (512 TB)
JFS (4 kB block size)
263 (8 EB)
252 (4 PB)
NFSv2 (client side)
231 (2 GB)
263 (8 EB)
NFSv3 (client side)
263 (8 EB)
263 (8 EB)
IMPORTANT: Linux Kernel Limits
Table 34.2, “Maximum Sizes of File Systems (On-Disk Format)” (page 506) describes the limitations regarding the on-disk format. The 2.6 kernel imposes its
own limits on the size of files and file systems handled by it. These are as follows:
File Size
41
On 32-bit systems, files may not exceed the size of 2 TB (2 bytes).
506
File System Size
73
File systems may be up to 2 bytes large. However, this limit is still out of
reach for the currently available hardware.
34.5
For More Information
Each of the file system projects described above maintains its own home page on which
to find mailing list information, further documentation, and FAQs.
• http://e2fsprogs.sourceforge.net/
• http://www.zipworld.com.au/~akpm/linux/ext3/
• http://www.namesys.com/
• http://oss.software.ibm.com/developerworks/opensource/
jfs/
• http://oss.sgi.com/projects/xfs/
A comprehensive multipart tutorial about Linux file systems can be found at IBM developerWorks: http://www-106.ibm.com/developerworks/library/
l-fs.html. For a comparison of the different journaling file systems in Linux, look
at Juan I. Santos Florido's article at Linuxgazette: http://www.linuxgazette
.com/issue55/florido.html. Those interested in an in-depth analysis of LFS
in Linux should try Andreas Jaeger's LFS site: http://www.suse.de/~aj/linux
_lfs.html.
File Systems in Linux
507
35
The X Window System
The X Window System (X11) is the de facto standard for graphical user interfaces in
UNIX. X is network-based, enabling applications started on one host to be displayed
on another host connected over any kind of network (LAN or Internet). This chapter
describes the setup and optimization of the X Window System environment, provides
background information about the use of fonts in SUSE Linux, and explains the configuration of OpenGL and 3D.
35.1
X11 Setup with SaX2
The graphical user interface, or X server, handles the communication between hardware
and software. Desktops, like KDE and GNOME, and the wide variety of window
managers, use the X server for interaction with the user. The graphical user interface
is initially configured during installation. To change the settings afterwards, use the
respective module from the YaST control center or run SaX2 manually from the command line with the command sax2. The SaX2 main window provides a common umbrella for the individual modules from the YaST control center.
The X Window System
509
Figure 35.1
The Main Window of SaX2
In the left navigation bar, there are six items, each of them showing the respective
configuration dialog from the YaST control center. Find the sections mentioned below
in Chapter System Configuration with YaST (↑Start-Up).
Monitor
For a description of the monitor and graphics card configuration, see Section “Card
and Monitor Properties” (Chapter 3, System Configuration with YaST, ↑Start-Up).
Mouse
For a description of the mouse configuration in the graphical environment, see
Section “Mouse Properties” (Chapter 3, System Configuration with YaST, ↑StartUp).
Keyboard
For a description of the keyboard configuration in the graphical environment, see
Section “Keyboard Properties” (Chapter 3, System Configuration with YaST, ↑StartUp).
Tablet
For a description of the graphics tablet configuration, see Section “Tablet Properties”
(Chapter 3, System Configuration with YaST, ↑Start-Up).
510
Touchscreen
For a description of the touchscreen configuration, see Section “Touchscreen
Properties” (Chapter 3, System Configuration with YaST, ↑Start-Up).
VNC
For a description of the VNC configuration, see Section “Remote Access Properties”
(Chapter 3, System Configuration with YaST, ↑Start-Up).
35.2
Optimizing the X Configuration
X.Org is an Open Source implementation of the X Window System. It is further developed by the X.Org Foundation, which is also responsible for the development of new
technologies and standards of the X Window System.
To use the available hardware, including mouse, graphics card, monitor, and keyboard,
in the best way possible, the configuration can be optimized manually. Some aspects
of this optimization are explained below. For detailed information about configuring
the X Window System, review the various files in the directory /usr/share/doc/
packages/Xorg and man xorg.conf.
WARNING
Be very careful when configuring your X Window System. Never start the X
Window System until the configuration is finished. A wrongly configured system
can cause irreparable damage to your hardware (this applies especially to fixedfrequency monitors). The authors of this book and SUSE Linux cannot be held
responsible for damage. This information has been carefully researched, but
this does not guarantee that all methods presented here are correct and will
not damage your hardware.
The programs SaX2 and xorgconfig create the file xorg.conf, by default in /etc/
X11. This is the primary configuration file for the X Window System. Find all the settings here concerning your graphics card, mouse, and monitor.
The following paragraphs describe the structure of the configuration file /etc/X11/
xorg.conf. It consists of several sections, each one dealing with a certain aspect of
the configuration. Each section starts with the keyword Section <designation>
and ends with EndSection. The sections have the form:
The X Window System
511
Section designation
entry 1
entry 2
entry n
EndSection
The available section types are listed in Table 35.1, “Sections in /etc/X11/xorg.conf”
(page 512).
Table 35.1
512
Sections in /etc/X11/xorg.conf
Type
Meaning
Files
This section describes the paths used for fonts and the RGB
color table.
ServerFlags
General switches are set here.
InputDevice
Input devices, like keyboards and special input devices (touchpads, joysticks, etc.), are configured in this section. Important
parameters in this section are Driver and the options defining
the Protocol and Device.
Monitor
Describes the monitor used. The individual elements of this
section are the name, which is referred to later in the Screen
definition, the bandwidth, and the synchronization frequency
limits (HorizSync and VertRefresh). Settings are given
in MHz, kHz, and Hz. Normally, the server refuses any modeline
that does not correspond with the specification of the monitor.
This prevents too high frequencies from being sent to the monitor
by accident.
Modes
The modeline parameters are stored here for the specific screen
resolutions. These parameters can be calculated by SaX2 on the
basis of the values given by the user and normally do not need
to be changed. Intervene manually at this point, if, for example,
you want to connect a fixed frequency monitor. Find details of
the meaning of individual number values in the HOWTO file
/usr/share/doc/howto/en/
XFree86-Video-Timings-HOWTO.gz.
Type
Meaning
Device
This section defines a specific graphics card. It is referenced by
its descriptive name.
Screen
This section puts together a Monitor and a Device to form
all the necessary settings for X.Org. In the Display subsection,
specify the size of the virtual screen (Virtual), the
ViewPort, and the Modes used with this screen.
ServerLayout This section defines the layout of a single or multihead configuration. This section binds the input devices InputDevice and
the display devices Screen.
Monitor, Device, and Screen are explained in more detail below. Further information about the other sections can be found in the manual pages of X.Org and xorg
.conf.
There can be several different Monitor and Device sections in xorg.conf. Even
multiple Screen sections are possible. The following ServerLayout section determines which one is used.
35.2.1 Screen Section
First, take a closer look at the screen section, which combines a monitor with a device
section and determines the resolution and color depth to use. A screen section might
resemble Example 35.1, “Screen Section of the File /etc/X11/xorg.conf” (page 514).
The X Window System
513
Example 35.1
Screen Section of the File /etc/X11/xorg.conf
Section "Screen"
DefaultDepth 16
SubSection "Display"
Depth
16
Modes
"1152x864" "1024x768" "800x600"
Virtual
1152x864
EndSubSection
SubSection "Display"
Depth
24
Modes
"1280x1024"
EndSubSection
SubSection "Display"
Depth
32
Modes "640x480"
EndSubSection
SubSection "Display"
Depth
8
Modes
"1280x1024"
EndSubSection
Device
"Device[0]"
Identifier
"Screen[0]"
Monitor
"Monitor[0]"
EndSection
The line Identifier (here Screen[0]) gives this section a defined name with
which it can be uniquely referenced in the following ServerLayout section. The
lines Device and Monitor specify the graphics card and the monitor that belong to
this definition. These are just links to the Device and Monitor sections with their
corresponding names or identifiers. These sections are discussed in detail below.
Use the DefaultDepth setting to select the color depth the server should use unless
it is started with a specific color depth. There is a Display subsection for each color
depth. The keyword Depth assigns the color depth valid for this subsection. Possible
values for Depth are 8, 15, 16, and 24. Not all X server modules support all these
values.
After the color depth, a list of resolutions is set in the Modes section. This list is checked
by the X server from left to right. For each resolution, the X server searches for a suitable
Modeline in the Modes section. The Modeline depends on the capability of both
the monitor and the graphics card. The Monitor settings determine the resulting
Modeline.
The first resolution found is the Default mode. With Ctrl +
pad), switch to the next resolution in the list to the right. With
514
Alt
Ctrl
+ + (on the number
+ Alt + – (on the
number pad), switch to the left. This enables you to vary the resolution while X is running.
The last line of the Display subsection with Depth 16 refers to the size of the virtual screen. The maximum possible size of a virtual screen depends on the amount of
memory installed on the graphics card and the desired color depth, not on the maximum
resolution of the monitor. Because modern graphics cards have a large amount of video
memory, you can create very large virtual desktops. However, you may no longer be
able to use 3D functionality if you fill most of the video memory with a virtual desktop.
If the card has 16 MB video RAM, for example, the virtual screen can be up to
4096x4096 pixels in size at 8-bit color depth. Especially for accelerated cards, however,
it is not recommended to use all your memory for the virtual screen, because this
memory on the card is also used for several font and graphics caches.
35.2.2 Device Section
A device section describes a specific graphics card. You can have as many device entries
in xorg.conf as you like, as long as their names are differentiated, using the keyword
Identifier. As a rule—if you have more than one graphics card installed—the
sections are simply numbered in order. The first one is called Device[0], the second
one Device[1], and so on. The following file shows an excerpt from the Device
section of a computer with a Matrox Millennium PCI graphics card:
Section "Device"
BoardName
"MGA2064W"
BusID
"0:19:0"
Driver
"mga"
Identifier
"Device[0]"
VendorName
"Matrox"
Option
"sw_cursor"
EndSection
If you use SaX2 for configuring, the device section should look something like the
above example. Both the Driver and BusID are dependent on the hardware installed
in your computer and are detected by SaX2 automatically. The BusID defines the PCI
or AGP slot in which the graphics card is installed. This matches the ID displayed by
the command lspci. The X server needs details in decimal form, but lspci displays these
in hexadecimal form.
Via the Driver parameter, specify the driver to use for this graphics card. If the card
is a Matrox Millennium, the driver module is called mga. The X server then searches
The X Window System
515
through the ModulePath defined in the Files section in the drivers subdirectory.
In a standard installation, this is the directory /usr/X11R6/lib/modules/
drivers. _drv.o is added to the name, so, in the case of the mga driver, the driver
file mga_drv.o is loaded.
The behavior of the X server or of the driver can also be influenced through additional
options. An example of this is the option sw_cursor, which is set in the device section.
This deactivates the hardware mouse cursor and depicts the mouse cursor using software.
Depending on the driver module, there are various options available, which can be
found in the description files of the driver modules in the directory /usr/X11R6/
lib/X11/doc. Generally valid options can also be found in the manual pages
(man xorg.conf and man X.Org).
35.2.3 Monitor and Modes Section
Like the Device sections, the Monitor and Modes sections describe one monitor
each. The configuration file /etc/X11/xorg.conf can contain as many Monitor
sections as desired. The server layout section specifies which Monitor section is relevant.
Monitor definitions should only be set by experienced users. The modelines constitute
an important part of the Monitor sections. Modelines set horizontal and vertical timings
for the respective resolution. The monitor properties, especially the allowed frequencies,
are stored in the Monitor section.
WARNING
Unless you have an in-depth knowledge of monitor and graphics card functions,
nothing should be changed in the modelines, because this could cause severe
damage to your monitor.
Those who try to develop their own monitor descriptions should be very familiar with
the documentation in /usr/X11/lib/X11/doc. The section covering the video
modes deserves a special mention. It describes, in detail, how the hardware functions
and how to create modelines.
Manual specification of modelines is rarely required today. If you are using a modern
multisync monitor, the allowed frequencies and optimal resolutions can, as a rule, be
read directly from the monitor by the X server via DDC, as described in the SaX2
516
configuration section. If this is not possible for some reason, use one of the VESA
modes included in the X server. This will function with practically all graphics card
and monitor combinations.
35.3
Installing and Configuring Fonts
The installation of additional fonts in SUSE Linux is very easy. Simply copy the fonts
to any directory located in the X11 font path (see Section 35.3.2, “X11 Core Fonts”
(page 521)). To enable use of the fonts, the installation directory should be a subdirectory
of the directories configured in /etc/fonts/fonts.conf (see Section 35.3.1,
“Xft” (page 517)).
The font files can be copied manually (as root) to a suitable directory, such as /usr/
X11R6/lib/X11/fonts/truetype. Alternatively, the task can be performed
with the KDE font installer in the KDE Control Center. The result is the same.
Instead of copying the actual fonts, you can also create symbolic links. For example,
you may want to do this if you have licensed fonts on a mounted Windows partition
and want to use them. Subsequently, run SuSEconfig --module fonts.
SuSEconfig --module fonts executes the script /usr/sbin/
fonts-config, which handles the configuration of the fonts. To see what this script
does, refer to the manual page of the script (man fonts-config).
The procedure is the same for bitmap fonts, TrueType and OpenType fonts, and Type1
(PostScript) fonts. All these font types can be installed in any directory. Only CIDkeyed fonts require a slightly different procedure. For this, see Section 35.3.3, “CIDKeyed Fonts” (page 522).
X.Org contains two completely different font systems: the old X11 core font system
and the newly designed Xft and fontconfig system. The following sections briefly describe these two systems.
35.3.1 Xft
From the outset, the programmers of Xft made sure that scalable fonts including antialiasing are supported well. If Xft is used, the fonts are rendered by the application
using the fonts, not by the X server as in the X11 core font system. In this way, the reThe X Window System
517
spective application has access to the actual font files and full control of how the glyphs
are rendered. This constitutes the basis for the correct display of text in a number of
languages. Direct access to the font files is very useful for embedding fonts for printing
to make sure that the printout looks the same as the screen output.
In SUSE Linux, the two desktop environments KDE and GNOME, Mozilla, and many
other applications already use Xft by default. Xft is already used by more applications
than the old X11 core font system.
Xft uses the fontconfig library for finding fonts and influencing how they are rendered.
The properties of fontconfig are controlled by the global configuration file /etc/
fonts/fonts.conf and the user-specific configuration file ~/.fonts.conf.
Each of these fontconfig configuration files must begin with
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
and end with
</fontconfig>
To add directories to search for fonts, append lines such as the following:
<dir>/usr/local/share/fonts/</dir>
However, this is usually not necessary. By default, the user-specific directory ~/.fonts
is already entered in /etc/fonts/fonts.conf. Accordingly, all you need to do
to install additional fonts is to copy them to ~/.fonts.
You can also insert rules that influence the appearance of the fonts. For example, enter
<match target="font">
<edit name="antialias" mode="assign">
<bool>false</bool>
</edit>
</match>
to disable antialiasing for all fonts or
<match target="font">
<test name="family">
<string>Luxi Mono</string>
<string>Luxi Sans</string>
</test>
<edit name="antialias" mode="assign">
<bool>false</bool>
518
</edit>
</match>
to disable antialiasing for specific fonts.
By default, most applications use the font names sans-serif (or the equivalent
sans), serif, or monospace. These are not real fonts but only aliases that are resolved to a suitable font, depending on the language setting.
Users can easily add rules to ~/.fonts.conf to resolve these aliases to their favorite
fonts:
<alias>
<family>sans-serif</family>
<prefer>
<family>FreeSans</family>
</prefer>
</alias>
<alias>
<family>serif</family>
<prefer>
<family>FreeSerif</family>
</prefer>
</alias>
<alias>
<family>monospace</family>
<prefer>
<family>FreeMono</family>
</prefer>
</alias>
Because nearly all applications use these aliases by default, this affects almost the entire
system. Thus, you can easily use your favorite fonts almost everywhere without having
to modify the font settings in the individual applications.
Use the command fc-list to find out which fonts are installed and available for use.
For instance, the command fc-list returns a list of all fonts. To find out which of
the available scalable fonts (:outline=true) contain all glyphs required for Hebrew
(:lang=he), their font names (family), their style (style), their weight (weight),
and the name of the files containing the fonts, enter the following command:
fc-list ":lang=he:outline=true" family style weight
The output of this command could appear as follows:
FreeSansBold.ttf: FreeSans:style=Bold:weight=200
FreeMonoBoldOblique.ttf: FreeMono:style=BoldOblique:weight=200
The X Window System
519
FreeSerif.ttf: FreeSerif:style=Medium:weight=80
FreeSerifBoldItalic.ttf: FreeSerif:style=BoldItalic:weight=200
FreeSansOblique.ttf: FreeSans:style=Oblique:weight=80
FreeSerifItalic.ttf: FreeSerif:style=Italic:weight=80
FreeMonoOblique.ttf: FreeMono:style=Oblique:weight=80
FreeMono.ttf: FreeMono:style=Medium:weight=80
FreeSans.ttf: FreeSans:style=Medium:weight=80
FreeSerifBold.ttf: FreeSerif:style=Bold:weight=200
FreeSansBoldOblique.ttf: FreeSans:style=BoldOblique:weight=200
FreeMonoBold.ttf: FreeMono:style=Bold:weight=200
Important parameters that can be queried with fc-list:
Table 35.2
520
Parameters of fc-list
Parameter
Meaning and Possible Values
family
Name of the font family, for example, FreeSans.
foundry
The manufacturer of the font, for example, urw.
style
The font style, such as Medium, Regular, Bold,
Italic, Heavy.
lang
The language that the font supports, for example, de for
German, ja for Japanese, zh-TW for traditional Chinese,
or zh-CN for simplified Chinese.
weight
The font weight, such as 80 for regular, 200 for bold.
slant
The slant, usually 0 for none and 100 for italic.
file
The name of the file containing the font.
outline
true for outline fonts, false for other fonts.
scalable
true for scalable fonts, false for other fonts.
bitmap
true for bitmap fonts, false for other fonts.
pixelsize
Font size in pixels. In connection with fc-list, this option
only makes sense for bitmap fonts.
35.3.2 X11 Core Fonts
Today, the X11 core font system supports not only bitmap fonts but also scalable fonts,
like Type1 fonts, TrueType and OpenType fonts, and CID-keyed fonts. Unicode fonts
have also been supported for quite some time. In 1987, the X11 core font system was
originally developed for X11R1 for the purpose of processing monochrome bitmap
fonts. All extensions mentioned above were added later.
Scalable fonts are only supported without antialiasing and subpixel rendering and the
loading of large scalable fonts with glyphs for many languages may take a long time.
The use of Unicode fonts may also be slow and requires more memory.
The X11 core font system has a few inherent weaknesses. It is outdated and can no
longer be extended in a meaningful fashion. Although it must be retained for reasons
of backward compatibility, the more modern Xft and fontconfig system should be used
if at all possible.
For its operation, the X server needs to know what fonts it has available and where in
the system it can find them. This is handled by a FontPath variable, which contains the
path to all valid system font directories. In each of these directories, a file named fonts
.dir lists the available fonts in this directory. The FontPath is generated by the X
server at start-up. It searches for a valid fonts.dir file in each of the FontPath
entries in the configuration file /etc/X11/xorg.conf. These entries are found in
the Files section. Display the actual FontPath with xset q. This path may also be
changed at runtime with xset. To add an additional path, use xset +fp <path>. To
remove an unwanted path, use xset -fp <path>.
If the X server is already active, newly installed fonts in mounted directories can be
made available with the command xset fp rehash. This command is executed by
SuSEconfig --module fonts. Because the command xset needs access to the
running X server, this only works if SuSEconfig --module fonts is started from
a shell that has access to the running X server. The easiest way to achieve this is to assume root permissions by entering su and the root password. su transfers the access
permissions of the user who started the X server to the root shell. To check if the fonts
were installed correctly and are available by way of the X11 core font system, use the
command xlsfonts to list all available fonts.
By default, SUSE Linux uses UTF-8 locales. Therefore, Unicode fonts should be preferred (font names ending with iso10646-1 in xlsfonts output). All available
The X Window System
521
Unicode fonts can be listed with xlsfonts | grep iso10646-1. Nearly all
Unicode fonts available in SUSE Linux contain at least the glyphs needed for European
languages (formerly encoded as iso-8859-*).
35.3.3 CID-Keyed Fonts
In contrast to the other font types, you cannot simply install CID-keyed fonts in just
any directory. CID-keyed fonts must be installed in /usr/share/ghostscript/
Resource/CIDFont. This is not relevant for Xft and fontconfig, but it is necessary
for Ghostscript and the X11 core font system.
TIP
See http://www.xfree86.org/current/fonts.html for more information about fonts under X11.
35.4
OpenGL—3D Configuration
35.4.1 Hardware Support
SUSE Linux includes several OpenGL drivers for 3D hardware support. Table 35.3,
“Supported 3D Hardware” (page 522) provides an overview.
Table 35.3
Supported 3D Hardware
OpenGL Driver
Supported Hardware
nVidia
nVidia Chips: all except Riva 128(ZX)
DRI
3Dfx Voodoo Banshee,
3Dfx Voodoo-3/4/5,
Intel i810/i815/i830M,
Intel 845G/852GM/855GM/865G/915,
522
OpenGL Driver
Supported Hardware
Matrox G200/G400/G450/G550,
ATI Rage 128(Pro)/Radeon (up to 9250)
If you are installing with YaST for the first time, 3D acceleration can be activated during
installation, provided YaST detects 3D support. For nVidia graphics chips, the nVidia
driver must be installed first. To do this, select the nVidia driver patch in YOU (YaST
Online Update). Due to license restrictions, the nVidia driver is not included in the
distribution.
If an update is carried out instead of a new installation or a 3Dfx add-on graphics adapter
(Voodoo Graphics or Voodoo-2) needs to be set up, the procedure for configuring 3D
hardware support is different. This depends on which OpenGL driver is used. Further
details are provided in the following section.
35.4.2 OpenGL Drivers
The OpenGL drivers nVidia and DRI can be configured easily with SaX2. For nVidia
adapters, the nVidia driver must be installed first. Enter the command 3Ddiag to check
if the configuration for nVidia or DRI is correct.
For security reasons, only users belonging to the group video are permitted to access
the 3D hardware. Therefore, make sure that all local users are members of this group.
Otherwise, the slow software rendering fallback of the OpenGL driver is used for
OpenGL applications. Use the command id to check whether the current user belongs
to the group video. If this is not the case, use YaST to add the user to the group.
35.4.3 The Diagnosis Tool 3Ddiag
The diagnosis tool 3Ddiag allows verification of the 3D configuration in SUSE Linux.
This is a command line tool that must be started in a terminal. Enter 3Ddiag -h to
list possible options for 3Ddiag.
To verify the X.Org configuration, the tool checks if the packages needed for 3D support
are installed and if the correct OpenGL library and GLX extension are used. Follow
The X Window System
523
the instructions of 3Ddiag if you receive failed messages. If everything is correct, you
only see done messages on the screen.
35.4.4 OpenGL Test Utilities
For testing OpenGL, the program glxgears and games like tuxracer and
armagetron (packages have the same names) can be useful. If 3D support has been
activated, it should be possible to play these smoothly on a fairly new computer.
Without 3D support, these games would run very slowly (slideshow effect). Use the
glxinfo command to verify that 3D is active, in which case the output contains a
line with direct rendering: Yes.
35.4.5 Troubleshooting
If the OpenGL 3D test results are negative (the games cannot be smoothly played), use
3Ddiag to make sure no errors exist in the configuration (failed messages). If correcting
these does not help or if failed messages have not appeared, take a look at the X.Org
log files.
Often, you will find the line DRI is disabled in the X.Org file /var/log/Xorg
.0.log. The exact cause can only be discovered by closely examining the log file—a
task requiring some experience.
In such cases, no configuration error exists, because this would have already been detected by 3Ddiag. Consequently, at this point, the only choice is to use the software
rendering fallback of the DRI driver, which does not provide 3D hardware support.
You should also go without 3D support if you get OpenGL representation errors or instability. Use SaX2 to disable 3D support completely.
35.4.6 Installation Support
Apart from the software rendering fallback of the DRI driver, all OpenGL
drivers in Linux are in developmental phases and are therefore considered experimental.
The drivers are included in the distribution because of the high demand for 3D hardware
acceleration in Linux. Considering the experimental status of OpenGL drivers, SUSE
cannot offer any installation support for configuring 3D hardware acceleration or provide
any further assistance with related problems. The basic configuration of the graphical
524
user interface (X Window System) does not include 3D hardware acceleration configuration. If you experience problems with 3D hardware acceleration, it is recommended
to disable 3D support completely.
35.4.7 Additional Online Documentation
For information about DRI, refer to /usr/X11R6/lib/X11/doc/README.DRI
(xorg-x11-doc). More information about nvidia driver installation is found at
http://ftp.suse.com/pub/suse/i386/supplementary/X/
nvidia-installer-HOWTO.html.
The X Window System
525
36
Authentication with PAM
Linux uses PAM (Pluggable Authentication Modules) in the authentication process as
a layer that mediates between user and application. PAM modules are available on a
systemwide basis, so they can be requested by any application. This chapter describes
how the modular authentication mechanism works and how it is configured.
System administrators and programmers often want to restrict access to certain parts
of the system or to limit the use of certain functions of an application. Without PAM,
applications must be adapted every time a new authentication mechanism, such as
LDAP or SAMBA, is introduced. This process, however, is rather time-consuming and
error-prone. One way to avoid these drawbacks is to separate applications from the
authentication mechanism and to delegate the latter to centrally managed modules.
Whenever a newly required authentication scheme is needed, it is sufficient to adapt
or write a suitable PAM module for use by the program in question.
Every program that relies on the PAM mechanism has its own configuration file in the
directory /etc/pam.d/programname. These files define the PAM modules used
for authentication. In addition, there are global configuration files for most PAM
modules under /etc/security, which define the exact behavior of these modules
(examples include pam_env.conf, pam_pwcheck.conf, pam_unix2.conf,
and time.conf). Every application that uses a PAM module actually calls a set of
PAM functions, which then process the information in the various configuration files
and return the result to the calling application.
Authentication with PAM
527
36.1
Structure of a PAM
Configuration File
Each line in a PAM configuration file contains a maximum of four columns:
<Type of module> <Control flag> <Module path> <Options>
PAM modules are processed as stacks. Different types of modules have different purposes, for example, one module checks the password, another one verifies the location
from which the system is accessed, and yet another one reads user-specific settings.
PAM knows about four different types of modules:
auth
The purpose of this type of module is to check the user's authenticity. This is traditionally done by querying a password, but it can also be achieved with the help of
a chip card or through biometrics (fingerprints or iris scan).
account
Modules of this type check whether the user has general permission to use the requested service. As an example, such a check should be performed to ensure that
no one can log in under the username of an expired account.
password
The purpose of this type of module is to enable the change of an authentication token.
In most cases, this is a password.
session
Modules of this type are responsible for managing and configuring user sessions.
They are started before and after authentication to register login attempts in system
logs and to configure the user's specific environment (mail accounts, home directory,
system limits, etc.).
The second column contains control flags to influence the behavior of the modules
started:
required
A module with this flag must be successfully processed before the authentication
may proceed. After the failure of a module with the required flag, all other
528
modules with the same flag are processed before the user receives a message about
the failure of the authentication attempt.
requisite
Modules having this flag must also be processed successfully, in much the same
way as a module with the required flag. However, in case of failure a module
with this flag gives immediate feedback to the user and no further modules are
processed. In case of success, other modules are subsequently processed, just like
any modules with the required flag. The requisite flag can be used as a basic
filter checking for the existence of certain conditions that are essential for a correct
authentication.
sufficient
After a module with this flag has been successfully processed, the calling application
receives an immediate message about the success and no further modules are processed, provided there was no preceding failure of a module with the required
flag. The failure of a module with the sufficient flag has no direct consequences,
in the sense that any subsequent modules are processed in their respective order.
optional
The failure or success of a module with this flag does not have any direct consequences. This can be useful for modules that are only intended to display a message
(for example, to tell the user that mail has arrived) without taking any further action.
include
If this flag is given, the file specified as argument is inserted at this place.
The module path does not need to be specified explicitly, as long as the module is located in the default directory /lib/security (for all 64-bit platforms supported by
SUSE Linux, the directory is /lib64/security). The fourth column may contain
an option for the given module, such as debug (enables debugging) or nullok (allows
the use of empty passwords).
36.2
The PAM Configuration of sshd
To show how the theory behind PAM works, consider the PAM configuration of sshd
as a practical example:
Authentication with PAM
529
Example 36.1
PAM Configuration for sshd
#%PAM-1.0
auth
include
common-auth
auth
required
pam_nologin.so
account include
common-account
password include
common-password
session include
common-session
# Enable the following line to get resmgr support for
# ssh sessions (see /usr/share/doc/packages/resmgr/README.SuSE)
#session optional
pam_resmgr.so fake_ttyname
The typical PAM configuration of an application (sshd, in this case) contains four include
statements referring to the configuration files of four module types: common-auth,
common-account, common-password, and common-session. These four
files hold the default configuration for each module type. By including them instead of
calling each module separately for each PAM application, automatically get an updated
PAM configuration if the administrator changes the defaults. In former times, you had
to adjust all configuration files manually for all applications when changes to PAM
occured or a new application was installed. Now the PAM configuration is made with
central configuration files and all changes are automatically inherited by the PAM
configuration of each service.
The first include file (common-auth) calls two modules of the auth type: pam_env
and pam_unix2. See Example 36.2, “Default Configuration for the auth Section”
(page 530).
Example 36.2
auth
auth
required
required
Default Configuration for the auth Section
pam_env.so
pam_unix2.so
The first one, pam_env, loads the file /etc/security/pam_env.conf to set
the environment variables as specified in this file. This can be used to set the DISPLAY
variable to the correct value, because the pam_env module knows about the location
from which the login is taking place. The second one, pam_unix2, checks the user's
login and password against /etc/passwd and /etc/shadow.
After the modules specified in common-auth have been successfully called, a third
module called pam_nologin checks whether the file /etc/nologin exists. If it
does, no user other than root may log in. The whole stack of auth modules is processed before sshd gets any feedback about whether the login has succeeded. Given
that all modules of the stack have the required control flag, they must all be processed
successfully before sshd receives a message about the positive result. If one of the
530
modules is not successful, the entire module stack is still processed and only then is
sshd notified about the negative result.
As soon as all modules of the auth type have been successfully processed, another
include statement is processed, in this case, that in Example 36.3, “Default Configuration
for the account Section” (page 531). common-account contains just one module,
pam_unix2. If pam_unix2 returns the result that the user exists, sshd receives a
message announcing this success and the next stack of modules (password) is processed, shown in Example 36.4, “Default Configuration for the password Section”
(page 531).
Example 36.3
Default Configuration for the account Section
account required
Example 36.4
pam_unix2.so
Default Configuration for the password Section
password required
password required
#password required
pam_pwcheck.so
pam_unix2.so
pam_make.so
nullok
nullok use_first_pass use_authtok
/var/yp
Again, the PAM configuration of sshd involves just an include statement referring to
the default configuration for password modules located in common-password.
These modules must successfully be completed (control flag required) whenever
the application requests the change of an authentication token. Changing a password
or another authentication token requires a security check. This is achieved with the pam
_pwcheck module. The pam_unix2 module used afterwards carries over any old
and new passwords from pam_pwcheck, so the user does not need to authenticate
again. This also makes it impossible to circumvent the checks carried out by pam
_pwcheck. The modules of the password type should be used wherever the preceding
modules of the account or the auth type are configured to complain about an expired
password.
Example 36.5
session required
session required
Default Configuration for the session Section
pam_limits.so
pam_unix2.so
As the final step, the modules of the session type, bundled in the common-session
file are called to configure the session according to the settings for the user in question.
Although pam_unix2 is processed again, it has no practical consequences due to its
none option specified in the respective configuration file of this module, pam_unix2
.conf. The pam_limits module loads the file /etc/security/limits.conf,
Authentication with PAM
531
which may define limits on the use of certain system resources. The session modules
are called a second time when user logs out.
36.3
Configuration of PAM Modules
Some of the PAM modules are configurable. The corresponding configuration files are
located in /etc/security. This section briefly describes the configuration files
relevant to the sshd example—pam_unix2.conf, pam_env.conf, pam_pwcheck
.conf, and limits.conf.
36.3.1 pam_unix2.conf
The traditional password-based authentication method is controlled by the PAM module
pam_unix2. It can read the necessary data from /etc/passwd, /etc/shadow,
NIS maps, NIS+ tables, or from an LDAP database. The behavior of this module can
be influenced by configuring the PAM options of the individual application itself or
globally by editing /etc/security/pam_unix2.conf. A very basic configuration
file for the module is shown in Example 36.6, “pam_unix2.conf” (page 532).
Example 36.6
pam_unix2.conf
auth:
nullok
account:
password:
session:
nullok
none
The nullok option for module types auth and password specifies that empty
passwords are permitted for the corresponding type of account. Users are also allowed
to change passwords for their accounts. The none option for the module type session
specifies that no messages are logged on its behalf (this is the default). Learn about
additional configuration options from the comments in the file itself and from the
manual page pam_unix2(8).
36.3.2 pam_env.conf
This file can be used to define a standardized environment for users that is set whenever
the pam_env module is called. With it, preset environment variables using the following
syntax:
532
VARIABLE
[DEFAULT=[value]]
[OVERRIDE=[value]]
VARIABLE
Name of the environment variable to set.
[DEFAULT=[value]]
Default value the administrator wants set.
[OVERRIDE=[value]]
Values that may be queried and set by pam_env, overriding the default value.
A typical example of how pam_env can be used is the adaptation of the DISPLAY
variable, which is changed whenever a remote login takes place. This is shown in Example 36.7, “pam_env.conf” (page 533).
Example 36.7
REMOTEHOST
DISPLAY
pam_env.conf
DEFAULT=localhost [email protected]{PAM_RHOST}
DEFAULT=${REMOTEHOST}:0.0 OVERRIDE=${DISPLAY}
The first line sets the value of the REMOTEHOST variable to localhost, which is
used whenever pam_env cannot determine any other value. The DISPLAY variable
in turn contains the value of REMOTEHOST. Find more information in the comments
in the file /etc/security/pam_env.conf.
36.3.3 pam_pwcheck.conf
This configuration file is for the pam_pwcheck module, which reads options from it
for all password type modules. Settings stored in this file take precedence over the
PAM settings of an individual application. If application-specific settings have not been
defined, the application uses the global settings. Example 36.8, “pam_pwcheck.conf”
(page 533) tells pam_pwcheck to allow empty passwords and modification of passwords. More options for the module are mentioned in the file /etc/security/pam
_pwcheck.conf.
Example 36.8
password:
pam_pwcheck.conf
nullok
Authentication with PAM
533
36.3.4 limits.conf
System limits can be set on a user or group basis in the file limits.conf, which is
read by the pam_limits module. The file allows you to set hard limits, which may
not be exceeded at all, and soft limits, which may be exceeded temporarily. To learn
about the syntax and the available options, read the comments included in the file.
36.4
For More Information
In the directory /usr/share/doc/packages/pam of your installed system, find
the following additional documentation:
READMEs
In the top level of this directory, there are some general README files. The subdirectory modules holds README files about the available PAM modules.
The Linux-PAM System Administrators' Guide
This document includes everything that a system administrator should know about
PAM. It discusses a range of topics, from the syntax of configuration files to the
security aspects of PAM. The document is available as a PDF file, in HTML format,
and as plain text.
The Linux-PAM Module Writers' Manual
This document summarizes the topic from the developer's point of view, with information about how to write standard-compliant PAM modules. It is available as a
PDF file, in HTML format, and as plain text.
The Linux-PAM Application Developers' Guide
This document includes everything needed by an application developer who wants
to use the PAM libraries. It is available as a PDF file, in HTML format, and as plain
text.
Thorsten Kukuk has developed a number of PAM modules for SUSE Linux and made
some information available about them at http://www.suse.de/~kukuk/pam/
.
534
Virtualization with Xen
37
Xen makes it possible to run several Linux systems on one physical machine. The
hardware for the different systems is provided virtually. This chapter gives an overview
of the possibilities and limitations of this technology. Sections about installing, configuring, and running Xen complete this introduction.
Virtual machines commonly need to emulate the hardware a system needs. The disadvantage is that the emulated hardware is much slower than the real silicon. Xen has a
different approach. It restricts emulation to as few parts as possible. To achieve this,
Xen uses paravirtualization. This is a technique that presents virtual machines similarly,
but not identically to the underlying hardware. Therefore, host and guest operating
systems are adapted on kernel level. The user space remains unchanged. Xen controls
the hardware with a hypervisor and a controlling guest, also called domain-0. These
provide all needed virtualized block and network devices. The guest systems use these
virtual block and network devices to run the system and connect to other guests or the
local network. When several physical machines running Xen are configured in a way
that the virtual block and network devices are available, it is also possible to migrate a
guest system from one piece of hardware to another while running. Originally, Xen
was developed to run up to 100 guest systems on one computer, but this number depends
strongly on the system requirements of the running guest systems, especially the
memory consumption.
To limit the CPU utilization, the Xen hypervisor offers three different schedulers. The
scheduler also may be changed while running the guest system, making it is possible
to change the priority of the running guest system. On a higher level, migrating a guest
may also be used to adjust the available CPU power.
Virtualization with Xen
535
The Xen virtualization system also has some drawbacks regarding the supported hardware:
• Several closed source drivers, such as those from Nvidia or ATI, do not work as
expected. In these cases, you must use the open source drivers if available, even if
they do not support the full capabilities of the chips. Also several WLAN chips and
cardbus bridges are not supported when using Xen.
• In version 2, Xen does not support PAE (physical address extension), whіch means
that it does not support more than 4 GB of memory.
• There is no support for ACPI. Power management and other modes that depend on
ACPI do not work.
Figure 37.1
Xen Overview
Management
Application
Management
Host OS
userspace
applications
Service
Guest OS
Service
Guest OS
userspace
applications
userspace
applications
Linux Kernel
Linux Kernel
NetWare Kernel
(paravirtualized)
(paravirtualized)
(paravirtualized)
Physical
Device
Drivers
IO
IO
Xen
virt.
Console
CPU
virt.
CPU
virt.
Memory
virt.
Network
Memory
Physical Hardware (CPU, Memory, Network, Block Devices)
536
virt.
Blockdev
37.1
Xen Installation
The installation procedure of Xen involves the setup of a domain-0 domain and the installation of Xen clients. First, make sure that the needed packages are installed. These
are python, bridge-utils, xen, and a kernel-xen package. When using SUSE
packages, Xen is added to the GRUB configuration. For other cases, make an entry in
boot/grub/menu.lst. This entry should be similar to the following:
title Xen2
kernel (hd0,0)/boot/xen.gz dom0_mem=458752
module (hd0,0)/boot/vmlinuz-xen <parameters>
module (hd0,0)/boot/initrd-xen
Replace (hd0,0) with the partition that holds your /boot directory. See also Chapter 29,
The Boot Loader (page 427). Alter the amount of dom0_mem to match your system.
The maximum value is your system memory in kB minus 65536. Replace <parameters>
with the parameters normally used to boot a Linux kernel. Then reboot into Xen mode.
This boots the Xen hypervisor and a slightly changed Linux kernel as Domain-0 that
runs most of the hardware. Apart from the exceptions already mentioned, everything
should work as normal.
37.2
Domain Installation
The installation and setup of a guest domain involves several procedures. In the following, a first guest domain is installed and all the different tasks to create a first network
connection are completed.
To install a guest system, you must provide a root file system in a block device or in a
file system image, which needs to be set up. To access this system later, use an emulated
console or set up the network connection for this guest. The installation of SUSE Linux
into a directory is supported by YaST. The hardware requirements of such a guest are
similar to a normal Linux installation.
Domains can share file systems that are mounted read-only from all domains, such as
/usr or /opt. Never share a file system that is mounted read-write. For sharing
writable data among several guest domains, use NFS or other networked or cluster file
systems.
Virtualization with Xen
537
WARNING: Starting a Guest Domain
When you start a guest domain, make sure that the file systems of the guest
are not mounted anymore by an installer or by the controlling domain-0.
The first thing to do is to create a file system image in which the Linux for the guest
is installed:
1 To create an empty image named guest1 in the directory /var/tmp/ that is
4 GB size, use the following command:
dd if=/dev/zero of=/var/tmp/guest1 seek=1M bs=4096 count=1
2 The image is just a big empty file without any information in it. To be able to
write files into it, a file system is needed:
mkreiserfs -f /var/tmp/guest1
The command mkreiserfs informs you that this is not a block special device
and asks for a confirmation. Enter Y then Enter to continue.
3 The actual installation is made in a directory. Therefore the file system image
/var/tmp/guest1 must be mounted to a directory:
mkdir -p /var/tmp/dirinstall
mount -o loop /var/tmp/guest1 /var/tmp/dirinstall
IMPORTANT
When you are finished with the installation, unmount this file system image
again. YaST also mounts the /proc file system when installing, which must be
unmounted as well:
umount /var/tmp/dirinstall/proc
umount /var/tmp/dirinstall
37.2.1 Using YaST to Install a Guest Domain
To install a guest domain with YaST, you need the previously prepared the file system
image for the new guest. Start YaST and select Software → Installation into Directory
for XEN.
538
The YaST module for directory installation has several options that should be set according your needs:
• Target Directory: /var/tmp/dirinstall
Set this option to the mount point of the file system image to use. The default is
usually acceptable.
• Run YaST and SuSEconfig at First Boot: Yes
Set this option to Yes. You will be asked for a root password and a first user when
starting the guest for the first time.
• Create Image: No
The image this creates is just a tar archive of the installation directory. This is not
useful here.
• Software
Select the type of installation to use. Any of the defaults should be a good start.
Click Next to start the installation. Depending on the number of packages, the installation
takes a while. After the installation has finished, the tls libraries must be moved away:
mv /var/tmp/dirinstall/lib/tls /var/tmp/dirinstall/lib/tls.disabled
Xen uses one of the kernels that are installed in domain-0 to start the guest domain. To
be able to use networking in the guest, the modules of this kernel must be available for
the guest as well.
cp -a /lib/modules/$(rpm -qf --qf %{VERSION}-%{RELEASE}-xen \
/boot/vmlinuz-xen) /var/tmp/dirinstall/lib/modules
To prevent file system errors, the file system image must to be unmounted after the
installation:
umount /var/tmp/dirinstall/proc
umount /var/tmp/dirinstall/
It would be possible to build specialized kernels for domain-0 on one hand and for the
guest systems on the other hand. The main difference are the hardware drivers that are
unneeded in guest systems. Because these drivers are modular and not used in the guest
systems, SUSE delivers only one kernel for both tasks.
Virtualization with Xen
539
37.2.2 Setting Up a Rescue System to Work
as a Guest Domain
The easiest way to get a running system quickly is to reuse an existing root file system,
such as the rescue system of SUSE Linux. Basically, exchange the kernel image and
the device drivers of the virtual block and network devices in this image. To make this
task easier, the script mk-xen-rescue-img.sh is available in /usr/share/
doc/packages/xen/.
The disadvantage of using the rescue method of constructing a root file system is that
the result does not have an RPM database, so you cannot easily add packages using
RPM. On the positive side, the result is relatively small but has most of what is needed
to get started with networking.
To run the script mk-xen-rescue-img.sh, you need at least the directory with the
rescue image and a destination location for the resulting image. By default, the directory
resides on the boot DVD in the directory /boot.
cd /usr/share/doc/packages/xen
./mk-xen-rescue-img.sh /media/dvd/boot /usr/local/xen 64
The first parameter of the script is the directory of the rescue image. The second parameter is the destination of the image file. Optional parameters are the disk space requirements of the newly generated guest domain and the kernel version to use.
The script then copies the image to the new location, replaces the kernel and several
kernel modules, and disables the tls directory in the system. As a last step, it generates
a configuration file for the new image in /etc/xen/.
37.3
Configuring a Xen Guest
Domain
The documentation about how to configure a guest domain is not very exhaustive. The
most information about how to configure such a domain can be found in the example
configuration file /etc/xen/config. The needed options are explained together
with a default value or at least an example configuration. For the installation described
540
in Section 37.2.1, “Using YaST to Install a Guest Domain” (page 538), create a file
/etc/xen/guest1 with the following content:
kernel = "/boot/vmlinuz-xen"
❶
ramdisk = "/boot/initrd-xen"
❷
memory = 128
❸
name = "guest1"
❹
nics = "1"
❺
vif = [ 'mac=aa:cc:00:00:00:ab, bridge=xen-br0' ] ❻
disk = [ 'file:/var/tmp/guest1,hda1,w' ] ❼
root = "/dev/hda1 ro"
❽
extra = "3"
❾
❶
Enter the path to the Xen kernel in domain-0. This kernel will run in the guest
system later.
❷
Select the appropriate initial RAM disk that contains the device drivers for the
Xen kernel. Without this, the kernel typically panics because it is unable to mount
its root file system.
❸
Define how much memory the guest domain should be given. This fails if the
system does not have enough memory available for its guests.
❹
The name for this guest.
❺
The number of virtual network interfaces for the guest domain.
❻
The configuration of the virtual network interface, including its MAC address and
the bridge to which it is connected.
❼
Set the available virtual block devices for the Xen guest. To use real block devices,
create entries like ['phy:sdb1,hda1,w',
'phy:system/swap1,hda2,w'].
❽
Sets the root device for the kernel. This must be the virtual device as seen by the
guest.
❾
Add extra kernel parameters here. The example 3 means that the guest is started
in runlevel 3.
Virtualization with Xen
541
37.4
Starting and Controlling Xen
Domains
Before the guest domain may be started, the Xen hypervisor must have enough free
memory for the new guest. First, check the amount of memory used:
xm list
Name
Domain-0
Id
0
Mem(MB)
458
CPU
0
State
r----
Time(s)
181.8
Console
If this is a computer with 512 MB, the Xen hypervisor takes away 64 MB and Domain0 occupies the rest. To free some of the memory for the new guest, the command xm
balloon is used. To set the size of Domain-0 to 330 MB, enter the following as root:
xm balloon 0 330
In the next xm list, the memory usage of Domain-0 should have dropped to 330
MB. Now there is enough memory available to start a guest with 128 MB. The command
xm start guest1 -c starts the guest and links the console of the starting guest
to the current terminal. If this is the first time that this guest starts, finish the installation
with YaST.
It is always possible to detach this console or reattach it from another terminal. To detach,
use Ctrl + ] . To reattach, first check the ID of the needed guest with xm list and
attach to that ID with xm console ID.
The xm tool of Xen has many possible parameters. View a list with a short explanation
by entering xm help. Table 37.1, “xm Commands” (page 542) provides some of the
most important commands as a starting point.
Table 37.1
542
xm Commands
xm help
Print a list of commands that are available for the xm
tool.
xm console ID
Connect to the first console (tty1) of the guest with ID
ID.
xm balloon ID Mem
Set the memory size of the domain with ID ID to Mem
in MB.
xm create domname
[-c]
Start the domain with configuration file domname. The
optional -c links the current terminal to the first tty of
the new guest.
xm shutdown ID
Do a normal shutdown of the guest with ID ID.
xm destroy ID
Terminate the guest with ID ID immediately.
xm list
Print a list of all running domains with their respective
ID, memory, and CPU time values.
xm info
Display information about the Xen host, including CPU
and memory information.
37.5
For More Information
More information about Xen can be found on the following Web sites:
• file:/usr/share/doc/packages/xen/user/html/index
.html—Official information for Xen users. It requires the package
xen-doc-html.
• file:/usr/share/doc/packages/xen/interface/html/index
.html—Some more technical interface documentation. It also requires the package
xen-doc-html.
• http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index
.html—Xen home page with many different documentation links.
• http://lists.xensource.com/—Several mailing lists about Xen.
Virtualization with Xen
543
Part IX Services
38
Basic Networking
Linux offers the necessary networking tools and features for integration into all types
of network structures. The customary Linux protocol, TCP/IP, has various services and
special features, which are discussed here. Network access using a network card, modem,
or other device can be configured with YaST. Manual configuration is also possible.
Only the fundamental mechanisms and the relevant network configuration files are
discussed in this chapter.
Linux and other Unix operating systems use the TCP/IP protocol. It is not a single
network protocol, but a family of network protocols that offer various services. The
protocols listed in Table 38.1, “Several Protocols in the TCP/IP Protocol Family”
(page 547) are provided for the purpose of exchanging data between two machines via
TCP/IP. Networks combined by TCP/IP, comprising a worldwide network are also referred to, in their entirety, as “the Internet.”
RFC stands for Request for Comments. RFCs are documents that describe various Internet protocols and implementation procedures for the operating system and its applications. The RFC documents describe the setup of Internet protocols. To expand your
knowledge about any of the protocols, refer to the appropriate RFC documents. They
are available online at http://www.ietf.org/rfc.html.
Table 38.1
Several Protocols in the TCP/IP Protocol Family
Protocol
Description
TCP
Transmission Control Protocol: A connection-oriented secure protocol.
The data to transmit is first sent by the application as a stream of data
Basic Networking
547
Protocol
Description
then converted by the operating system to the appropriate format. The
data arrives at the respective application on the destination host in the
original data stream format in which it was initially sent. TCP determines whether any data has been lost during the transmission and that
there is no mix-up. TCP is implemented wherever the data sequence
matters.
UDP
User Datagram Protocol: A connectionless, insecure protocol. The data
to transmit is sent in the form of packets generated by the application.
The order in which the data arrives at the recipient is not guaranteed
and data loss is a possibility. UDP is suitable for record-oriented applications. It features a smaller latency period than TCP.
ICMP
Internet Control Message Protocol: Essentially, this is not a protocol
for the end user, but a special control protocol that issues error reports
and can control the behavior of machines participating in TCP/IP data
transfer. In addition, it provides a special echo mode that can be viewed
using the program ping.
IGMP
Internet Group Management Protocol: This protocol controls machine
behavior when implementing IP multicast.
As shown in Figure 38.1, “Simplified Layer Model for TCP/IP” (page 549), data exchange takes place in different layers. The actual network layer is the insecure data
transfer via IP (Internet protocol). On top of IP, TCP (transmission control protocol)
guarantees, to a certain extent, security of the data transfer. The IP layer is supported
by the underlying hardware-dependent protocol, such as ethernet.
548
Figure 38.1
Simplified Layer Model for TCP/IP
Host sun
Host earth
Application Layer
Applications
Application Layer
Transport Layer
TCP, UDP
Transport Layer
Network Layer
IP
Network Layer
Data Link Layer
Ethernet, FDDI, ISDN
Data Link Layer
Physical Layer
Cable, Fiberglass
Physical Layer
Data Transfer
The diagram provides one or two examples for each layer. The layers are ordered according to abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however, is almost a complete abstraction from the hardware. Every layer
has its own special function. The special functions of each layer are mostly implicit in
their description. The data link and physical layers represent the physical network used,
such as ethernet.
Almost all hardware protocols work on a packet-oriented basis. The data to transmit is
packaged in packets, because it cannot be sent all at once. The maximum size of a
TCP/IP packet is approximately 64 KB. Packets are normally quite a bit smaller, because
the network hardware can be a limiting factor. The maximum size of a data packet on
an ethernet is about fifteen hundred bytes. The size of a TCP/IP packet is limited to this
amount when the data is sent over an ethernet. If more data is transferred, more data
packets need to be sent by the operating system.
For the layers to serve their designated functions, additional information regarding each
layer must be saved in the data packet. This takes place in the header of the packet.
Every layer attaches a small block of data, called the protocol header, to the front of
each emerging packet. A sample TCP/IP data packet traveling over an ethernet cable
is illustrated in Figure 38.2, “TCP/IP Ethernet Packet” (page 550). The proof sum is
Basic Networking
549
located at the end of the packet, not at the beginning. This simplifies things for the
network hardware.
Figure 38.2
TCP/IP Ethernet Packet
Usage Data (maximum 1460 bytes)
TCP (Layer 4) Protocol Header (approx. 20 bytes)
IP (Layer 3) Protocol Header (approx. 20 bytes)
Ethernet (Layer 2) Protocol Header (approx. 14 bytes) + Checksum (2 bytes)
When an application sends data over the network, the data passes through each layer,
all implemented in the Linux kernel except the physical layer. Each layer is responsible
for preparing the data so it can be passed to the next layer. The lowest layer is ultimately
responsible for sending the data. The entire procedure is reversed when data is received.
Like the layers of an onion, in each layer the protocol headers are removed from the
transported data. Finally, the transport layer is responsible for making the data available
for use by the applications at the destination. In this manner, one layer only communicates with the layer directly above or below it. For applications, it is irrelevant whether
data is transmitted via a 100 MBit/s FDDI network or via a 56-kbit/s modem line.
Likewise, it is irrelevant for the data line which kind of data is transmitted, as long as
packets are in the correct format.
38.1
IP Addresses and Routing
The discussion in this section is limited to IPv4 networks. For information about IPv6
protocol, the successor to IPv4, refer to Section 38.2, “IPv6—The Next Generation
Internet” (page 553).
550
38.1.1 IP Addresses
Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes)
are normally written as illustrated in the second row in Example 38.1, “Writing IP
Addresses” (page 551).
Example 38.1
Writing IP Addresses
IP Address (binary): 11000000 10101000 00000000 00010100
IP Address (decimal):
192.
168.
0.
20
In decimal form, the four bytes are written in the decimal number system, separated by
periods. The IP address is assigned to a host or a network interface. It cannot be used
anywhere else in the world. There are exceptions to this rule, but these are not relevant
in the following passages.
The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses
were strictly categorized in classes. However, this system has proven too inflexible and
was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used.
38.1.2 Netmasks and Routing
Netmasks are used to define the address range of a subnetwork. If two hosts are in the
same subnetwork, they can reach each other directly, if they are not in the same subnetwork, they need the address of a gateway that handles all the traffic between the subnetwork and the rest of the world. To check if two IP addresses are in the same subnet,
simply “AND” both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are differences, the remote IP address,
and thus the remote interface, can only be reached over a gateway.
To understand how the netmask works, look at Example 38.2, “Linking IP Addresses
to the Netmask” (page 552). The netmask consists of 32 bits that identify how much of
an IP address belongs to the network. All those bits that are 1 mark the corresponding
bit in the IP address as belonging to the network. All bits that are 0 mark bits inside
the subnetwork. This means that the more bits are 1, the smaller the subnetwork is.
Because the netmask always consists of several successive 1 bits, it is also possible to
just count the number of bits in the netmask. In Example 38.2, “Linking IP Addresses
to the Netmask” (page 552) the first net with 24 bits could also be written as
192.168.0.0/24.
Basic Networking
551
Example 38.2
Linking IP Addresses to the Netmask
IP address (192.168.0.20): 11000000 10101000 00000000 00010100
Netmask
(255.255.255.0): 11111111 11111111 11111111 00000000
--------------------------------------------------------------Result of the link:
11000000 10101000 00000000 00000000
In the decimal system:
192.
168.
0.
0
IP address (213.95.15.200): 11010101 10111111 00001111 11001000
Netmask
(255.255.255.0): 11111111 11111111 11111111 00000000
--------------------------------------------------------------Result of the link:
11010101 10111111 00001111 00000000
In the decimal system:
213.
95.
15.
0
To give another example: all machines connected with the same ethernet cable are
usually located in the same subnetwork and are directly accessible. Even when the
subnet is physically divided by switches or bridges, these hosts can still be reached directly.
IP addresses outside the local subnet can only be reached if a gateway is configured
for the target network. In the most common case, there is only one gateway that handles
all traffic that is external. However, it is also possible to configure several gateways
for different subnets.
If a gateway has been configured, all external IP packets are sent to the appropriate
gateway. This gateway then attempts to forward the packets in the same manner—from
host to host—until it reaches the destination host or the packet's TTL (time to live) expires.
Table 38.2
552
Specific Addresses
Address Type
Description
Base Network Address
This is the netmask AND any address in the network, as shown
in Example 38.2, “Linking IP Addresses to the Netmask”
(page 552) under Result. This address cannot be assigned to
any hosts.
Broadcast Address
This basically says, “Access all hosts in this subnetwork.” To
generate this, the netmask is inverted in binary form and linked
to the base network address with a logical OR. The above example therefore results in 192.168.0.255. This address cannot
be assigned to any hosts.
Address Type
Description
Local Host
The address 127.0.0.1 is assigned to the “loopback device”
on each host. A connection can be set up to your own machine
with this address.
Because IP addresses must be unique all over the world, you cannot just select random
addresses. There are three address domains to use if you want to set up a private IPbased network. These cannot get any connection from the rest of the Internet, because
they cannot be transmitted over the Internet. These address domains are specified in
RFC 1597 and listed in Table 38.3, “Private IP Address Domains” (page 553).
Table 38.3
Private IP Address Domains
Network/Netmask
Domain
10.0.0.0/255.0.0.0
10.x.x.x
172.16.0.0/255.240.0.0
172.16.x.x – 172.31.x.x
192.168.0.0/255.255.0.0
192.168.x.x
38.2
IPv6—The Next Generation
Internet
Due to the emergence of the WWW (World Wide Web), the Internet has experienced
explosive growth with an increasing number of computers communicating via TCP/IP
in the past fifteen years. Since Tim Berners-Lee at CERN (http://public.web
.cern.ch) invented the WWW in 1990, the number of Internet hosts has grown from
a few thousand to about a hundred million.
As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses
are lost—they cannot be used due to the way in which networks are organized. The
number of addresses available in your subnet is two to the power of the number of bits,
minus two. A subnetwork has, for example, 2, 6, or 14 addresses available. To connect
128 hosts to the Internet, for example, you need a subnetwork with 256 IP addresses,
Basic Networking
553
from which only 254 are usable, because two IP addresses are needed for the structure
of the subnetwork itself: the broadcast and the base network address.
Under the current IPv4 protocol, DHCP or NAT (network address translation) are the
typical mechanisms used to circumvent the potential address shortage. Combined with
the convention to keep private and public address spaces separate, these methods can
certainly mitigate the shortage. The problem with them lies in their configuration, which
is a chore to set up and a burden to maintain. To set up a host in an IPv4 network, you
need a number of address items, such as the host's own IP address, the subnetmask, the
gateway address, and maybe a name server address. All these items need to be known
and cannot be derived from somewhere else.
With IPv6, both the address shortage and the complicated configuration should be a
thing of the past. The following sections tell more about the improvements and benefits
brought by IPv6 and about the transition from the old protocol to the new one.
38.2.1 Advantages
The most important and most visible improvement brought by the new protocol is the
enormous expansion of the available address space. An IPv6 address is made up of 128
bit values instead of the traditional 32 bits. This provides for as many as several
quadrillion IP addresses.
However, IPv6 addresses are not only different from their predecessors with regard to
their length. They also have a different internal structure that may contain more specific
information about the systems and the networks to which they belong. More details
about this are found in Section 38.2.2, “Address Types and Structure” (page 555).
The following is a list of some other advantages of the new protocol:
Autoconfiguration
IPv6 makes the network “plug and play” capable, which means that a newly set up
system integrates into the (local) network without any manual configuration. The
new host uses its automatic configuration mechanism to derive its own address from
the information made available by the neighboring routers, relying on a protocol
called the neighbor discovery (ND) protocol. This method does not require any intervention on the administrator's part and there is no need to maintain a central
server for address allocation—an additional advantage over IPv4, where automatic
address allocation requires a DHCP server.
554
Mobility
IPv6 makes it possible to assign several addresses to one network interface at the
same time. This allows users to access several networks easily, something that could
be compared with the international roaming services offered by mobile phone
companies: when you take your mobile phone abroad, the phone automatically logs
in to a foreign service as soon as it enters the corresponding area, so you can be
reached under the same number everywhere and are able to place an outgoing call
just like in your home area.
Secure Communication
With IPv4, network security is an add-on function. IPv6 includes IPSec as one of
its core features, allowing systems to communicate over a secure tunnel to avoid
eavesdropping by outsiders on the Internet.
Backward Compatibility
Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6
at one time. Therefore, it is crucial that both protocols are able to coexist not only
on the Internet, but also on one system. This is ensured by compatible addresses
(IPv4 addresses can easily be translated into IPv6 addresses) and through the use
of a number of tunnels. See Section 38.2.3, “Coexistence of IPv4 and IPv6”
(page 560). Also, systems can rely on a dual stack IP technique to support both
protocols at the same time, meaning that they have two network stacks that are
completely separate, such that there is no interference between the two protocol
versions.
Custom Tailored Services through Multicasting
With IPv4, some services, such as SMB, need to broadcast their packets to all hosts
in the local network. IPv6 allows a much more fine-grained approach by enabling
servers to address hosts through multicasting—by addressing a number of hosts as
parts of a group (which is different from addressing all hosts through broadcasting
or each host individually through unicasting). Which hosts are addressed as a group
may depend on the concrete application. There are some predefined groups to address
all name servers (the all name servers multicast group), for example, or all routers
(the all routers multicast group).
38.2.2 Address Types and Structure
As mentioned, the current IP protocol is lacking in two important aspects: there is an
increasing shortage of IP addresses and configuring the network and maintaining the
Basic Networking
555
routing tables is becoming a more complex and burdensome task. IPv6 solves the first
problem by expanding the address space to 128 bits. The second one is countered by
introducing a hierarchical address structure, combined with sophisticated techniques
to allocate network addresses, as well as multihoming (the ability to assign several addresses to one device, giving access to several networks).
When dealing with IPv6, it is useful to know about three different types of addresses:
Unicast
Addresses of this type are associated with exactly one network interface. Packets
with such an address are delivered to only one destination. Accordingly, unicast
addresses are used to transfer packets to individual hosts on the local network or
the Internet.
Multicast
Addresses of this type relate to a group of network interfaces. Packets with such an
address are delivered to all destinations that belong to the group. Multicast addresses
are mainly used by certain network services to communicate with certain groups of
hosts in a well-directed manner.
Anycast
Addresses of this type are related to a group of interfaces. Packets with such an address are delivered to the member of the group that is closest to the sender, according
to the principles of the underlying routing protocol. Anycast addresses are used to
make it easier for hosts to find out about servers offering certain services in the
given network area. All servers of the same type have the same anycast address.
Whenever a host requests a service, it receives a reply from the server with the
closest location, as determined by the routing protocol. If this server should fail for
some reason, the protocol automatically selects the second closest server, then the
third one, and so forth.
An IPv6 address is made up of eight four-digit fields, each representing 16 bits, written
in hexadecimal notation. They are also separated by colons (:). Any leading zero bytes
within a given field may be dropped, but zeros within the field or at its end may not.
Another convention is that more than four consecutive zero bytes may be collapsed
into a double colon. However, only one such :: is allowed per address. This kind of
shorthand notation is shown in Example 38.3, “Sample IPv6 Address” (page 557), where
all three lines represent the same address.
556
Example 38.3
Sample IPv6 Address
fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4
fe80 :
0 :
0 :
0 :
0 : 10 : 1000 : 1a4
fe80 :
: 10 : 1000 : 1a4
Each part of an IPv6 address has a defined function. The first bytes form the prefix and
specify the type of address. The center part is the network portion of the address, but
it may be unused. The end of the address forms the host part. With IPv6, the netmask
is defined by indicating the length of the prefix after a slash at the end of the address.
An address, as shown in Example 38.4, “IPv6 Address Specifying the Prefix Length”
(page 557), contains the information that the first 64 bits form the network part of the
address and the last 64 form its host part. In other words, the 64 means that the netmask
is filled with 64 1-bit values from the left. Just like with IPv4, the IP address is combined
with AND with the values from the netmask to determine whether the host is located
in the same subnetwork or in another one.
Example 38.4
IPv6 Address Specifying the Prefix Length
fe80::10:1000:1a4/64
IPv6 knows about several predefined types of prefixes. Some of these are shown in
Table 38.4, “Various IPv6 Prefixes” (page 557).
Table 38.4
Various IPv6 Prefixes
Prefix (hex)
Definition
00
IPv4 addresses and IPv4 over IPv6 compatibility addresses. These
are used to maintain compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into IPv4 packets.
Several special addresses, such as the one for the loopback device,
have this prefix as well.
2 or 3 as the first
digit
Aggregatable global unicast addresses. As is the case with IPv4,
an interface can be assigned to form part of a certain subnetwork.
Currently, there are the following address spaces: 2001::/16
(production quality address space) and 2002::/16 (6to4 address
space).
Basic Networking
557
Prefix (hex)
Definition
fe80::/10
Link-local addresses. Addresses with this prefix should not be
routed and should therefore only be reachable from within the
same subnetwork.
fec0::/10
Site-local addresses. These may be routed, but only within the
network of the organization to which they belong. In effect, they
are the IPv6 equivalent of the current private network address
space, such as 10.x.x.x.
ff
These are multicast addresses.
A unicast address consists of three basic components:
Public Topology
The first part (which also contains one of the prefixes mentioned above) is used to
route packets through the public Internet. It includes information about the company
or institution that provides the Internet access.
Site Topology
The second part contains routing information about the subnetwork to which to deliver the packet.
Interface ID
The third part identifies the interface to which to deliver the packet. This also allows
for the MAC to form part of the address. Given that the MAC is a globally unique,
fixed identifier coded into the device by the hardware maker, the configuration
procedure is substantially simplified. In fact, the first 64 address bits are consolidated
to form the EUI-64 token, with the last 48 bits taken from the MAC, and the remaining 24 bits containing special information about the token type. This also makes
it possible to assign an EUI-64 token to interfaces that do not have a MAC, such
as those based on PPP or ISDN.
On top of this basic structure, IPv6 distinguishes between five different types of unicast
addresses:
:: (unspecified)
This address is used by the host as its source address when the interface is initialized
for the first time—when the address cannot yet be determined by other means.
558
::1 (loopback)
The address of the loopback device.
IPv4 Compatible Addresses
The IPv6 address is formed by the IPv4 address and a prefix consisting of 96 zero
bits. This type of compatibility address is used for tunneling (see Section 38.2.3,
“Coexistence of IPv4 and IPv6” (page 560)) to allow IPv4 and IPv6 hosts to communicate with others operating in a pure IPv4 environment.
IPv4 Addresses Mapped to IPv6
This type of address specifies a pure IPv4 address in IPv6 notation.
Local Addresses
There are two address types for local use:
link-local
This type of address can only be used in the local subnetwork. Packets with a
source or target address of this type should not be routed to the Internet or other
subnetworks. These addresses contain a special prefix (fe80::/10) and the
interface ID of the network card, with the middle part consisting of zero bytes.
Addresses of this type are used during automatic configuration to communicate
with other hosts belonging to the same subnetwork.
site-local
Packets with this type of address may be routed to other subnetworks, but not
to the wider Internet—they must remain inside the organization's own network.
Such addresses are used for intranets and are an equivalent of the private address
space defined by IPv4. They contain a special prefix (fec0::/10), the interface
ID, and a 16 bit field specifying the subnetwork ID. Again, the rest is filled with
zero bytes.
As a completely new feature introduced with IPv6, each network interface normally
gets several IP addresses, with the advantage that several networks can be accessed
through the same interface. One of these networks can be configured completely automatically using the MAC and a known prefix with the result that all hosts on the local
network can be reached as soon as IPv6 is enabled (using the link-local address). With
the MAC forming part of it, any IP address used in the world is unique. The only variable
parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating.
Basic Networking
559
For a host to go back and forth between different networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identifier of the home network to which it normally belongs (and the corresponding prefix).
The home address is a static address and, as such, it does not normally change. Still,
all packets destined to the mobile host can be delivered to it, regardless of whether it
operates in the home network or somewhere outside. This is made possible by the
completely new features introduced with IPv6, such as stateless autoconfiguration and
neighbor discovery. In addition to its home address, a mobile host gets one or more
additional addresses that belong to the foreign networks where it is roaming. These are
called care-of addresses. The home network has a facility that forwards any packets
destined to the host when it is roaming outside. In an IPv6 environment, this task is
performed by the home agent, which takes all packets destined to the home address and
relays them through a tunnel. On the other hand, those packets destined to the care-of
address are directly transferred to the mobile host without any special detours.
38.2.3 Coexistence of IPv4 and IPv6
The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual
process. Both protocols will coexist for some time to come. The coexistence on one
system is guaranteed where there is a dual stack implementation of both protocols. That
still leaves the question of how an IPv6 enabled host should communicate with an IPv4
host and how IPv6 packets should be transported by the current networks, which are
predominantly IPv4 based. The best solutions offer tunneling and compatibility addresses
(see Section 38.2.2, “Address Types and Structure” (page 555)).
IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them
across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel.
To achieve this, packets must include the IPv6 destination address (or the corresponding
prefix) as well as the IPv4 address of the remote host at the receiving end of the tunnel.
A basic tunnel can be configured manually according to an agreement between the
hosts' administrators. This is also called static tunneling.
However, the configuration and maintenance of static tunnels is often too labor-intensive
to use them for daily communication needs. Therefore, IPv6 provides for three different
methods of dynamic tunneling:
560
6over4
IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4
network capable of multicasting. IPv6 is tricked into seeing the whole network
(Internet) as a huge local area network (LAN). This makes it possible to determine
the receiving end of the IPv4 tunnel automatically. However, this method does not
scale very well and is also hampered by the fact that IP multicasting is far from
widespread on the Internet. Therefore, it only provides a solution for smaller corporate or institutional networks where multicasting can be enabled. The specifications
for this method are laid down in RFC 2529.
6to4
With this method, IPv4 addresses are automatically generated from IPv6 addresses,
enabling isolated IPv6 hosts to communicate over an IPv4 network. However, a
number of problems have been reported regarding the communication between those
isolated IPv6 hosts and the Internet. The method is described in RFC 3056.
IPv6 Tunnel Broker
This method relies on special servers that provide dedicated tunnels for IPv6 hosts.
It is described in RFC 3053.
IMPORTANT: The 6bone Initiative
In the heart of the “old-time” Internet, there is already a globally distributed
network of IPv6 subnets that are connected through tunnels. This is the 6bone
network (http://www.6bone.net), an IPv6 test environment that may be
used by programmers and Internet providers who want to develop and offer
IPv6-based services to gain the experience necessary to implement the new
protocol. More information can be found on the project's Internet site.
38.2.4 Configuring IPv6
To configure IPv6, you do not normally need to make any changes on the individual
workstations. However, IPv6 support must be loaded. To do this, enter modprobe ipv6
as root.
Because of the autoconfiguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on
a workstation. The network routers can be queried by the workstation, using the router
advertisement protocol, for what prefix and gateways should be implemented. The
Basic Networking
561
radvd program can be used to set up an IPv6 router. This program informs the workstations which prefix to use for the IPv6 addresses and which routers. Alternatively, use
zebra for automatic configuration of both addresses and routing.
Consult the ifup(8) man page to get information about how to set up various types of
tunnels using the /etc/sysconfig/network files.
38.2.5 For More Information
The above overview does not cover the topic of IPv6 comprehensively. For a more indepth look at the new protocol, refer to the following online documentation and books:
http://www.ngnet.it/e/cosa-ipv6.php
An article series providing a well-written introduction to the basics of IPv6. A good
primer on the topic.
http://www.bieringer.de/linux/IPv6/
Here, find the Linux IPv6-HOWTO and many links related to the topic.
http://www.6bone.net/
Visit this site if you want to join a tunneled IPv6 network.
http://www.ipv6.org/
The starting point for everything about IPv6.
RFC 2640
The fundamental RFC about IPv6.
IPv6 Essentials
A book describing all the important aspects of the topic is IPv6 Essentials by Silvia
Hagen (ISBN 0-596-00125-8).
38.3
Name Resolution
DNS assists in assigning an IP address to one or more names and assigning a name to
an IP address. In Linux, this conversion is usually carried out by a special type of software known as bind. The machine that takes care of this conversion is called a name
server. The names make up a hierarchical system in which each name component is
562
separated by dots. The name hierarchy is, however, independent of the IP address hierarchy described above.
Consider a complete name, such as earth.example.com, written in the format
hostname.domain. A full name, referred to as a fully qualified domain name
(FQDN), consists of a hostname and a domain name (example.com). The latter also
includes the top level domain or TLD (com).
TLD assignment has become quite confusing for historical reasons. Traditionally, threeletter domain names are used in the USA. In the rest of the world, the two-letter ISO
national codes are the standard. In addition to that, longer TLDs were introduced in
2000 that represent certain spheres of activity (for example, .info, .name, .museum).
In the early days of the Internet (before 1990), the file /etc/hosts was used to store
the names of all the machines represented over the Internet. This quickly proved to be
impractical in the face of the rapidly growing number of computers connected to the
Internet. For this reason, a decentralized database was developed to store the hostnames
in a widely distributed manner. This database, similar to the name server, does not have
the data pertaining to all hosts in the Internet readily available, but can dispatch requests
to other name servers.
The top of the hierarchy is occupied by root name servers. These root name servers
manage the top level domains and are run by the Network Information Center (NIC).
Each root name server knows about the name servers responsible for a given top level
domain. Information about top level domain NICs is available at http://www
.internic.net.
DNS can do more than just resolve hostnames. The name server also knows which host
is receiving e-mails for an entire domain—the mail exchanger (MX).
For your machine to resolve an IP address, it must know about at least one name server
and its IP address. Easily specify such a name server with the help of YaST. If you have
a modem dial-up connection, you may not need to configure a name server manually
at all. The dial-up protocol provides the name server address as the connection is made.
The configuration of name server access with SUSE Linux is described in Chapter 40,
The Domain Name System (page 593).
The protocol whois is closely related to DNS. With this program, quickly find out
who is responsible for any given domain.
Basic Networking
563
38.4
Configuring a Network
Connection with YaST
There are many supported networking types on Linux. Most of them use different device
names and the configuration files are spread over several locations in the file system.
For a detailed overview of the aspects of manual network configuration, see Section 38.5,
“Configuring a Network Connection Manually” (page 574).
During installation, YaST can be used to configure automatically all interfaces that
have been detected. Additional hardware can be configured any time after installation
in the installed system. The following sections describe the network configuration for
all types of network connections supported by SUSE Linux.
38.4.1 Configuring the Network Card with
YaST
After starting the module, YaST displays a general network configuration dialog. The
upper part shows a list with all the network cards yet to be configured. Any card properly detected is listed with its name. Devices that could not be detected may be configured using Add as described in Section “Manual Configuration of an Undetected Network
Card” (page 564). Configure a new network card or change an existing configuration.
Manual Configuration of an Undetected Network
Card
Configuring a network card that was not detected includes the following items:
Network Configuration
Set the device type of the interface from the available options and the configuration
name. Information about the naming conventions for configuration names is available
in the getcfg(8) man page.
Kernel Module
Hardware Configuration Name specifies the name of the /etc/sysconfig/
hardware/hwcfg-* file containing the hardware settings of your network card.
This contains the name of the suitable kernel module as well as the needed options
564
to initialize the hardware. Usually, YaST proposes useful names for PCMCIA and
USB hardware. For other hardware, hwcfg-static-0 usually only makes sense
if the card is configured with the configuration name 0.
If the network card is a PCMCIA or USB device, activate the respective check
boxes and exit this dialog with Next. Otherwise, select your network card model
from Select from List. YaST then automatically selects the suitable kernel module
for the card. Exit this dialog with Next.
Figure 38.3
Configuration of the Network Card
Setting the Network Address
Set the device type of the interface and the configuration name. Select the device type
from those provided. Specify a configuration name according to your needs. Usually,
the default settings are useful and can be accepted. Information about the naming conventions for configuration names is available in the getcfg(8) man page .
If you selected Wireless as the device type of the interface, configure the operating
mode, the network name (ESSID), and the encryption in the next dialog, Wireless
Network Card Configuration. Click OK to complete the configuration of your card. A
detailed description of the configuration of WLAN cards is provided in Section 22.1.3,
Basic Networking
565
“Configuration with YaST” (page 288). For all other interface types, proceed with the
network address setup:
Automatic Address Setup (via DHCP)
If your network includes a DHCP server, you can rely on it to set up your network
address automatically. The option should also be used if you are using a DSL line
but with no static IP assigned by the ISP. If you decide to use DHCP, configure the
details after selecting DHCP Client Options. Specify whether the DHCP server
should always honor broadcast requests and any identifier to use. By default, DHCP
servers use the card's hardware address to identify an interface. If you have a virtual
host setup where different hosts communicate through the same interface, an identifier is necessary to distinguish them.
Static Address Setup
If you have a static address, enable that option. Then enter the address and subnet
mask for your network. The preset subnet mask should match the requirements of
a typical home network.
Leave this dialog by selecting Next or proceed to configure the hostname, name server,
and routing details (see the sections on DNS Server (↑Start-Up) and Routing (↑StartUp)).
Advanced enables you to specify more complex settings. Under Detailed Settings, use
User Controlled to delegate the control over the network card from the administrator
(root) to the normal user. For mobile operation, this allows the user to adapt changing
network connections in a more flexible way, because he can control the activation or
deactivation of the interface. The MTU (maximum transmission unit) and the type of
Device Activation can also be set in this dialog.
38.4.2 Modem
In the YaST Control Center, access the modem configuration under Network Devices.
If your modem was not automatically detected, open the dialog for manual configuration.
In the dialog that opens, enter the interface to which the modem is connected under
Modem.
566
Figure 38.4
Modem Configuration
If you are behind a private branch exchange (PBX), you may need to enter a dial prefix.
This is often a zero. Consult the instructions that came with the PBX to find out. Also
select whether to use tone or pulse dialing, whether the speaker should be on, and
whether the modem should wait until it detects a dial tone. The last option should not
be enabled if the modem is connected to an exchange.
Under Details, set the baud rate and the modem initialization strings. Only change these
settings if your modem was not autodetected or if it requires special settings for data
transmission to work. This is mainly the case with ISDN terminal adapters. Leave this
dialog by clicking OK. To delegate control over the modem to the normal user without
root permissions, activate User Controlled. In this way, a user without administrator
permissions can activate or deactivate an interface. Under Dial Prefix Regular Expression, specify a regular expression. The Dial Prefix in KInternet, which can be modified
by the normal user, must match this regular expression. If this field is left empty, the
user cannot set a different Dial Prefix without administrator permissions.
In the next dialog, select the ISP (Internet service provider). To choose from a predefined
list of ISPs operating in your country, select Country. Alternatively, click New to open
a dialog in which to provide the data for your ISP. This includes a name for the dial-up
connection and ISP as well as the login and password provided by your ISP. Enable
Always Ask for Password to be prompted for the password each time you connect.
Basic Networking
567
In the last dialog, specify additional connection options:
Dial on Demand
If you enable dial on demand, set at least one name server.
Modify DNS when Connected
This option is enabled by default, with the effect that the name server address is
updated each time you connect to the Internet.
Automatically Retrieve DNS
If the provider does not transmit its domain name server after connecting, disable
this option and enter the DNS data manually.
Stupid Mode
This option is enabled by default. With it, input prompts sent by the ISP's server
are ignored to prevent them from interfering with the connection process.
External Firewall Interface and Restart Firewall
Selecting these options enables the SUSEfirewall2, which protects you from outside
attacks for the duration of your Internet connection.
Idle Time-Out (seconds)
With this option, specify a period of network inactivity after which the modem
disconnects automatically.
IP Details
This opens the address configuration dialog. If your ISP does not assign a dynamic
IP address to your host, disable Dynamic IP Address then enter your host's local IP
address and the remote IP address. Ask your ISP for this information. Leave Default
Route enabled and close the dialog by selecting OK.
Selecting Next returns to the original dialog, which displays a summary of the modem
configuration. Close this dialog with Finish.
38.4.3 ISDN
Use this module to configure one or several ISDN cards for your system. If YaST did
not detect your ISDN card, manually select it. Multiple interfaces are possible, but
several ISPs can be configured for one interface. In the subsequent dialogs, set the ISDN
options necessary for the proper functioning of the card.
568
Figure 38.5
ISDN Configuration
In the next dialog, shown in Figure 38.5, “ISDN Configuration” (page 569), select the
protocol to use. The default is Euro-ISDN (EDSS1), but for older or larger exchanges,
select 1TR6. If you are in the US, select NI1. Select your country in the relevant field.
The corresponding country code then appears in the field next to it. Finally, provide
your Area Code and the Dial Prefix if necessary.
Start Mode defines how the ISDN interface should be started: At Boot Time causes the
ISDN driver to be initialized each time the system boots. Manually requires you to load
the ISDN driver as root with the command rcisdn start. On Hotplug, used for
PCMCIA or USB devices, loads the driver after the device is plugged in. When finished
with these settings, select OK.
In the next dialog, specify the interface type for your ISDN card and add ISPs to an
existing interface. Interfaces may be either the SyncPPP or the RawIP type, but most
ISPs operate in the SyncPPP mode, which is described below.
Basic Networking
569
Figure 38.6
ISDN Interface Configuration
The number to enter for My Phone Number depends on your particular setup:
ISDN Card Directly Connected to Phone Outlet
A standard ISDN line provides three phone numbers (called multiple subscriber
numbers, or MSNs). If the subscriber asked for more, there may be up to 10. One
of these MSNs must be entered here, but without your area code. If you enter the
wrong number, your phone operator automatically falls back to the first MSN assigned to your ISDN line.
ISDN Card Connected to a Private Branch Exchange
Again, the configuration may vary depending on the equipment installed:
1.
Smaller private branch exchanges (PBX) built for home purposes mostly use
the Euro-ISDN (EDSS1) protocol for internal calls. These exchanges have an
internal S0 bus and use internal numbers for the equipment connected to them.
Use one of the internal numbers as your MSN. You should be able to use at
least one of the exchange's MSNs that have been enabled for direct outward
dialing. If this does not work, try a single zero. For further information, consult
the documentation that came with your phone exchange.
570
2.
Larger phone exchanges designed for businesses normally use the 1TR6 protocol for internal calls. Their MSN is called EAZ and usually corresponds to
the direct-dial number. For the configuration under Linux, it should be sufficient
to enter the last digit of the EAZ. As a last resort, try each of the digits from 1
to 9.
For the connection to be terminated just before the next charge unit is due, enable
ChargeHUP. However, remember that may not work with every ISP. You can also
enable channel bundling (multilink PPP) by selecting the corresponding option. Finally,
you can enable SuSEfirewall2 for your link by selecting External Firewall Interface
and Restart Firewall. To enable the normal user without administrator permissions to
activate or deactivate the interface, select the User Controlled.
Details opens a dialog in which to implement more complex connection schemes, which
are not relevant for normal home users. Leave the Details dialog by selecting OK.
In the next dialog, make IP address settings. If you have not been given a static IP by
your provider, select Dynamic IP Address. Otherwise, use the fields provided to enter
your host's local IP address and the remote IP address according to the specifications
of your ISP. If the interface should be the default route to the Internet, select Default
Route. Each host can only have one interface configured as the default route. Leave
this dialog by selecting Next.
The following dialog allows you to set your country and select an ISP. The ISPs included
in the list are call-by-call providers only. If your ISP is not in the list, select New. This
opens the Provider Parameters dialog in which to enter all the details for your ISP.
When entering the phone number, do not include any blanks or commas among the
digits. Finally, enter your login and the password as provided by the ISP. When finished,
select Next.
To use Dial on Demand on a stand-alone workstation, also specify the name server
(DNS server). Most ISPs support dynamic DNS, which means the IP address of a name
server is sent by the ISP each time you connect. For a single workstation, however, you
still need to provide a placeholder address like 192.168.22.99. If your ISP does
not support dynamic DNS, specify the name server IP addresses of the ISP. If desired,
specify a time-out for the connection—the period of network inactivity (in seconds)
after which the connection should be automatically terminated. Confirm your settings
with Next. YaST displays a summary of the configured interfaces. To make all these
settings active, select Finish.
Basic Networking
571
38.4.4 Cable Modem
In some countries, such as Austria and the US, it is quite common to access the Internet
through the TV cable network. The TV cable subscriber usually gets a modem that is
connected to the TV cable outlet on one side and to a computer network card on the
other (using a 10Base-TG twisted pair cable). The cable modem then provides a dedicated Internet connection with a fixed IP address.
Depending on the instructions provided by your ISP, when configuring the network
card either select Automatic Address Setup (via DHCP) or Static Address Setup. Most
providers today use DHCP. A static IP address often comes as part of a special business
account.
38.4.5 DSL
To configure your DSL device, select the DSL module from the YaST Network Devices
section. This YaST module consists of several dialogs in which to set the parameters
of DSL links based on one of the following protocols:
• PPP over Ethernet (PPPoE)
• PPP over ATM (PPPoATM)
• CAPI for ADSL (Fritz Cards)
• Point-to-Point Tunneling Protocol (PPTP)—Austria
The configuration of a DSL connection based on PPPoE or PPTP requires that the
corresponding network card has already been set up in the correct way. If you have not
done so yet, first configure the card by selecting Configure Network Cards (see Section 38.4.1, “Configuring the Network Card with YaST” (page 564)). In the case of a
DSL link, addresses may be assigned automatically but not via DHCP, which is why
you should not enable the option Automatic address setup (via DHCP). Instead, enter
a static dummy address for the interface, such as 192.168.22.1. In Subnet Mask,
enter 255.255.255.0. If you are configuring a stand-alone workstation, leave Default
Gateway empty.
572
TIP
Values in IP Address and Subnet Mask are only placeholders. They are only
needed to initialize the network card and do not represent the DSL link as such.
Figure 38.7
DSL Configuration
To begin the DSL configuration (see Figure 38.7, “DSL Configuration” (page 573)),
first select the PPP mode and the ethernet card to which the DSL modem is connected
(in most cases, this is eth0). Then use Device Activation to specify whether the DSL
link should be established during the boot process. Click User Controlled to authorize
the normal user without root permissions to activate or deactivate the interface with
KInternet. The dialog also lets you select your country and choose from a number of
ISPs operating in it. The details of any subsequent dialogs of the DSL configuration
depend on the options set so far, which is why they are only briefly mentioned in the
following paragraphs. For details on the available options, read the detailed help
available from the dialogs.
To use Dial on Demand on a stand-alone workstation, also specify the name server
(DNS server). Most ISPs support dynamic DNS—the IP address of a name server is
sent by the ISP each time you connect. For a single workstation, however, provide a
placeholder address like 192.168.22.99. If your ISP does not support dynamic
DNS, enter the name server IP address provided by your ISP.
Basic Networking
573
Idle Time-Out (seconds) defines a period of network inactivity after which to terminate
the connection automatically. A reasonable time-out value is between 60 and 300 seconds. If Dial on Demand is disabled, it may be useful to set the time-out to zero to
prevent automatic hang-up.
The configuration of T-DSL is very similar to the DSL setup. Just select T-Online as
your provider and YaST opens the T-DSL configuration dialog. In this dialog, provide
some additional information required for T-DSL—the line ID, the T-Online number,
the user code, and your password. All of these should be included in the information
you received after subscribing to T-DSL.
38.5
Configuring a Network
Connection Manually
Manual configuration of the network software should always be the last alternative.
Using YaST is recommended. However, this background information about the network
configuration can also assist your work with YaST.
All built-in network cards and hotplug network cards (PCMCIA, USB, some PCI cards)
are detected and configured via hotplug. The system sees a network card in two different
ways: first as a physical device and second as an interface. The insertion or detection
of a device triggers a hotplug event. This hotplug event triggers the initialization of the
device with the script hwup. When the network card is initialized as a new network
interface, the kernel generates another hotplug event that triggers the setup of the interface with ifup.
The kernel numbers interface names according to the temporal order of their registration.
The initialization sequence is decisive for the assignment of names. If one of several
network card fails, the numbering of all subsequently initialized cards is shifted. For
real hotpluggable cards, the order in which the devices are connected is what matters.
To achieve a flexible configuration, the configuration of the device (hardware) and the
interface has been separated and the mapping of configurations to devices and interfaces
is no longer managed on the basis of the interface names. The device configurations
are located in /etc/sysconfig/hardware/hwcfg-*. The interface configurations are located in /etc/sysconfig/network/ifcfg-*. The names of the
configurations are assigned in such a way that they describe the devices and interfaces
with which they are associated. Because the former mapping of drivers to interface
574
name required static interface names, this mapping can no longer take place in /etc/
modprobe.conf. In the new concept, alias entries in this file would cause undesirable
side effects.
The configuration names—everything after hwcfg- or ifcfg-—can describe the
devices by means of the slot, a device-specific ID, or the interface name. For example,
the configuration name for a PCI card could be bus-pci-0000:02:01.0 (PCI
slot) or vpid-0x8086-0x1014-0x0549 (vendor and product ID). The name of
the associated interface could be bus-pci-0000:02:01.0 or
wlan-id-00:05:4e:42:31:7a (MAC address).
To assign a certain network configuration to any card of a certain type (of which only
one is inserted at a time) instead of a certain card, select less specific configuration
names. For example, bus-pcmcia would be used for all PCMCIA cards. On the
other hand, the names can be limited by a preceding interface type. For example,
wlan-bus-usb would be assigned to WLAN cards connected to a USB port.
The system always uses the configuration that best describes an interface or the device
providing the interface. The search for the most suitable configuration is handled by
getcfg. The output of getcfg delivers all information that can be used for describing
a device. Details regarding the specification of configuration names are available in the
manual page of getcfg.
With the described method, a network interface is configured with the correct configuration even if the network devices are not always initialized in the same order. However,
the name of the interface still depends on the initialization sequence. There are two
ways to ensure reliable access to the interface of a certain network card:
• getcfg-interface configuration name returns the name of the associated network interface. Therefore, the configuration name, such as firewall, dhcpd,
routing, or various virtual network interfaces (tunnels), can be entered in some
configuration files instead of the interface name, which is not persistent.
• Persistent interface names are assigned to each interface automatically. You may
adjust them to suit your needs. When creating interface names, proceed as outlined
in /etc/udev/rules.d/30-net_persistent_names.rules. However,
the persistent name pname should not be the same as the name that would automatically be assigned by the kernel. Therefore, eth*, tr*, wlan*, and so on are not
permitted. Instead, use net* or descriptive names like external, internal,
or dmz. Make sure that the same interface name is not used twice. Allowed charac-
Basic Networking
575
ters in interface names are restricted to [a-zA-Z0-9]. A persistent name can
only be assigned to an interface immediately after its registration, which means
that the driver of the network card must be reloaded or hwup device
description must be executed. The command rcnetwork restart is not
sufficient for this purpose.
IMPORTANT: Using Persistent Interface Names
The use of persistent interface names has not been tested in all areas.
Therefore, some applications may not be able to handle freely selected
interface names.
ifup requires an existing interface, because it does not initialize the hardware. The
initialization of the hardware is handled by the command hwup (executed by hotplug
or coldplug). When a device is initialized, ifup is automatically executed for the
new interface via hotplug and the interface is set up if the start mode is onboot,
hotplug, or auto and the network service was started. Formerly, the command
ifup interfacename triggered the hardware initialization. Now the procedure has
been reversed. First, a hardware component is initialized then all other actions follow.
In this way, a varying number of devices can always be configured in the best way
possible with an existing set of configurations.
Table 38.5, “Manual Network Configuration Scripts” (page 576) summarizes the most
important scripts involved in the network configuration. Where possible, the scripts are
distinguished by hardware and interface.
Table 38.5
576
Manual Network Configuration Scripts
Configuration Stage
Command
Function
Hardware
hw{up,down,status} The hw* scripts are executed by the hotplug subsystem to initialize a device, undo the initialization, or query the status
of a device. More information is available
in the manual page of hwup.
Interface
getcfg
getcfg can be used to query the interface name associated with a configuration
Configuration Stage
Command
Function
name or a hardware description. More
information is available in the manual
page of getcfg.
Interface
if{up,down,status} The if* scripts start existing network
interfaces or return the status of the
specified interface. More information is
available in the manual page of ifup.
More information about hotplug and persistent device names is available in Chapter 32,
The Hotplug System (page 485) and Chapter 33, Dynamic Device Nodes with udev
(page 491).
38.5.1 Configuration Files
This section provides an overview of the network configuration files and explains their
purpose and the format used.
/etc/syconfig/hardware/hwcfg-*
These files contain the hardware configurations of network cards and other devices.
They contain the needed parameters, such as the kernel module, start mode, and script
associations. Refer to the manual page of hwup for details. Regardless of the existing
hardware, the hwcfg-static-* configurations are applied when coldplug is started.
/etc/sysconfig/network/ifcfg-*
These files contain the configurations for network interface. They include information
such as the start mode and the IP address. Possible parameters are described in the
manual page of ifup. Additionally, all variables from the files dhcp, wireless,
and config can be used in the ifcfg-* files if a general setting should be used for
only one interface.
Basic Networking
577
/etc/sysconfig/network/config, dhcp,
wireless
The file config contains general settings for the behavior of ifup, ifdown, and
ifstatus. dhcp contains settings for DHCP and wireless for wireless LAN
cards. The variables in all three configuration files are commented and can also be used
in ifcfg-* files, where they are treated with higher priority.
/etc/sysconfig/network/routes,ifroute-*
The static routing of TCP/IP packets is determined here. All the static routes required
by the various system tasks can be entered in the /etc/sysconfig/network/
routes file: routes to a host, routes to a host via a gateway, and routes to a network.
For each interface that needs individual routing, define an additional configuration file:
/etc/sysconfig/network/ifroute-*. Replace * with the name of the interface. The entries in the routing configuration files look like this:
# Destination
#
127.0.0.0
204.127.235.0
default
207.68.156.51
192.168.0.0
Dummy/Gateway
Netmask
Device
0.0.0.0
0.0.0.0
204.127.235.41
207.68.145.45
207.68.156.51
255.255.255.0
255.255.255.0
0.0.0.0
255.255.255.255
255.255.0.0
lo
eth0
eth0
eth1
eth1
The route's destination is in the first column. This column may contain the IP address
of a network or host or, in the case of reachable name servers, the fully qualified network
or hostname.
The second column contains the default gateway or a gateway through which a host or
network can be accessed. The third column contains the netmask for networks or hosts
behind a gateway. For example, the mask is 255.255.255.255 for a host behind a
gateway.
The fourth column is only relevant for networks connected to the local host such as
loopback, Ethernet, ISDN, PPP, and dummy device. The device name must be entered
here.
An (optional) fifth column can be used to specify the type of a route. Columns that are
not needed should contain a minus sign - to ensure that the parser correctly interprets
the command. For details, refer to the routes(5) man page.
578
/etc/resolv.conf
The domain to which the host belongs is specified in this file (keyword search). Also
listed is the status of the name server address to access (keyword nameserver).
Multiple domain names can be specified. When resolving a name that is not fully
qualified, an attempt is made to generate one by attaching the individual search entries.
Use multiple name servers by entering several lines, each beginning with nameserver.
Precede comments with # signs. YaST enters the specified name server in this file.
Example 38.5, “/etc/resolv.conf” (page 579) shows what /etc/resolv.conf
could look like.
Example 38.5
/etc/resolv.conf
# Our domain
search example.com
#
# We use sun (192.168.0.20) as nameserver
nameserver 192.168.0.20
Some services, like pppd (wvdial), ipppd (isdn), dhcp (dhcpcd and
dhclient), pcmcia, and hotplug, modify the file /etc/resolv.conf by
means of the script modify_resolvconf. If the file /etc/resolv.conf has
been temporarily modified by this script, it contains a predefined comment giving information about the service that modified it, the location where the original file has
been backed up, and how to turn off the automatic modification mechanism. If /etc/
resolv.conf is modified several times, the file includes modifications in a nested
form. These can be reverted in a clean way even if this reversal takes place in an order
different from the order in which modifications were introduced. Services that may
need this flexibility include isdn, pcmcia, and hotplug.
If a service was not terminated in a normal, clean way, modify_resolvconf can
be used to restore the original file. Also, on system boot, a check is performed to see
whether there is an uncleaned, modified resolv.conf, for example, after a system
crash, in which case the original (unmodified) resolv.conf is restored.
YaST uses the command modify_resolvconf check to find out whether resolv
.conf has been modified and subsequently warns the user that changes will be lost
after restoring the file. Apart from this, YaST does not rely on modify_resolvconf,
which means that the impact of changing resolv.conf through YaST is the same
as that of any manual change. In both cases, changes have a permanent effect. Modifications requested by the mentioned services are only temporary.
Basic Networking
579
/etc/hosts
In this file, shown in Example 38.6, “/etc/hosts” (page 580), IP addresses are assigned to hostnames. If no name server is implemented, all hosts to which an IP connection will be set up must be listed here. For each host, enter a line consisting of the IP
address, the fully qualified hostname, and the hostname into the file. The IP address
must be at the beginning of the line and the entries separated by blanks and tabs.
Comments are always preceded by the # sign.
Example 38.6
/etc/hosts
127.0.0.1 localhost
192.168.0.20 sun.example.com sun
192.168.0.0 earth.example.com earth
/etc/networks
Here, network names are converted to network addresses. The format is similar to that
of the hosts file, except the network names precede the addresses. See Example 38.7,
“/etc/networks” (page 580).
Example 38.7
loopback
localnet
/etc/networks
127.0.0.0
192.168.0.0
/etc/host.conf
Name resolution—the translation of host and network names via the resolver library—is
controlled by this file. This file is only used for programs linked to libc4 or libc5. For
current glibc programs, refer to the settings in /etc/nsswitch.conf. A parameter
must always stand alone in its own line. Comments are preceded by a # sign. Table 38.6,
“Parameters for /etc/host.conf” (page 580) shows the parameters available. A sample
/etc/host.conf is shown in Example 38.8, “ /etc/host.conf ” (page 581).
Table 38.6
Parameters for /etc/host.conf
order hosts, bind
580
Specifies in which order the services are accessed for the name
resolution. Available arguments are (separated by blank spaces
or commas):
hosts: Searches the /etc/hosts file
bind: Accesses a name server
nis: Uses NIS
multi on/off
Defines if a host entered in /etc/hosts can have multiple
IP addresses.
nospoof on
spoofalert on/off
These parameters influence the name server spoofing, but,
apart from that, do not exert any influence on the network
configuration.
trim domainname
The specified domain name is separated from the hostname
after hostname resolution (as long as the hostname includes
the domain name). This option is useful if only names from
the local domain are in the /etc/hosts file, but should still
be recognized with the attached domain names.
Example 38.8
/etc/host.conf
# We have named running
order hosts bind
# Allow multiple addrs
multi on
/etc/nsswitch.conf
The introduction of the GNU C Library 2.0 was accompanied by the introduction of
the Name Service Switch (NSS). Refer to the nsswitch.conf(5) man page and
The GNU C Library Reference Manual for details.
The order for queries is defined in the file /etc/nsswitch.conf. A sample
nsswitch.conf is shown in Example 38.9, “/etc/nsswitch.conf” (page 582).
Comments are introduced by # signs. In this example, the entry under the hosts
database means that a request is sent to /etc/hosts (files) via DNS (see Chapter 40, The Domain Name System (page 593)).
Basic Networking
581
Example 38.9
/etc/nsswitch.conf
passwd:
group:
compat
compat
hosts:
networks:
files dns
files dns
services:
protocols:
db files
db files
netgroup:
automount:
files
files nis
The “databases” available over NSS are listed in Table 38.7, “Databases Available via
/etc/nsswitch.conf” (page 582). In addition, automount, bootparams, netmasks,
and publickey are expected in the near future. The configuration options for NSS
databases are listed in Table 38.8, “Configuration Options for NSS “Databases””
(page 583).
Table 38.7
582
Databases Available via /etc/nsswitch.conf
aliases
Mail aliases implemented by sendmail; see man 5
aliases.
ethers
Ethernet addresses.
group
For user groups, used by getgrent. See also the man page
for group.
hosts
For hostnames and IP addresses, used by gethostbyname
and similar functions.
netgroup
Valid host and user lists in the network for the purpose of
controlling access permissions; see the netgroup(5) man
page.
networks
Network names and addresses, used by getnetent.
passwd
User passwords, used by getpwent; see the passwd(5)
man page.
protocols
Network protocols, used by getprotoent; see the
protocols(5) man page.
rpc
Remote procedure call names and addresses, used by
getrpcbyname and similar functions.
services
Network services, used by getservent.
shadow
Shadow passwords of users, used by getspnam; see the
shadow(5) man page.
Table 38.8
Configuration Options for NSS “Databases”
files
directly access files, for example, /etc/aliases
db
access via a database
nis, nisplus
NIS, see also Chapter 41, Using NIS (page 615)
dns
can only be used as an extension for hosts and
networks
compat
can only be used as an extension for passwd, shadow,
and group
/etc/nscd.conf
This file is used to configure nscd (name service cache daemon). See the nscd(8)
and nscd.conf(5) man pages. By default, the system entries of passwd and
groups are cached by nscd. This is important for the performance of directory services,
like NIS and LDAP, because otherwise the network connection needs to be used for
every access to names or groups. hosts is not cached by default, because the mechanism in nscd to cache hosts makes the local system unable to trust forward and reverse
lookup checks. Instead of asking nscd to cache names, set up a caching DNS server.
If the caching for passwd is activated, it usually takes about fifteen seconds until a
newly added local user is recognized. Reduce this waiting time by restarting nscd with
the command rcnscd restart.
Basic Networking
583
/etc/HOSTNAME
This contains the hostname without the domain name attached. This file is read by
several scripts while the machine is booting. It may only contain one line in which the
hostname is set.
38.5.2 Start-Up Scripts
Apart from the configuration files described above, there are also various scripts that
load the network programs while the machine is booting. These are started as soon as
the system is switched to one of the multiuser runlevels. Some of these scripts are described in Table 38.9, “Some Start-Up Scripts for Network Programs” (page 584).
Table 38.9
Some Start-Up Scripts for Network Programs
/etc/init.d/network This script handles the configuration of the network
interfaces. The hardware must already have been initialized by /etc/init.d/coldplug (via
hotplug). If the network service was not started,
no network interfaces are implemented when they are
inserted via hotplug.
/etc/init.d/inetd
Starts xinetd. xinetd can be used to make server services available on the system. For example, it can
start vsftpd whenever an FTP connection is initiated.
/etc/init.d/portmap Starts the portmapper needed for the RPC server, such
as an NFS server.
584
/etc/init.d/
nfsserver
Starts the NFS server.
/etc/init.d/
sendmail
Controls the sendmail process.
/etc/init.d/ypserv
Starts the NIS server.
/etc/init.d/ypbind
Starts the NIS client.
38.6
smpppd as Dial-up Assistant
Most home users do not have a dedicated line connecting them to the Internet. Instead,
they use dial-up connections. Depending on the dial-up method (ISDN or DSL), the
connection is controlled by ipppd or pppd. Basically, all that needs to be done to go
online is to start these programs correctly.
If you have a flat-rate connection that does not generate any additional costs for the
dial-up connection, simply start the respective daemon. Control the dial-up connection
with a KDE applet or a command-line interface. If the Internet gateway is not the host
you are using, you might want to control the dial-up connection by way of a network
host.
This is where smpppd is involved. It provides a uniform interface for auxiliary programs
and acts in two directions. First, it programs the required pppd or ipppd and controls
its dial-up properties. Second, it makes various providers available to the user programs
and transmits information about the current status of the connection. As smpppd can
also be controlled by way of the network, it is suitable for controlling dial-up connections
to the Internet from a workstation in a private subnetwork.
38.6.1 Configuring smpppd
The connections provided by smpppd are automatically configured by YaST. The actual
dial-up programs KInternet and cinternet are also preconfigured. Manual settings are
only required to configure additional features of smpppd, such as remote control.
The configuration file of smpppd is /etc/smpppd.conf. By default, it does not
enable remote control. The most important options of this configuration file are:
open-inet-socket = yes|no
To control smpppd via the network, this option must be set to yes. The port on
which smpppd listens is 3185. If this parameter is set to yes, the parameters
bind-address, host-range, and password should also be set accordingly.
bind-address = ip
If a host has several IP addresses, use this parameter to determine at which IP address
smpppd should accept connections.
Basic Networking
585
host-range = min ip max ip
The parameter host-range defines a network range. Hosts whose IP addresses
are within this range are granted access to smpppd. All hosts not within this range
are denied access.
password = password
By assigning a password, limit the clients to authorized hosts. As this is a plain-text
password, you should not overrate the security it provides. If no password is assigned,
all clients are permitted to access smpppd.
slp-register = yes|no
With this parameter, the smpppd service can be announced in the network via SLP.
More information about smpppd is available in the smpppd(8) and
smpppd.conf(5) man pages.
38.6.2 Configuring KInternet, cinternet,
and qinternet for Remote Use
KInternet, cinternet, and qinternet can be used to control a local or remote smpppd.
cinternet is the command-line counterpart of the graphical KInternet. qinternet is basicallly the same as KInternet, but does not use the KDE libraries, so it can be used
without KDE and must be installed separately. To prepare these utilities for use with a
remote smpppd, edit the configuration file /etc/smpppd-c.conf manually or using
KInternet. This file only uses three options:
sites = list of sites
Here, tell the front-ends where to search for smpppd. The front-ends test the options
in the order specified here. The local option orders the establishment of a connection to the local smpppd. gateway points to an smpppd on the gateway. The connection should be established as specified under server in config-file. slp
orders the front-ends to connect to an smpppd found via SLP.
server = server
Here, specify the host on which smpppd runs.
password = password
Insert the password selected for smpppd.
586
If smpppd is active, you can now try to access it, for example, with cinternet
--verbose --interface-list. If you experience difficulties at this point, refer
to the smpppd-c.conf(5) and cinternet(8) man pages.
Basic Networking
587
SLP Services in the Network
39
The service location protocol (SLP) was developed to simplify the configuration of
networked clients within a local network. To configure a network client, including all
required services, the administrator traditionally needs detailed knowledge of the servers
available in the network. SLP makes the availability of selected services known to all
clients in the local network. Applications that support SLP can use the information
distributed and be configured automatically.
SUSE Linux supports installation using installation sources provided with SLP and
contains many system services with integrated support for SLP. YaST and Konqueror
both have appropriate front-ends for SLP. You can use SLP to provide networked clients
with central functions, such as an installation server, YOU server, file server, or print
server on your SUSE Linux.
39.1
Registering Your Own Services
Many applications under SUSE Linux already have integrated SLP support through the
use of the libslp library. If a service has not been compiled with SLP support, use
one of the following methods to make it available with SLP:
Static Registration with /etc/slp.reg.d
Create a separate registration file for each new service. The following is an example
of a file for registering a scanner service:
## Register a saned service on this system
## en means english language
## 65535 disables the timeout, so the service registration does
SLP Services in the Network
589
## not need refreshes
service:scanner.sane://$HOSTNAME:6566,en,65535
watch-port-tcp=6566
description=SANE scanner daemon
The most important line in this file is the service URL, which begins with
service:. This contains the service type (scanner.sane) and the address
under which the service is available on the server. $HOSTNAME is automatically
replaced with the full hostname. The name of the TCP port on which the relevant
service can be found follows, separated by a colon. Then enter the language in which
the service should appear and the duration of registration in seconds. These should
be separated from the service URL by commas. Set the value for the duration of
registration between 0 and 65535. 0 prevents registration. 65535 removes all
restrictions.
The registration file also contains the two variables watch-tcp-port and
description. watch-tcp-port links the SLP service announcement to
whether the relevant service is active by having slpd check the status of the service.
The second variable contains a more precise description of the service that is displayed in suitable browsers.
Static Registration with /etc/slp.reg
The only difference from the procedure with /etc/slp.reg.d is the grouping
of all services within a central file.
Dynamic Registration with slptool
If a service should be registered for SLP from proprietary scripts, use the slptool
command line front-end.
39.2
SLP Front-Ends in SUSE Linux
SUSE Linux contains several front-ends that enable SLP information to be checked
and used by means of a network:
slptool
slptool is a simple command line program that can be used to announce SLP inquiries
in the network or announce proprietary services. slptool --help lists all
available options and functions. slptool can also be called from scripts that process
SLP information.
590
YaST SLP Browser
YaST contains a separate SLP browser that lists all services in the local network
announced by SLP in a tree diagram under Network Services → SLP Browser.
Konqueror
When used as a network browser, Konqueror can display all SLP services available
in the local network at slp:/. Click the icons in the main window to obtain more
detailed information about the relevant service. If you use Konqueror with
service:/, click the relevant icon once in the browser window to set up a connection with the selected service.
39.3
Activating SLP
slpd must run on your system if you want to offer services. It is not necessary to start
this daemon simply to make service inquiries. Like most system services in SUSE
Linux, the slpd daemon is controlled by means of a separate init script. The daemon is
inactive by default. To activate it for the duration of a session, run rcslpd start
as root to start it and rcslpd stop to stop it. Perform a restart or status check with
restart or status. If slpd should be active by default, run the insserv slpd
command once as root. This automatically includes slpd in the set of services to start
when a system boots.
39.4
For More Information
The following sources provide further information about SLP:
RFC 2608, 2609, 2610
RFC 2608 generally deals with the definition of SLP. RFC 2609 deals with the
syntax of the service URLs used in greater detail and RFC 2610 deals with DHCP
via SLP.
http://www.openslp.com
The home page of the OpenSLP project.
/usr/share/doc/packages/openslp
This directory contains all available documentation for SLP, including a README
.SuSE containing the SUSE Linux details, the RFCs mentioned above, and two
SLP Services in the Network
591
introductory HTML documents. Programmers who want to use the SLP functions
should install the openslp-devel package to consult its supplied Programmers
Guide.
592
The Domain Name System
40
DNS (domain name system) is needed to resolve the domain names and hostnames into
IP addresses. In this way, the IP address 192.168.0.0 is assigned to the hostname earth,
for example. Before setting up your own name server, read the general information
about DNS in Section 38.3, “Name Resolution” (page 562). The following configuration
examples refer to BIND.
40.1
DNS Basics
40.2
Configuration with YaST
You can use the DNS module of YaST to configure a DNS server for your local network.
When starting the module for the first time, a wizard starts, prompting you to make just
a few basic decisions concerning administration of the server. Completing this initial
setup produces a very basic server configuration that should be functioning in its essential
aspects. The expert mode can be used to deal with more advanced configuration tasks.
40.2.1 Wizard Configuration
The wizard consists of three steps or dialogs. At the appropriate places in the dialogs,
you are given the opportunity to enter the expert configuration mode.
The Domain Name System
593
Forwarder Settings
When starting the module for the first time, see the dialog shown in Figure 40.1,
“DNS Server Installation: Forwarder Settings” (page 594). In it, decide whether the
PPP daemon should provide a list of forwarders on dial-up via DSL or ISDN (PPP
Daemon Sets Forwarders) or whether you want to supply your own list (Set Forwarders Manually).
Figure 40.1
DNS Server Installation: Forwarder Settings
DNS Zones
This dialog consists of several parts and is responsible for the management of zone
files, described in Section 40.5, “Zone Files” (page 607). For a new zone, provide
a name for it in Zone Name. To add a reverse zone, the name must end in
.in-addr.arpa. Finally, select the Zone Type (master or slave). See Figure 40.2,
“DNS Server Installation: DNS Zones” (page 595). Click Edit Zone to configure
other settings of an existing zone. To remove a zone, click Delete Zone.
594
Figure 40.2
DNS Server Installation: DNS Zones
Finish Wizard
In the final dialog, you can open the ports for the DNS service in the firewall that
is activated during the installation and decide whether DNS should be started. The
expert configuration can also be accessed from this dialog. See Figure 40.3, “DNS
Server Installation: Finish Wizard” (page 596).
The Domain Name System
595
Figure 40.3
DNS Server Installation: Finish Wizard
40.2.2 Expert Configuration
After starting the module, YaST opens a window displaying several configuration options. Completing it results in a DNS server configuration with the basic functions in
place:
Start-Up
Under Booting, define whether the DNS server should be started when the system
boots (during booting the system) or manually. To start the DNS server immediately,
select Start DNS Server Now. To stop the DNS server, select Stop DNS Server Now.
To save the current settings, select Save Settings and Restart DNS Server Now. You
can open the DNS port in the firewall with Open Port in Firewall and modify the
firewall settings with Firewall Details.
Forwarders
This is the same dialog as the one opened after starting the wizard configuration
(see Forwarder Settings (page 594)).
Logging
This section allows you to set what the DNS server should log and how. Under Log
Type, specify where the DNS server should write the log data. Use the systemwide
596
log file /var/log/messages by selecting Log to System Log or specify a different file by selecting Log to File. In the latter case, additionally specify the maximum
file size in megabytes and the number of log files to store.
Further options are available under Additional Logging. Enabling Log All DNS
Queries causes every query to be logged, in which case the log file could grow extremely large. For this reason, it is not a good idea to enable this option for other
than debugging purposes. To log the data traffic during zone updates between DHCP
and DNS server, enable Log Zone Updates. To log the data traffic during a zone
transfer from master to slave, enable Log Zone Transfer. See Figure 40.4, “DNS
Server: Logging” (page 597).
Figure 40.4
DNS Server: Logging
DNS Zones
This dialog is explained for the wizard configuration. See Section 40.2.1, “Wizard
Configuration” (page 593).
Slave Zone Editor
This dialog opens if you selected the zone type Slave in the step described in DNS
Zones (page 597). Under Master DNS Server, specify the master from which the
slave should fetch its data. To limit access to the server, select one of the ACLs
from the list. See Figure 40.5, “DNS Server: Slave Zone Editor” (page 598).
The Domain Name System
597
Figure 40.5
DNS Server: Slave Zone Editor
Master Zone Editor
This dialog opens if you selected the zone type Master in the step described in DNS
Zones (page 597). The dialog comprises several pages: Basic (the one opened first),
NS Records, MX Records, SOA, and Records.
Zone Editor (NS Records)
This dialog allows you to define alternative name servers for the zones specified.
Make sure that your own name server is included in the list. To add a record, enter
its name under Name Server to Add then confirm with Add. See Figure 40.6, “DNS
Server: Zone Editor (NS Records)” (page 599).
598
Figure 40.6
DNS Server: Zone Editor (NS Records)
Zone Editor (MX Records)
To add a mail server for the current zone to the existing list, enter the corresponding
address and priority value. After doing so, confirm by selecting Add. See Figure 40.7,
“DNS Server: Zone Editor (MX Records)” (page 600).
The Domain Name System
599
Figure 40.7
DNS Server: Zone Editor (MX Records)
Zone Editor (SOA)
This page allows you to create SOA (start of authority) records. For an explanation
of the individual options, refer to Example 40.6, “File /var/lib/named/world.zone”
(page 608).
600
Figure 40.8
DNS Server: Zone Editor (SOA)
Zone Editor (Records)
This dialog manages name resolution. In Record Key, enter the hostname then select
its type. A-Record represents the main entry. The value for this should be an IP address. CNAME is an alias. Use the types NS and MX for detailed or partial records
that expand on the information provided in the NS Records and MX Records tabs.
These three types resolve to an existing A record. PTR is for reverse zones. It is the
opposite of an A record.
40.3
Starting the Name Server BIND
On a SUSE Linux system, the name server BIND (Berkeley Internet name domain)
comes preconfigured so it can be started right after installation without any problem.
If you already have a functioning Internet connection and have entered 127.0.0.1
as the name server address for localhost in /etc/resolv.conf, you normally
already have a working name resolution without needing to know the DNS of the
provider. BIND carries out name resolution via the root name server, a notably slower
process. Normally, the DNS of the provider should be entered with its IP address in the
configuration file /etc/named.conf under forwarders to ensure effective and
secure name resolution. If this works so far, the name server runs as a pure cachingonly name server. Only when you configure its own zones will it become a proper DNS.
The Domain Name System
601
A simple example of this is included in the documentation in /usr/share/doc/
packages/bind/sample-config.
TIP: Automatic Adaptation of the Name Server Information
Depending on the type of Internet connection or the network connection, the
name server information can automatically be adapted to the current conditions.
To do this, set the variable MODIFY_NAMED_CONF_DYNAMICALLY in the file
/etc/sysconfig/network/config to yes.
However, do not set up any official domains until assigned one by the responsible institution. Even if you have your own domain and it is managed by the provider, you are
better off not using it, because BIND would otherwise not forward requests for this
domain. The Web server at the provider, for example, would not be accessible for this
domain.
To start the name server, enter the command rcnamed start as root. If “done”
appears to the right in green, named, as the name server process is called, has been
started successfully. Test the name server immediately on the local system with the
host or dig programs, which should return localhost as the default server with
the address 127.0.0.1. If this is not the case, /etc/resolv.conf probably
contains an incorrect name server entry or the file does not exist at all. For the first test,
enter host 127.0.0.1, which should always work. If you get an error message, use
rcnamed status to see whether the server is actually running. If the name server
does not start or behaves unexpectedly, you can usually find the cause in the log file
/var/log/messages.
To use the name server of the provider or one already running on your network as the
forwarder, enter the corresponding IP address or addresses in the options section
under forwarders. The addresses included in Example 40.1, “Forwarding Options
in named.conf” (page 602) are just examples. Adjust these entries to your own setup.
Example 40.1
Forwarding Options in named.conf
options {
directory "/var/lib/named";
forwarders { 10.11.12.13; 10.11.12.14; };
listen-on { 127.0.0.1; 192.168.0.99; };
allow-query { 127/8; 192.168.0/24; };
notify no;
};
602
The options entry is followed by entries for the zone, localhost, and
0.0.127.in-addr.arpa. The type hint entry under “.” should always be
present. The corresponding files do not need to be modified and should work as they
are. Also make sure that each entry is closed with a “;” and that the curly braces are in
the correct places. After changing the configuration file /etc/named.conf or the
zone files, tell BIND to reread them with rcnamed reload. Achieve the same by
stopping and restarting the name server with rcnamed restart. Stop the server at
any time by entering rcnamed stop.
40.4
The Configuration File
/etc/named.conf
All the settings for the BIND name server itself are stored in the file /etc/named
.conf. However, the zone data for the domains to handle, consisting of the hostnames,
IP addresses, and so on, are stored in separate files in the /var/lib/named directory.
The details of this are described later.
/etc/named.conf is roughly divided into two areas. One is the options section
for general settings and the other consists of zone entries for the individual domains.
A logging section and acl (access control list) entries are optional. Comment lines
begin with a # sign or //. A minimal /etc/named.conf is shown in Example 40.2,
“A Basic /etc/named.conf” (page 604).
The Domain Name System
603
Example 40.2
A Basic /etc/named.conf
options {
directory "/var/lib/named";
forwarders { 10.0.0.1; };
notify no;
};
zone "localhost" in {
type master;
file "localhost.zone";
};
zone "0.0.127.in-addr.arpa" in {
type master;
file "127.0.0.zone";
};
zone "." in {
type hint;
file "root.hint";
};
40.4.1 Important Configuration Options
directory "filename";
Specifies the directory in which BIND can find the files containing the zone data.
Usually, this is /var/lib/named.
forwarders { ip-address; };
Specifies the name servers (mostly of the provider) to which DNS requests should
be forwarded if they cannot be resolved directly. Replace ip-address with an
IP address like 10.0.0.1.
forward first;
Causes DNS requests to be forwarded before an attempt is made to resolve them
via the root name servers. Instead of forward first, forward only can be
written to have all requests forwarded and none sent to the root name servers. This
makes sense for firewall configurations.
listen-on port 53 { 127.0.0.1; ip-address; };
Tells BIND on which network interfaces and port to accept client queries. port
53 does not need to be specified explicitly, because 53 is the default port. Enter
604
127.0.0.1 to permit requests from the local host. If you omit this entry entirely,
all interfaces are used by default.
listen-on-v6 port 53 {any; };
Tells BIND on which port it should listen for IPv6 client requests. The only alternative to any is none. As far as IPv6 is concerned, the server only accepts a wild
card address.
query-source address * port 53;
This entry is necessary if a firewall is blocking outgoing DNS requests. This tells
BIND to post requests externally from port 53 and not from any of the high ports
above 1024.
query-source-v6 address * port 53;
Tells BIND which port to use for IPv6 queries.
allow-query { 127.0.0.1; net; };
Defines the networks from which clients can post DNS requests. Replace net with
address information like 192.168.1/24. The /24 at the end is an abbreviated
expression for the netmask, in this case, 255.255.255.0.
allow-transfer ! *;;
Controls which hosts can request zone transfers. In the example, such requests are
completely denied with ! *. Without this entry, zone transfers can be requested
from anywhere without restrictions.
statistics-interval 0;
In the absence of this entry, BIND generates several lines of statistical information
per hour in /var/log/messages. Set it to 0 to suppress these statistics completely or set an interval in minutes.
cleaning-interval 720;
This option defines at which time intervals BIND clears its cache. This triggers an
entry in /var/log/messages each time it occurs. The time specification is in
minutes. The default is 60 minutes.
interface-interval 0;
BIND regularly searches the network interfaces for new or nonexisting interfaces.
If this value is set to 0, this is not done and BIND only listens at the interfaces detected at start-up. Otherwise, the interval can be defined in minutes. The default is
sixty minutes.
The Domain Name System
605
notify no;
no prevents other name servers from being informed when changes are made to
the zone data or when the name server is restarted.
40.4.2 Logging
What, how, and where logging takes place can be extensively configured in BIND.
Normally, the default settings should be sufficient. Example 40.3, “Entry to Disable
Logging” (page 606) shows the simplest form of such an entry and completely suppresses
any logging.
Example 40.3
Entry to Disable Logging
logging {
category default { null; };
};
40.4.3 Zone Entries
Example 40.4
Zone Entry for my-domain.de
zone "my-domain.de" in {
type master;
file "my-domain.zone";
notify no;
};
After zone, specify the name of the domain to administer (my-domain.de) followed
by in and a block of relevant options enclosed in curly braces, as shown in Example 40.4, “Zone Entry for my-domain.de” (page 606). To define a slave zone, switch the
type to slave and specify a name server that administers this zone as master
(which, in turn, may be a slave of another master), as shown in Example 40.5, “Zone
Entry for other-domain.de” (page 606).
Example 40.5
Zone Entry for other-domain.de
zone "other-domain.de" in {
type slave;
file "slave/other-domain.zone";
masters { 10.0.0.1; };
};
The zone options:
606
type master;
By specifying master, tell BIND that the zone is handled by the local name server.
This assumes that a zone file has been created in the correct format.
type slave;
This zone is transferred from another name server. It must be used together with
masters.
type hint;
The zone . of the hint type is used to set the root name servers. This zone definition
can be left as is.
file my-domain.zone or file “slave/other-domain.zone”;
This entry specifies the file where zone data for the domain is located. This file is
not required for a slave, because this data is fetched from another name server. To
differentiate master and slave files, use the directory slave for the slave files.
masters { server-ip-address; };
This entry is only needed for slave zones. It specifies from which name server the
zone file should be transferred.
allow-update {! *; };
This option controls external write access, which would allow clients to make a
DNS entry—something not normally desirable for security reasons. Without this
entry, zone updates are not allowed at all. The above entry achieves the same because
! * effectively bans any such activity.
40.5
Zone Files
Two types of zone files are needed. One assigns IP addresses to hostnames and the
other does the reverse: it supplies a hostname for an IP address.
TIP: Using the Dot in Zone Files
The . has an important meaning in the zone files. If hostnames are given
without a final ., the zone is appended. Complete hostnames specified with a
full domain name must end with a . to avoid having the domain added to it
The Domain Name System
607
again. A missing or wrongly placed dot is probably the most frequent cause of
name server configuration errors.
The first case to consider is the zone file world.zone, responsible for the domain
world.cosmos, shown in Example 40.6, “File /var/lib/named/world.zone” (page 608).
Example 40.6
File /var/lib/named/world.zone
$TTL 2D
world.cosmos. IN SOA
2003072441
1D
2H
1W
2D )
gateway
sun
moon
earth
mars
www
;
;
;
;
;
gateway
serial
refresh
retry
expiry
minimum
IN NS
IN MX
gateway
10 sun
IN
IN
IN
IN
IN
IN
IN
192.168.0.1
192.168.1.1
192.168.0.2
192.168.0.3
192.168.1.2
192.168.1.3
moon
root.world.cosmos. (
A
A
A
A
A
A
CNAME
Line 1:
$TTL defines the default time to live that should apply to all the entries in this file.
In this example, entries are valid for a period of two days (2 D).
Line 2:
This is where the SOA (start of authority) control record begins:
• The name of the domain to administer is world.cosmos in the first position.
This ends with a ., because otherwise the zone would be appended a second time.
Alternatively, @ can be entered here, in which case the zone would be extracted
from the corresponding entry in /etc/named.conf.
• After IN SOA is the name of the name server in charge as master for this zone.
The name is expanded from gateway to gateway.world.cosmos, because
it does not end with a ..
• An e-mail address of the person in charge of this name server follows. Because
the @ sign already has a special meaning, . is entered here instead. For
608
[email protected] the entry must read root.world.cosmos.. The .
must be included at the end to prevent the zone from being added.
• The ( includes all lines up to ) into the SOA record.
Line 3:
The serial number is an arbitrary number that is increased each time this file
is changed. It is needed to inform the secondary name servers (slave servers) of
changes. For this, a 10 digit number of the date and run number, written as
YYYYMMDDNN, has become the customary format.
Line 4:
The refresh rate specifies the time interval at which the secondary name
servers verify the zone serial number. In this case, one day.
Line 5:
The retry rate specifies the time interval at which a secondary name server,
in case of error, attempts to contact the primary server again. Here, two hours.
Line 6:
The expiration time specifies the time frame after which a secondary name
server discards the cached data if it has not regained contact to the primary server.
Here, it is a week.
Line 7:
The last entry in the SOA record specifies the negative caching TTL—the
time for which results of unresolved DNS queries from other servers may be cached.
Line 9:
The IN NS specifies the name server responsible for this domain. gateway is
extended to gateway.world.cosmos because it does not end with a .. There
can be several lines like this—one for the primary and one for each secondary name
server. If notify is not set to no in /etc/named.conf, all the name servers
listed here are informed of the changes made to the zone data.
Line 10:
The MX record specifies the mail server that accepts, processes, and forwards emails for the domain world.cosmos. In this example, this is the host
sun.world.cosmos. The number in front of the hostname is the preference
value. If there are multiple MX entries, the mail server with the smallest value is
The Domain Name System
609
taken first and, if mail delivery to this server fails, an attempt is made with the next
higher value.
Lines 12–17:
These are the actual address records where one or more IP addresses are assigned
to hostnames. The names are listed here without a . because they do not include
their domain, so world.cosmos is added to all of them. Two IP addresses are
assigned to the host gateway, because it has two network cards. Wherever the
host address is a traditional one (IPv4), the record is marked with A. If the address
is an IPv6 address, the entry is marked with A6. The previous token for IPv6 addresses was AAAA, which is now obsolete.
Line 18:
The alias www can be used to address mond (CNAME means canonical name).
The pseudodomain in-addr.arpa is used for the reverse lookup of IP addresses
into hostnames. It is appended to the network part of the address in reverse notation.
So 192.168.1 is resolved into 1.168.192.in-addr.arpa. See Example 40.7,
“Reverse Lookup” (page 610).
Example 40.7
Reverse Lookup
$TTL 2D
1.168.192.in-addr.arpa. IN SOA gateway.world.cosmos. root.world.cosmos. (
2003072441
; serial
1D
; refresh
2H
; retry
1W
; expiry
2D )
; minimum
1
2
3
IN NS
gateway.world.cosmos.
IN PTR
IN PTR
IN PTR
gateway.world.cosmos.
earth.world.cosmos.
mars.world.cosmos.
Line 1:
$TTL defines the standard TTL that applies to all entries here.
Line 2:
The configuration file should activate reverse lookup for the network
192.168.1.0. Given that the zone is called 1.168.192.in-addr.arpa,
should not be added to the hostnames. Therefore, all hostnames are entered in their
610
complete form—with their domain and with a . at the end. The remaining entries
correspond to those described for the previous world.cosmos example.
Lines 3–7:
See the previous example for world.cosmos.
Line 9:
Again this line specifies the name server responsible for this zone. This time, however, the name is entered in its complete form with the domain and a . at the end.
Lines 11–13:
These are the pointer records hinting at the IP addresses on the respective hosts.
Only the last part of the IP address is entered at the beginning of the line, without
the . at the end. Appending the zone to this (without the .in-addr.arpa) results
in the complete IP address in reverse order.
Normally, zone transfers between different versions of BIND should be possible without
any problem.
40.6
Dynamic Update of Zone Data
The term dynamic update refers to operations by which entries in the zone files of a
master server are added, changed, or deleted. This mechanism is described in RFC 2136.
Dynamic update is configured individually for each zone entry by adding an optional
allow-update or update-policy rule. Zones to update dynamically should not
be edited by hand.
Transmit the entries to update to the server with the command nsupdate. For the
exact syntax of this command, check the manual page for nsupdate (man 8 nsupdate).
For security reasons, any such update should be performed using TSIG keys as described
in Section 40.7, “Secure Transactions” (page 611).
40.7
Secure Transactions
Secure transactions can be made with the help of transaction signatures (TSIGs) based
on shared secret keys (also called TSIG keys). This section describes how to generate
and use such keys.
The Domain Name System
611
Secure transactions are needed for communication between different servers and for
the dynamic update of zone data. Making the access control dependent on keys is much
more secure than merely relying on IP addresses.
Generate a TSIG key with the following command (for details, see
man dnssec-keygen):
dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2
This creates two files with names similar to these:
Khost1-host2.+157+34265.private Khost1-host2.+157+34265.key
The key itself (a string like ejIkuCyyGJwwuN3xAteKgg==) is found in both files.
To use it for transactions, the second file (Khost1-host2.+157+34265.key)
must be transferred to the remote host, preferably in a secure way (using scp, for example). On the remote server, the key must be included in the file /etc/named.conf
to enable a secure communication between host1 and host2:
key host1-host2. {
algorithm hmac-md5;
secret ";ejIkuCyyGJwwuN3xAteKgg==;
};
WARNING: File Permissions of /etc/named.conf
Make sure that the permissions of /etc/named.conf are properly restricted.
The default for this file is 0640, with the owner being root and the group
named. As an alternative, move the keys to an extra file with specially limited
permissions, which is then included from /etc/named.conf.
To enable the server host1 to use the key for host2 (which has the address
192.168.2.3 in this example), the server's /etc/named.conf must include the
following rule:
server 192.168.2.3 {
keys { host1-host2. ;};
};
Analogous entries must be included in the configuration files of host2.
Add TSIG keys for any ACLs (access control lists, not to be confused with file system
ACLs) that are defined for IP addresses and address ranges to enable transaction security. The corresponding entry could look like this:
612
allow-update { key host1-host2. ;};
This topic is discussed in more detail in the BIND Administrator Reference Manual
under update-policy.
40.8
DNS Security
DNSSEC, or DNS security, is described in RFC 2535. The tools available for DNSSEC
are discussed in the BIND Manual.
A zone considered secure must have one or several zone keys associated with it. These
are generated with dnssec-keygen, just like the host keys. The DSA encryption
algorithm is currently used to generate these keys. The public keys generated should
be included in the corresponding zone file with an $INCLUDE rule.
With the command dnssec-makekeyset, all keys generated are packaged into one
set, which must then be transferred to the parent zone in a secure manner. On the parent,
the set is signed with dnssec-signkey. The files generated by this command are
then used to sign the zones with dnssec-signzone, which in turn generates the
files to include for each zone in /etc/named.conf.
40.9
For More Information
For additional information, refer to the BIND Administrator Reference Manual, which
is installed under /usr/share/doc/packages/bind/. Consider additionally
consulting the RFCs referenced by the manual and the manual pages included with
BIND. /usr/share/doc/packages/bind/README.SuSE contains up-to-date
information about BIND in SUSE Linux.
The Domain Name System
613
41
Using NIS
As soon as multiple UNIX systems in a network want to access common resources, it
becomes important that all user and group identities are the same for all machines in
that network. The network should be transparent to users: whatever machines they use,
they always find themselves in exactly the same environment. This is made possible
by means of NIS and NFS services. NFS distributes file systems over a network and is
discussed in Chapter 42, Sharing File Systems with NFS (page 623).
NIS (Network Information Service) can be described as a database-like service that
provides access to the contents of /etc/passwd, /etc/shadow, and /etc/group
across networks. NIS can also be used for other purposes (making the contents of files
like /etc/hosts or /etc/services available, for example), but this is beyond
the scope of this introduction. People often refer to NIS as YP, because it works like
the network's “yellow pages.”
41.1
Configuring NIS Servers Using
YaST
For configuration, select Network Services → NIS Server from the YaST control center.
If there is no NIS server yet in your network, activate Install and set up a NIS Master
Server in the next screen. YaST immediately installs the required packages.
If you have already installed NIS software, click Create NIS Master Server. If you already have an NIS server (a master), you can add a NIS slave server (for example, if
you want to configure a new subnetwork). First, the configuration of the master server
Using NIS
615
is described. Clicking Do nothing and leave setup takes you back to the YaST Control
Center with no saved changes.
Figure 41.1
NIS Server Setup
After all packages have been installed, enter the NIS domain name at the top of the
configuration dialog, which is shown in Figure 41.2, “Master Server Setup” (page 617).
With the check box, define whether the host should also be a NIS client, enabling users
to log in and access data from the NIS server. Check the boxes to apply, including the
Changing of paswords option. Further options can be set by clicking Other global settings. Here, access a screen in which you can change the source directory, merge passwords, and set minimum user and group IDs. Click OK to return to the main dialog.
Click Next to continue with configuration.
616
Figure 41.2
Master Server Setup
In the next screen, specify which maps should be made available. Clicking Next takes
you to the following screen in which you determine which hosts are allowed to query
the NIS server. You can add, delete, and edit hosts. Click Finish to save changes and
exit the configuration dialog.
Using NIS
617
Figure 41.3
NIS Server Maps Setup
To configure additional NIS slave servers in your network, activate Install and set up
a NIS Slave Server now. If NIS software has already been installed, click Create NIS
Slave Server and click Next to continue. In the next screen, enter the NIS domain name
and check the boxes that apply.
To allow users in your network (both local users and those managed through the NIS
server) to change their passwords on the NIS server (with the command yppasswd),
activate the corresponding option. This makes the options Allow Changes to GECOS
Field and Allow Changes to Login Shell available. “GECOS” means that the users can
also change their names and address settings with the command ypchfn. “SHELL”
allows users to change their default shell with the command ypchsh, for example, to
switch from bash to sh.
Further options can be set by clicking Other global settings. Here, access a screen,
shown in Figure 41.4, “Changing the Directory and Synchronizing Files for a NIS
Server” (page 619), in which to change the source directory of the NIS server (/etc
by default). In addition, passwords and groups can be merged here. The setting should
be Yes so the files (/etc/passwd, /etc/shadow, and /etc/group) can be
synchronized. Also determine the smallest user and group ID. Click OK to confirm
your settings and return to the previous screen.
618
After your settings have been made, advance to the next screen by clicking Next. In the
next dialog, check which maps should be available then click Next to continue. In the
final screen, enter which hosts are allowed to query the NIS server. You can add, edit,
or delete hosts by clicking the appropriate buttons. Click Finish to save changes and
exit setup. Then click Next.
Figure 41.4
Changing the Directory and Synchronizing Files for a NIS Server
If you previously enabled Active Slave NIS Server Exists, enter the hostnames used as
slaves and click Next. If you do not use slave servers, the slave configuration is skipped
and you continue directly to the dialog for the database configuration. Here, specify
the maps, the partial databases to transfer from the NIS server to the client. The default
settings are usually adequate.
Next continues to the last dialog, shown in Figure 41.5, “Setting Request Permissions
for a NIS Server” (page 620). Specify from which networks requests can be sent to the
NIS server. Normally, this is your internal network. In this case, there should be the
following two entries:
255.0.0.0
0.0.0.0
127.0.0.0
0.0.0.0
Using NIS
619
The first entry enables connections from your own host, which is the NIS server. The
second one allows all hosts with access to the same network to send requests to the
server.
Figure 41.5
Setting Request Permissions for a NIS Server
IMPORTANT: Automatic Firewall Configuration
If a firewall is active on your system (SuSEfirewall2), YaST adapts its configuration
for the NIS server by enabling the portmap service when Open Ports in Firewall
is selected.
41.2
Configuring NIS Clients
Use this module to configure a NIS client. After you choose to use NIS and, depending
on the circumstances, the automounter, this dialog opens. Select whether the host has
a static IP address or receives one issued by DHCP. DHCP also provides the NIS domain
and the NIS server. For information about DHCP, see Chapter 43, DHCP (page 629).
If a static IP address is used, specify the NIS domain and the NIS server manually. See
Figure 41.6, “Setting Domain and Address of a NIS Server” (page 621). Find makes
620
YaST search for an active NIS server in your network. Broadcast enables searching in
the local network to find a server after the specified servers fail to respond.
You can also specify multiple servers by entering their addresses in Addresses of NIS
servers and separating them by spaces.
In the expert settings, disable Answer Remote Hosts if you do not want other hosts to
be able to query which server your client is using. By checking Broken Server, the client
is enabled to receive replies from a server communicating through an unprivileged port.
For further information, see man ypbind.
After you have made your settings, click Finish to save them and return to the YaST
control center.
Figure 41.6
Setting Domain and Address of a NIS Server
Using NIS
621
Sharing File Systems with NFS
42
As mentioned in Chapter 41, Using NIS (page 615), NFS works with NIS to make a
network transparent to the user. With NFS, it is possible to distribute file systems over
the network. It does not matter at which terminal users are logged in. They always find
themselves in the same environment.
Like NIS, NFS is a client/server system. A machine can be both—it can supply file
systems over the network (export) and mount file systems from other hosts (import).
IMPORTANT: Need for DNS
In principle, all exports can be made using IP addresses only. To avoid timeouts, however, you should have a working DNS system. This is necessary at
least for logging purposes, because the mountd daemon does reverse lookups.
42.1
Importing File Systems with
YaST
Users authorized to do so can mount NFS directories from an NFS server into their
own file trees. This can be achieved most easily using the YaST module NFS Client.
Just enter the hostname of the NFS server, the directory to import, and the mount point
at which to mount this directory locally. All this is done after Add is clicked in the first
dialog. Click Open Port in Firewall to open the firewall to allow access to the service
from remote computers. The firewall status is displayed next to the check box. Clicking
Sharing File Systems with NFS
623
OK saves your changes. See Figure 42.1, “NFS Client Configuration with YaST”
(page 624).
Figure 42.1
42.2
NFS Client Configuration with YaST
Importing File Systems
Manually
File systems can easily be imported manually from an NFS server. The only prerequisite
is a running RPC port mapper, which can be started by entering the command
rcportmap start as root. Once this prerequisite is met, remote file systems exported on the respective machines can be mounted in the file system just like local hard
disks using the command mount with the following syntax:
mount host:remote-path local-path
If user directories from the machine sun, for example, should be imported, use the following command:
mount sun:/home /home
624
42.3
Exporting File Systems with
YaST
With YaST, turn a host in your network into an NFS server—a server that exports directories and files to all hosts granted access to it. This could be done to provide applications to all members of a group without installing them locally on each and every
host. To install such a server, start YaST and select Network Services → NFS Server.
A dialog like that in Figure 42.2, “NFS Server Configuration Tool” (page 625) opens.
Figure 42.2
NFS Server Configuration Tool
Next, activate Start NFS Server and click Next. In the upper text field, enter the directories to export. Below, enter the hosts that should have access to them. This dialog is
shown in Figure 42.3, “Configuring an NFS Server with YaST” (page 626). There are
four options that can be set for each host: single host, netgroups, wildcards,
and IP networks. A more thorough explanation of these options is provided by
man exports. Exit completes the configuration.
Sharing File Systems with NFS
625
Figure 42.3
Configuring an NFS Server with YaST
IMPORTANT: Automatic Firewall Configuration
If a firewall is active on your system (SuSEfirewall2), YaST adapts its configuration
for the NFS server by enabling the nfs service when Open Ports in Firewall is
selected.
42.4
Exporting File Systems
Manually
If you do not want to use YaST, make sure the following systems run on the NFS
server:
• RPC portmapper (portmap)
• RPC mount daemon (rpc.mountd)
• RPC NFS daemon (rpc.nfsd)
626
For these services to be started by the scripts /etc/init.d/portmap and
/etc/init.d/nfsserver when the system is booted, enter the commands
insserv /etc/init.d/nfsserver and insserv /etc/init.d/portmap.
Also define which file systems should be exported to which host in the configuration
file /etc/exports.
For each directory to export, one line is needed to set which machines may access that
directory with what permissions. All subdirectories of this directory are automatically
exported as well. Authorized machines are usually specified with their full names (including domain name), but it is possible to use wild cards like * or ? (which expand
the same way as in the Bash shell). If no machine is specified here, any machine is allowed to import this file system with the given permissions.
Set permissions for the file system to export in brackets after the machine name. The
most important options are shown in Table 42.1, “Permissions for Exported File System”
(page 627).
Table 42.1
Permissions for Exported File System
option
meaning
ro
The file system is exported with read-only permission (default).
rw
The file system is exported with read-write permission.
root_squash
This ensures that the user root of an importing machine
does not have root permissions on this file system. This is
achieved by assigning user ID 65534 to users with user ID
0 (root). This user ID should be set to nobody (which is
the default).
no_root_squash
Does not assign user ID 0 to user ID 65534, keeping the
root permissions valid.
link_relative
Converts absolute links (those beginning with /) to a sequence of ../. This is only useful if the entire file system
of a machine is mounted (default).
Sharing File Systems with NFS
627
option
meaning
link_absolute
Symbolic links remain untouched.
map_identity
User IDs are exactly the same on both client and server (default).
map_daemon
Client and server do not have matching user IDs. This tells
nfsd to create a conversion table for user IDs. The ugidd
daemon is required for this to work.
Your exports file might look like Example 42.1, “/etc/exports” (page 628). /etc/
exports is read by mountd and nfsd. If you change anything in this file, restart mountd
and nfsd for your changes to take effect. This can easily be done with
rcnfsserver restart.
Example 42.1
#
# /etc/exports
#
/home
/usr/X11
/usr/lib/texmf
/
/home/ftp
# End of exports
628
/etc/exports
sun(rw)
venus(rw)
sun(ro)
venus(ro)
sun(ro)
venus(rw)
earth(ro,root_squash)
(ro)
43
DHCP
The purpose of the dynamic host configuration protocol (DHCP) is to assign network
settings centrally from a server rather than configuring them locally on each and every
workstation. A host configured to use DHCP does not have control over its own static
address. It is enabled to configure itself completely and automatically according to directions from the server.
One way to use DHCP is to identify each client using the hardware address of its network
card (which is fixed in most cases), then supply that client with identical settings each
time it connects to the server. DHCP can also be configured so the server assigns addresses to each interested client dynamically from an address pool set up for that purpose.
In the latter case, the DHCP server tries to assign the same address to the client each
time it receives a request from it, even over longer periods. This, of course, only works
as long as the network does not have more clients than addresses.
With these possibilities, DHCP can make life easier for system administrators in two
ways. Any changes, even bigger ones, related to addresses and the network configuration
in general can be implemented centrally by editing the server's configuration file. This
is much more convenient than reconfiguring numerous workstations. Also it is much
easier to integrate machines, particularly new machines, into the network, because they
can be given an IP address from the pool. Retrieving the appropriate network settings
from a DHCP server can be especially useful in the case of laptops regularly used in
different networks.
A DHCP server supplies not only the IP address and the netmask, but also the hostname,
domain name, gateway, and name server addresses for the client to use. In addition to
that, DHCP allows for a number of other parameters to be configured in a centralized
DHCP
629
way, for example, a time server from which clients may poll the current time or even
a print server.
43.1
Configuring a DHCP Server with
YaST
When the module is started for the first time, a wizard starts, prompting you to make
a few basic decision concerning server administration. Completing this initial setup
produces a very basic server configuration that should function in essential aspects.
The expert mode can be used to deal with more advanced configuration tasks.
Card Selection
In the first step, YaST looks for the network interfaces available on your system
then displays them in a list. From the list, select the interface on which the DHCP
server should listen and click Add then select Open Firewall for Selected Interface
to open the firewall for this interface. See Figure 43.1, “DHCP Server: Card Selection” (page 630).
Figure 43.1
630
DHCP Server: Card Selection
Global Settings
In the entry fields, provide the network specifics for all clients the DHCP server
should manage. These specifics are the domain name, address of a time server, addresses of the primary and secondary name server, addresses of a print and a WINS
server (for a mixed network with both Windows and Linux clients), gateway address,
and lease time. See Figure 43.2, “DHCP Server: Global Settings” (page 631).
Figure 43.2
DHCP Server: Global Settings
Dynamic DHCP
In this step, configure how dynamic IP addresses should be assigned to clients. To
do so, specify an IP range from which the server can assign addresses to DHCP
clients. All these addresses must be covered by the same netmask. Also specify the
lease time during which a client may keep its IP address without needing to request
an extension of the lease. Optionally, specify the maximum lease time—the period
during which the server reserves an IP address for a particular client. See Figure 43.3,
“DHCP Server: Dynamic DHCP” (page 632).
DHCP
631
Figure 43.3
DHCP Server: Dynamic DHCP
Finishing the Configuration and Setting the Start Mode
After the third part of the configuration wizard, a last dialog is shown in which you
can define how the DHCP server should be started. Here, specify whether to start
the DHCP server automatically when the system is booted or manually when
needed (for example, for test purposes). Click Finish to complete the configuration
of the server. See Figure 43.4, “DHCP Server: Start-Up” (page 633).
632
Figure 43.4
43.2
DHCP Server: Start-Up
DHCP Software Packages
Both a DHCP server and DHCP clients are available for SUSE Linux. The DHCP
server available is dhcpd (published by the Internet Software Consortium). On the client
side, choose between two different DHCP client programs: dhclient (also from ISC)
and the DHCP client daemon in the dhcpcd package.
SUSE Linux installs dhcpcd by default. The program is very easy to handle and is
launched automatically on each system boot to watch for a DHCP server. It does not
need a configuration file to do its job and works out of the box in most standard setups.
For more complex situations, use the ISC dhclient, which is controlled by means of the
configuration file /etc/dhclient.conf.
43.3
The DHCP Server dhcpd
The core of any DHCP system is the dynamic host configuration protocol daemon. This
server leases addresses and watches how they are used, according to the settings defined
in the configuration file /etc/dhcpd.conf. By changing the parameters and values
DHCP
633
in this file, a system administrator can influence the program's behavior in numerous
ways. Look at the basic sample /etc/dhcpd.conf file in Example 43.1, “The
Configuration File /etc/dhcpd.conf” (page 634).
Example 43.1
The Configuration File /etc/dhcpd.conf
default-lease-time 600;
max-lease-time 7200;
option
option
option
option
option
# 10 minutes
# 2 hours
domain-name "cosmos.all";
domain-name-servers 192.168.1.1, 192.168.1.2;
broadcast-address 192.168.1.255;
routers 192.168.1.254;
subnet-mask 255.255.255.0;
subnet 192.168.1.0 netmask 255.255.255.0
{
range 192.168.1.10 192.168.1.20;
range 192.168.1.100 192.168.1.200;
}
This simple configuration file should be sufficient to get the DHCP server to assign IP
addresses in the network. Make sure that a semicolon is inserted at the end of each line,
because otherwise dhcpd is not started.
The sample file can be divided into three sections. The first one defines how many
seconds an IP address is leased to a requesting client by default
(default-lease-time) before it should apply for renewal. The section also includes
a statement of the maximum period for which a machine may keep an IP address assigned
by the DHCP server without applying for renewal (max-lease-time).
In the second part, some basic network parameters are defined on a global level:
• The line option domain-name defines the default domain of your network.
• With the entry option domain-name-servers, specify up to three values
for the DNS servers used to resolve IP addresses into hostnames and vice versa.
Ideally, configure a name server on your machine or somewhere else in your network
before setting up DHCP. That name server should also define a hostname for each
dynamic address and vice versa. To learn how to configure your own name server,
read Chapter 40, The Domain Name System (page 593).
• The line option broadcast-address defines the broadcast address the requesting client should use.
634
• With option routers, set where the server should send data packets that
cannot be delivered to a host on the local network (according to the source and
target host address and the subnet mask provided). In most cases, especially in
smaller networks, this router is identical to the Internet gateway.
• With option subnet-mask, specify the netmask assigned to clients.
The last section of the file defines a network, including a subnet mask. To finish,
specify the address range that the DHCP daemon should use to assign IP addresses to
interested clients. In this example, clients may be given any address between
192.168.1.10 and 192.168.1.20 as well as 192.168.1.100 and
192.168.1.200.
After editing these few lines, you should be able to activate the DHCP daemon with
the command rcdhcpd start. It will be ready for use immediately. Use the command
rcdhcpd check-syntax to perform a brief syntax check. If you encounter any
unexpected problems with your configuration—the server aborts with an error or does
not return done on start—you should be able to find out what has gone wrong by
looking for information either in the main system log /var/log/messages or on
console 10 ( Ctrl + Alt + F10 ).
On a default SUSE Linux system, the DHCP daemon is started in a chroot environment
for security reasons. The configuration files must be copied to the chroot environment
so the daemon can find them. Normally, there is no need to worry about this because
the command rcdhcpd start automatically copies the files.
43.3.1 Clients with Fixed IP Addresses
DHCP can also be used to assign a predefined, static address to a specific client for
each request. Addresses assigned explicitly always take priority over dynamic addresses
from the pool. A static address never expires in the way a dynamic address would, for
example, if there were not enough addresses available so the server needed to redistribute
them among clients.
To identify a client configured with a static address, dhcpd uses the hardware address,
which is a globally unique, fixed numerical code consisting of six octet pairs for the
identification of all network devices (for example, 00:00:45:12:EE:F4). If the
respective lines, like the ones in Example 43.2, “Additions to the Configuration File”
(page 636), are added to the configuration file of Example 43.1, “The Configuration
DHCP
635
File /etc/dhcpd.conf” (page 634), the DHCP daemon always assigns the same set of
data to the corresponding client.
Example 43.2
Additions to the Configuration File
host earth {
hardware ethernet 00:00:45:12:EE:F4;
fixed-address 192.168.1.21;
}
The name of the respective client (host hostname, here earth) is entered in the
first line and the MAC address in the second line. On Linux hosts, find this address
with the command ifstatus followed by the network device (for example, eth0).
If necessary, activate the network card first with ifup eth0. The output should contain
something like
link/ether 00:00:45:12:EE:F4
In the preceding example, a client with a network card having the MAC address
00:00:45:12:EE:F4 is assigned the IP address 192.168.1.21 and the hostname
earth automatically. The type of hardware to enter is ethernet in nearly all cases,
although token-ring, which is often found on IBM systems, is also supported.
43.3.2 The SUSE Linux Version
To improve security, the SUSE version of the ISC's DHCP server comes with the nonroot/chroot patch by Ari Edelkind applied. This enables dhcpd to run with the user ID
nobody and run in a chroot environment (/var/lib/dhcp). To make this possible,
the configuration file dhcpd.conf must be located in /var/lib/dhcp/etc. The
init script automatically copies the file to this directory when starting.
Control the server's behavior regarding this feature by means of entries in the file /etc/
sysconfig/dhcpd. To run dhcpd without the chroot environment, set the variable
DHCPD_RUN_CHROOTED in /etc/sysconfig/dhcpd to “no”.
To enable dhcpd to resolve hostnames even from within the chroot environment, some
other configuration files must be copied as well:
• /etc/localtime
• /etc/host.conf
636
• /etc/hosts
• /etc/resolv.conf
These files are copied to /var/lib/dhcp/etc/ when starting the init script. Take
these copies into account for any changes that they require if they are dynamically
modified by scripts like /etc/ppp/ip-up. However, there should be no need to
worry about this if the configuration file only specifies IP addresses (instead of hostnames).
If your configuration includes additional files that should be copied into the chroot environment, set these under the variable DHCPD_CONF_INCLUDE_FILES in the file
/etc/sysconfig/dhcpd. To ensure that the DHCP logging facility keeps working
even after a restart of the syslog daemon, it is necessary to add the option "-a
/var/lib/dhcp/dev/log" under SYSLOGD_PARAMS in the file /etc/
sysconfig/syslog.
43.4
For More Information
More information about DHCP is available at the Web site of the Internet Software
Consortium (http://www.isc.org/products/DHCP/). Information is also
available in the dhcpd, dhcpd.conf, dhcpd.leases, and dhcp-options man
pages.
DHCP
637
Time Synchronization with xntp
44
The NTP (network time protocol) mechanism is a protocol for synchronizing the system
time over the network. First, a machine can obtain the time from a server that is a reliable
time source. Second, a machine can itself act as a time source for other computers in
the network. The goal is twofold—maintaining the absolute time and synchronizing
the system time of all machines within a network.
Maintaining an exact system time is important in many situations. The built-in hardware
(BIOS) clock does often not meet the requirements of applications like databases.
Manual correction of the system time would lead to severe problems because, for example, a backward leap can cause malfunction of critical applications. Within a network,
it is usually necessary to synchronize the system time of all machines, but manual time
adjustment is a bad approach. xntp provides an mechanism to solve these problems. It
continuously adjusts the system time with the help of reliable time servers in the network.
It further enables the management of local reference clocks, such as radio-controlled
clocks.
44.1
Configuring an NTP Client with
YaST
xntp is preset to use the local computer clock as a time reference. Using the (BIOS)
clock, however, only serves as a fallback for the case that no time source of greater
precision is available. SUSE Linux facilitates the configuration of an NTP client with
YaST. Use the quick or complex configuration for clients that do no run the SuSEfirewall
because they are part of a protected intranet. Both are described in the following.
Time Synchronization with xntp
639
44.1.1 Quick NTP Client Configuration
The easy NTP client configuration (Network Services → NTP Client) consists of two
dialogs. Set the start mode of xntpd and the server to query in the first dialog. To start
xntpd automatically when the system is booted, click During Boot. Then click Select
to access a second dialog in which to select a suitable time server for your network.
Figure 44.1
YaST: Configuring an NTP Client
In the detailed server selection dialog, determine whether to implement time synchronization using a time server from your local network (Local NTP Server) or an Internetbased time server that takes care of your time zone (Public NTP Server). For a local
time server, click Lookup to start an SLP query for available time servers in your network. Select the most suitable time server from the list of search results and exit the
dialog with OK. For a public time server, select your country (time zone) and a suitable
server from the list under Public NTP Server then exit the dialog with OK. In the main
dialog, test the availability of the selected server with Test and quit the dialog with
Finish.
640
44.1.2 Complex NTP Client Configuration
The complex configuration of an NTP client can be accessed under Complex Configuration from the main dialog of the NTP Client module, shown in Figure 44.1, “YaST:
Configuring an NTP Client” (page 640), after selecting the start-up mode as described
in the quick configuration.
Figure 44.2
YaST: Complex NTP Client Configuration
In Complex NTP Client Configuration, determine whether xntpd should be started in
a chroot jail. This increases the security in the event of an attack over xntpd, because
it prevents the attacker from compromising the entire system. Configure NTP Daemon
via DHCP sets up the NTP client to get a list of the NTP servers available in your network via DHCP.
The servers and other time sources for the client to query are listed in the lower part.
Modify this list as needed with Add, Edit, and Delete. Display Log provides the possibility to view the log files of your client.
Click Add to add a new source of time information. In the following dialog, select the
type of source with which the time synchronization should be made. The following
options are available:
Time Synchronization with xntp
641
Server
Another dialog enables you to select an NTP server (as described in Section 44.1.1,
“Quick NTP Client Configuration” (page 640)). Activate Use for Initial Synchronization to trigger the synchronization of the time information between the server and
the client when the system is booted. An input field allows you to specify additional
options for xntpd. Refer to /usr/share/doc/packages/xntp-doc (part
of the xntp-doc package) for detailed information.
Peer
A peer is a machine to which a symmetric relationship is established: it acts both
as a time server and as a client. To use a peer in the same network instead of a
server, enter the address of the system. The rest of the dialog is identical to the
Server dialog.
Radio Clock
To use a radio clock in your system for the time synchronization, enter the clock
type, unit number, device name, and other options in this dialog. Click Driver Calibration to fine-tune the driver. Detailed information about the operation of a local
radio clock is available in /usr/share/doc/packages/xntp-doc/html/
refclock.htm.
Outgoing Broadcast
Time information and queries can also be transmitted by broadcast in the network.
In this dialog, enter the address to which such broadcasts should be sent. Do not
activate broadcasting unless you have a reliable time source like a radio controlled
clock.
Incoming Broadcast
If you want your client to receive its information via broadcast, enter the address
from which the respective packets should be accepted in this fields.
44.2
Configuring xntp in the
Network
The easiest way to use a time server in the network is to set server parameters. For example, if a time server called ntp.example.com is reachable from the network, add
its name to the file /etc/ntp.conf by adding the line server
642
ntp.example.com. To add more time servers, insert additional lines with the keyword server. After initializing xntpd with the command rcxntpd start, it takes
about one hour until the time is stabilized and the drift file for correcting the local
computer clock is created. With the drift file, the systematic error of the hardware clock
can be computed as soon as the computer is powered on. The correction is used immediately, resulting in a higher stability of the system time.
There are two possible ways to use the NTP mechanism as a client: First, the client can
query the time from a known server in regular intervals. With many clients, this approach
can cause a high load on the server. Second, the client can wait for NTP broadcasts sent
out by broadcast time servers in the network. This approach has the disadvantage that
the quality of the server is unknown and a server sending out wrong information can
cause severe problems.
If the time is obtained via broadcast, you do not need the server name. In this case, enter
the line broadcastclient in the configuration file /etc/ntp.conf. To use one
or more known time servers exclusively, enter their names in the line starting with
servers.
44.3
Setting Up a Local Reference
Clock
The software package xntp contains drivers for connecting local reference clocks. A
list of supported clocks is available in the xntp-doc package in the file /usr/
share/doc/packages/xntp-doc/html/refclock.htm. Every driver is
associated with a number. In xntp, the actual configuration takes place by means of
pseudo IPs. The clocks are entered in the file /etc/ntp.conf as though they existed
in the network. For this purpose, they are assigned special IP addresses in the form
127.127.t.u. Here, t stands for the type of the clock and determines which driver
is used and u for unit, which determines the interface used.
Normally, the individual drivers have special parameters that describe configuration
details. The file /usr/share/doc/packages/xntp-doc/html/driverNN
.htm (where NN is the number of the driver) provides information about the particular
type of clock. For example, the “type 8” clock (radio clock over serial interface) requires
an additional mode that specifies the clock more precisely. The Conrad DCF77 receiver
module, for example, has mode 5. To use this clock as a preferred reference, specify
Time Synchronization with xntp
643
the keyword prefer. The complete server line for a Conrad DCF77 receiver
module would be:
server 127.127.8.0 mode 5 prefer
Other clocks follow the same pattern. Following the installation of the xntp-doc
package, the documentation for xntp is available in the directory /usr/share/doc/
packages/xntp-doc/html. The file /usr/share/doc/packages/
xntp-doc/html/refclock.htm provides links to the driver pages describing
the driver parameters.
644
LDAP—A Directory Service
45
The Lightweight Directory Access Protocol (LDAP) is a set of protocols designed to
access and maintain information directories. LDAP can be used for numerous purposes,
like user and group management, system configuration management, or address management. This chapter provides a basic understanding of how OpenLDAP works and
how to manage LDAP data with YaST. While there are several implementations of the
LDAP protocol, this chapter focuses entirely on the OpenLDAP implementation.
It is crucial within a networked environment to keep important information structured
and quickly available. This can be done with a directory service that, like the common
yellow pages, keeps information available in a well-structured, quickly searchable form.
In the ideal case, a central server keeps the data in a directory and distributes it to all
clients using a certain protocol. The data is structured in a way that allows a wide range
of applications to access it. That way, it is not necessary for every single calendar tool
and e-mail client to keep its own database—a central repository can be accessed instead.
This notably reduces the administration effort for the information. The use of an open
and standardized protocol like LDAP ensures that as many different client applications
as possible can access such information.
A directory in this context is a type of database optimized for quick and effective
reading and searching:
• To make numerous (concurrent) reading accesses possible, write access is limited
to a small number of updates by the administrator. Conventional databases are optimized for accepting the largest possible data volume in a short time.
LDAP—A Directory Service
645
• Because write accesses can only be executed in a restricted fashion, a directory
service is employed for administering mostly unchanging, static information. Data
in a conventional database typically changes very often (dynamic data). Phone
numbers in a company directory do not change nearly as often as, for example, the
figures administered in accounting.
• When static data is administered, updates of the existing data sets are very rare.
When working with dynamic data, especially when data sets like bank accounts or
accounting are concerned, the consistency of the data is of primary importance. If
an amount should be subtracted from one place to be added to another, both operations must happen concurrently, within a transaction, to ensure balance over the
data stock. Databases support such transactions. Directories do not. Short-term inconsistencies of the data are quite acceptable in directories.
The design of a directory service like LDAP is not laid out to support complex update
or query mechanisms. All applications accessing this service should gain access
quickly and easily.
Many directory services have previously existed and still exist both in Unix and outside
it. Novell NDS, Microsoft ADS, Banyan's Street Talk, and the OSI standard X.500 are
just a few examples. LDAP was originally planned as a lean flavor of DAP, the directory access protocol, which was developed for accessing X.500. The X.500 standard
regulates the hierarchical organization of directory entries.
LDAP is a trimmed down version of DAP. Without losing the X.500 entry hierarchy,
profit from LDAP's cross-platform capabilities and save resources. The use of TCP/IP
makes it substantially easier to establish interfaces between a docking application and
the LDAP service.
LDAP, meanwhile, has evolved and is increasingly employed as a stand-alone solution
without X.500 support. LDAP supports referrals with LDAPv3 (the protocol version
in package openldap2), making it possible to have distributed databases. The usage
of SASL (simple authentication and security layer) is also new.
LDAP is not limited to querying data from X.500 servers, as it was originally planned.
There is an open source server slapd, which can store object information in a local
database. There is also an extension called slurpd, which is responsible for replicating
multiple LDAP servers.
The openldap2 package consists of:
646
slapd
A stand-alone LDAPv3 server that administers object information in a BerkeleyDBbased database.
slurpd
This program enables the replication of modifications to data on the local LDAP
server to other LDAP servers installed on the network.
additional tools for system maintenance
slapcat, slapadd, slapindex
45.1
LDAP versus NIS
The Unix system administrator traditionally uses the NIS service for name resolution
and data distribution in a network. The configuration data contained in the files in /etc
and the directories group, hosts, mail, netgroup, networks, passwd,
printcap, protocols, rpc, and services are distributed by clients all over the
network. These files can be maintained without major effort because they are simple
text files. The handling of larger amounts of data, however, becomes increasingly difficult due to nonexistent structuring. NIS is only designed for Unix platforms. So, it
isn't suitable as a centralized data administration tool in heterogenous networks.
Unlike NIS, the LDAP service is not restricted to pure Unix networks. Windows servers
(from 2000) support LDAP as a directory service. Novell also offers an LDAP service.
Application tasks mentioned above are additionally supported in non-Unix systems.
The LDAP principle can be applied to any data structure that should be centrally administered. A few application examples are:
• Employment as a replacement for the NIS service
• Mail routing (postfix, sendmail)
• Address books for mail clients, like Mozilla, Evolution, and Outlook
• Administration of zone descriptions for a BIND9 name server
• User authentication with Samba in heterogeneous networks
LDAP—A Directory Service
647
This list can be extended because LDAP is extensible, unlike NIS. The clearly-defined
hierarchical structure of the data eases the administration of large amounts of data, because it can be searched better.
45.2
Structure of an LDAP Directory
Tree
An LDAP directory has a tree structure. All entries (called objects) of the directory
have a defined position within this hierarchy. This hierarchy is called the directory information tree (DIT). The complete path to the desired entry, which unambiguously
identifies it, is called distinguished name or DN. A single node along the path to this
entry is called relative distinguished name or RDN. Objects can generally be assigned
to one of two possible types:
container
These objects can themselves contain other objects. Such object classes are root
(the root element of the directory tree, which does not really exist), c (country), ou
(organizational unit), and dc (domain component). This model is comparable to
the directories (folders) in a file system.
leaf
These objects sit at the end of a branch and have no subordinate objects. Examples
are person, InetOrgPerson, or groupofNames.
The top of the directory hierarchy has a root element root. This can contain c (country),
dc (domain component), or o (organization) as subordinate elements. The relations
within an LDAP directory tree become more evident in the following example, shown
in Figure 45.1, “Structure of an LDAP Directory” (page 649).
648
Figure 45.1
Structure of an LDAP Directory
The complete diagram comprises a fictional directory information tree. The entries on
three levels are depicted. Each entry corresponds to one box in the picture. The complete,
valid distinguished name for the fictional SUSE employee Geeko Linux, in this
case, is cn=Geeko Linux,ou=doc,dc=suse,dc=de. It is composed by adding
the RDN cn=Geeko Linux to the DN of the preceding entry
ou=doc,dc=suse,dc=de.
The global determination of which types of objects should be stored in the DIT is done
following a scheme. The type of an object is determined by the object class. The object
class determines what attributes the concerned object must or can be assigned. A scheme,
therefore, must contain definitions of all object classes and attributes used in the desired
application scenario. There are a few common schemes (see RFC 2252 and 2256). It
is, however, possible to create custom schemes or to use multiple schemes complementing each other if this is required by the environment in which the LDAP server should
operate.
Table 45.1, “Commonly Used Object Classes and Attributes” (page 650) offers a small
overview of the object classes from core.schema and inetorgperson.schema
used in the example, including required attributes and valid attribute values.
LDAP—A Directory Service
649
Table 45.1
Commonly Used Object Classes and Attributes
Object Class
Meaning
Example En- Compulsory
try
Attributes
dcObject
domainComponent (name
components of the domain)
suse
dc
organizationalUnit
organizationalUnit (organizational unit)
doc
ou
inetOrgPerson
inetOrgPerson (person-related Geeko Linux
data for the intranet or Internet)
sn and cn
Example 45.1, “Excerpt from schema.core ” (page 650) shows an excerpt from a scheme
directive with explanations (line numbering for explanatory reasons).
Example 45.1
Excerpt from schema.core
#1 attributetype (2.5.4.11 NAME ( 'ou' 'organizationalUnitName')
#2
DESC 'RFC2256: organizational unit this object belongs to'
#3
SUP name )
...
#4 objectclass ( 2.5.6.5 NAME 'organizationalUnit'
#5
DESC 'RFC2256: an organizational unit'
#6
SUP top STRUCTURAL
#7
MUST ou
#8 MAY (userPassword $ searchGuide $ seeAlso $ businessCategory
$ x121Address $ registeredAddress $ destinationIndicator
$ preferredDeliveryMethod $ telexNumber
$ teletexTerminalIdentifier $ telephoneNumber
$ internationaliSDNNumber $ facsimileTelephoneNumber
$ street $ postOfficeBox $ postalCode $ postalAddress
$ physicalDeliveryOfficeName
$ st $ l $ description) )
...
The attribute type organizationalUnitName and the corresponding object class
organizationalUnit serve as an example here. Line 1 features the name of the
attribute, its unique OID (object identifier) (numerical), and the abbreviation of the attribute.
650
Line 2 gives brief description of the attribute with DESC. The corresponding RFC on
which the definition is based is also mentioned here. SUP in line 3 indicates a superordinate attribute type to which this attribute belongs.
The definition of the object class organizationalUnit begins in line 4, like in
the definition of the attribute, with an OID and the name of the object class. Line 5
features a brief description of the object class. Line 6, with its entry SUP top, indicates
that this object class is not subordinate to another object class. Line 7, starting with
MUST, lists all attribute types that must be used in conjunction with an object of the
type organizationalUnit. Line 8, starting with MAY, lists all attribute types that
are permitted in conjunction with this object class.
A very good introduction to the use of schemes can be found in the documentation of
OpenLDAP. When installed, find it in /usr/share/doc/packages/openldap2/
admin-guide/index.html.
45.3
Server Configuration with
slapd.conf
Your installed system contains a complete configuration file for your LDAP server at
/etc/openldap/slapd.conf. The single entries are briefly described here and
necessary adjustments are explained. Entries prefixed with a hash (#) are inactive. This
comment character must be removed to activate them.
45.3.1 Global Directives in slapd.conf
Example 45.2
slapd.conf: Include Directive for Schemes
include
include
include
include
include
/etc/openldap/schema/core.schema
/etc/openldap/schema/cosine.schema
/etc/openldap/schema/inetorgperson.schema
/etc/openldap/schema/rfc2307bis.schema
/etc/openldap/schema/yast.schema
This first directive in slapd.conf, shown in Example 45.2, “slapd.conf: Include
Directive for Schemes” (page 651), specifies the scheme by which the LDAP directory
is organized. The entry core.schema is compulsory. Additionally required schemes
LDAP—A Directory Service
651
are appended to this directive. Information can be found in the included OpenLDAP
documentation.
Example 45.3
slapd.conf: pidfile and argsfile
pidfile /var/run/slapd/slapd.pid
argsfile /var/run/slapd/slapd.args
These two files contain the PID (process ID) and some of the arguments with which
the slapd process is started. There is no need for modifications here.
Example 45.4
slapd.conf: Access Control
# Sample Access Control
#
Allow read access of root DSE
# Allow self write access
#
Allow authenticated users read access
#
Allow anonymous users to authenticate
# access to dn="" by * read
access to * by self write
by users read
by anonymous auth
#
# if no access controls are present, the default is:
#
Allow read by all
#
# rootdn can always write!
Example 45.4, “slapd.conf: Access Control” (page 652) is the excerpt from slapd
.conf that regulates the access permissions for the LDAP directory on the server. The
settings made here in the global section of slapd.conf are valid as long as no custom
access rules are declared in the database-specific section. These would overwrite the
global declarations. As presented here, all users have read access to the directory, but
only the administrator (rootdn) can write to this directory. Access control regulation
in LDAP is a highly complex process. The following tips can help:
• Every access rule has the following structure:
access to <what> by <who> <access>
• what is a placeholder for the object or attribute to which access is granted. Individual directory branches can be protected explicitly with separate rules. It is also
possible to process regions of the directory tree with one rule by using regular expressions. slapd evaluates all rules in the order in which they are listed in the
configuration file. More general rules should be listed after more specific ones—the
first rule slapd regards as valid is evaluated and all following entries are ignored.
652
• who determines who should be granted access to the areas determined with what.
Regular expressions may be used. slapd again aborts the evaluation of who after
the first match, so more specific rules should be listed before the more general ones.
The entries shown in Table 45.2, “User Groups and Their Access Grants” (page 653)
are possible.
Table 45.2
User Groups and Their Access Grants
Tag
Scope
*
All users without exception
anonymous
Not authenticated (“anonymous”) users
users
Authenticated users
self
Users connected with the target object
dn.regex=<regex>
All users matching the regular expression
• access specifies the type of access. Use the options listed in Table 45.3, “Types
of Access” (page 653).
Table 45.3
Types of Access
Tag
Scope of Access
none
No access
auth
For contacting the server
compare
To objects for comparison access
search
For the employment of search filters
read
Read access
write
Write access
LDAP—A Directory Service
653
slapd compares the access right requested by the client with those granted in
slapd.conf. The client is granted access if the rules allow a higher or equal
right than the requested one. If the client requests higher rights than those declared
in the rules, it is denied access.
Example 45.5, “slapd.conf: Example for Access Control” (page 654) shows an example
of a simple access control that can be arbitrarily developed using regular expressions.
Example 45.5
slapd.conf: Example for Access Control
access to dn.regex="ou=([^,]+),dc=suse,dc=de"
by dn.regex="cn=administrator,ou=$1,dc=suse,dc=de" write
by user read
by * none
This rule declares that only its respective administrator has write access to an individual
ou entry. All other authenticated users have read access and the rest of the world has
no access.
TIP: Establishing Access Rules
If there is no access to rule or no matching by directive, access is denied.
Only explicitly declared access rights are granted. If no rules are declared at
all, the default principle is write access for the administrator and read access
for the rest of the world.
Find detailed information and an example configuration for LDAP access rights in the
online documentation of the installed openldap2 package.
Apart from the possibility to administer access permissions with the central server
configuration file (slapd.conf), there is access control information (ACI). ACI allows
storage of the access information for individual objects within the LDAP tree. This type
of access control is not yet common and is still considered experimental by the developers. Refer to http://www.openldap.org/faq/data/cache/758.html
for information.
654
45.3.2 Database-Specific Directives in
slapd.conf
Example 45.6
slapd.conf: Database-Specific Directives
database bdb
checkpoint
1024
5
cachesize
10000
suffix "dc=suse,dc=de"
rootdn "cn=admin,dc=suse,dc=de"
# Cleartext passwords, especially for the rootdn, should
# be avoided. See slappasswd(8) and slapd.conf(5) for details.
# Use of strong authentication encouraged.
rootpw secret
# The database directory MUST exist prior to running slapd AND
# should only be accessible by the slapd/tools. Mode 700 recommended.
directory /var/lib/ldap
# Indices to maintain
index
objectClass
eq
The type of database, a Berkeley database in this case, is determined in the first line of
this section (see Example 45.6, “slapd.conf: Database-Specific Directives” (page 655)).
checkpoint determines the amount of data (in kb) that is kept in the transaction log
before it is written to the actual database and the time (in minutes) between two write
actions. cachesize sets the number of objects kept in the database's cache. suffix
determines for which portion of the LDAP tree this server should be responsible. The
following rootdn determines who owns administrator rights to this server. The user
declared here does not need to have an LDAP entry or exist as regular user. The administrator password is set with rootpw. Instead of using secret here, it is possible to
enter the hash of the administrator password created by slappasswd. The
directory directive indicates the directory (in the file system) where the database
directories are stored on the server. The last directive, index objectClass eq,
results in the maintenance of an index of all object classes. Attributes for which users
search most often can be added here according to experience. Custom Access rules
defined here for the database are used instead of the global Access rules.
45.3.3 Starting and Stopping the Servers
Once the LDAP server is fully configured and all desired entries have been made according to the pattern described in Section 45.4, “Data Handling in the LDAP Directory”
(page 656), start the LDAP server as root by entering rcldap start. To stop the
LDAP—A Directory Service
655
server manually, enter the command rcldap stop. Request the status of the running
LDAP server with rcldap status.
The YaST runlevel editor, described in Section 28.2.3, “Configuring System Services
(Runlevel) with YaST” (page 422), can be used to have the server started and stopped
automatically on boot and halt of the system. It is also possible to create the corresponding links to the start and stop scripts with the insserv command from a command
prompt as described in Section 28.2.2, “Init Scripts” (page 418).
45.4
Data Handling in the LDAP
Directory
OpenLDAP offers a series of tools for the administration of data in the LDAP directory.
The four most important tools for adding to, deleting from, searching through, and
modifying the data stock are briefly explained below.
45.4.1 Inserting Data into an LDAP
Directory
Once the configuration of your LDAP server in /etc/openldap/lsapd.conf is
correct and ready to go (it features appropriate entries for suffix, directory,
rootdn, rootpw, and index), proceed to entering records. OpenLDAP offers the
ldapadd command for this task. If possible, add the objects to the database in bundles
for practical reasons. LDAP is able to process the LDIF format (LDAP data interchange
format) for this. An LDIF file is a simple text file that can contain an arbitrary number
of pairs of attribute and value. Refer to the schema files declared in slapd.conf for
the available object classes and attributes. The LDIF file for creating a rough framework
for the example in Figure 45.1, “Structure of an LDAP Directory” (page 649) would
look like that in Example 45.7, “Example for an LDIF File” (page 657).
656
Example 45.7
Example for an LDIF File
# The SUSE Organization
dn: dc=suse,dc=de
objectClass: dcObject
objectClass: organization
o: SUSE AG dc: suse
# The organizational unit development (devel)
dn: ou=devel,dc=suse,dc=de
objectClass: organizationalUnit
ou: devel
# The organizational unit documentation (doc)
dn: ou=doc,dc=suse,dc=de
objectClass: organizationalUnit
ou: doc
# The organizational unit internal IT (it)
dn: ou=it,dc=suse,dc=de
objectClass: organizationalUnit
ou: it
IMPORTANT: Encoding of LDIF Files
LDAP works with UTF-8 (Unicode). Umlauts must be encoded correctly. Use
an editor that supports UTF-8, such as Kate or recent versions of Emacs. Otherwise, avoid umlauts and other special characters or use recode to recode the
input to UTF-8.
Save the file with the .ldif suffix then pass it to the server with the following command:
ldapadd -x -D <dn of the administrator> -W -f <file>.ldif
-x switches off the authentication with SASL in this case. -D declares the user that
calls the operation. The valid DN of the administrator is entered here just like it has
been configured in slapd.conf. In the current example, this is
cn=admin,dc=suse,dc=de. -W circumvents entering the password on the command
line (in clear text) and activates a separate password prompt. This password was previously determined in slapd.conf with rootpw. -f passes the filename. See the
details of running ldapadd in Example 45.8, “ldapadd with example.ldif” (page 658).
LDAP—A Directory Service
657
Example 45.8
ldapadd with example.ldif
ldapadd -x -D cn=admin,dc=suse,dc=de -W -f example.ldif
Enter LDAP
adding new
adding new
adding new
adding new
password:
entry "dc=suse,dc=de"
entry "ou=devel,dc=suse,dc=de"
entry "ou=doc,dc=suse,dc=de"
entry "ou=it,dc=suse,dc=de"
The user data of individuals can be prepared in separate LDIF files. Example 45.9,
“LDIF Data for Tux” (page 658) adds Tux to the new LDAP directory.
Example 45.9
LDIF Data for Tux
# coworker Tux
dn: cn=Tux Linux,ou=devel,dc=suse,dc=de
objectClass: inetOrgPerson
cn: Tux Linux
givenName: Tux
sn: Linux
mail: [email protected]
uid: tux
telephoneNumber: +49 1234 567-8
An LDIF file can contain an arbitrary number of objects. It is possible to pass entire
directory branches to the server at once or only parts of it as shown in the example of
individual objects. If it is necessary to modify some data relatively often, a fine subdivision of single objects is recommended.
45.4.2 Modifying Data in the LDAP
Directory
The tool ldapmodify is provided for modifying the data stock. The easiest way to
do this is to modify the corresponding LDIF file then pass this modified file to the
LDAP server. To change the telephone number of colleague Tux from +49 1234
567-8 to +49 1234 567-10, edit the LDIF file like in Example 45.10, “Modified
LDIF File tux.ldif” (page 659).
658
Example 45.10
Modified LDIF File tux.ldif
# coworker Tux
dn: cn=Tux Linux,ou=devel,dc=suse,dc=de
changetype: modify
replace: telephoneNumber
telephoneNumber: +49 1234 567-10
Import the modified file into the LDAP directory with the following command:
ldapmodify -x -D cn=admin,dc=suse,dc=de -W -f tux.ldif
Alternatively, pass the attributes to change directly to ldapmodify. The procedure
for this is described below:
1.
Start ldapmodify and enter your password:
ldapmodify -x -D cn=admin,dc=suse,dc=de -W
Enter LDAP password:
2.
Enter the changes while carefully complying with the syntax in the order presented below:
dn: cn=Tux Linux,ou=devel,dc=suse,dc=de
changetype: modify
replace: telephoneNumber
telephoneNumber: +49 1234 567-10
Find detailed information about ldapmodify and its syntax in the ldapmodify(1)
man page.
45.4.3 Searching or Reading Data from an
LDAP Directory
OpenLDAP provides, with ldapsearch, a command line tool for searching data
within an LDAP directory and reading data from it. A simple query would have the
following syntax:
ldapsearch -x -b dc=suse,dc=de "(objectClass=*)"
The option -b determines the search base—the section of the tree within which the
search should be performed. In the current case, this is dc=suse,dc=de. To perform
a more finely-grained search in specific subsections of the LDAP directory (for example,
LDAP—A Directory Service
659
only within the devel department), pass this section to ldapsearch with -b. -x
requests activation of simple authentication. (objectClass=*) declares that all
objects contained in the directory should be read. This command option can be used
after the creation of a new directory tree to verify that all entries have been recorded
correctly and the server responds as desired. More information about the use of
ldapsearch can be found in the corresponding man page (ldapsearch(1)).
45.4.4 Deleting Data from an LDAP
Directory
Delete unwanted entries with ldapdelete. The syntax is similar to that of the commands described above. To delete, for example, the complete entry for Tux Linux,
issue the following command:
ldapdelete -x -D cn=admin,dc=suse,dc=de -W cn=Tux \
Linux,ou=devel,dc=suse,dc=de
45.5
The YaST LDAP Client
YaST includes a module to set up LDAP-based user management. If you did not enable
this feature during the installation, start the module by selecting Network Services →
LDAP Client. YaST automatically enables any PAM and NSS related changes as required
by LDAP (described below) and installs the necessary files.
45.5.1 Standard Procedure
Background knowledge of the processes acting in the background of a client machine
helps you understand how the YaST LDAP client module works. If LDAP is activated
for network authentication or the YaST module is called, the packages pam_ldap and
nss_ldap are installed and the two corresponding configuration files are adapted.
pam_ldap is the PAM module responsible for negotiation between login processes
and the LDAP directory as the source of authentication data. The dedicated module
pam_ldap.so is installed and the PAM configuration is adapted (see Example 45.11,
“pam_unix2.conf Adapted to LDAP” (page 661)).
660
Example 45.11
auth:
account:
password:
session:
pam_unix2.conf Adapted to LDAP
use_ldap
use_ldap
use_ldap
none
When manually configuring additional services to use LDAP, include the PAM LDAP
module in the PAM configuration file corresponding to the service in /etc/pam.d.
Configuration files already adapted to individual services can be found in /usr/
share/doc/packages/pam_ldap/pam.d/. Copy appropriate files to /etc/
pam.d.
glibc name resolution through the nsswitch mechanism is adapted to the employment of LDAP with nss_ldap. A new, adapted file nsswitch.conf is created in
/etc/ with the installation of this package. More about the workings of nsswitch
.conf can be found in Section 38.5.1, “Configuration Files” (page 577). The following
lines must be present in nsswitch.conf for user administration and authentication
with LDAP. See Example 45.12, “Adaptations in nsswitch.conf” (page 661).
Example 45.12
Adaptations in nsswitch.conf
passwd: compat
group: compat
passwd_compat: ldap
group_compat: ldap
These lines order the resolver library of glibc first to evaluate the corresponding files
in /etc and additionally access the LDAP server as sources for authentication and
user data. Test this mechanism, for example, by reading the content of the user database
with the command getent passwd. The returned set should contain a survey of the
local users of your system as well as all users stored on the LDAP server.
To prevent regular users managed through LDAP from logging in to the server with
ssh or login, the files /etc/passwd and /etc/group each need to include an
additional line. This is the line +::::::/sbin/nologin in /etc/passwd and
+::: in /etc/group.
LDAP—A Directory Service
661
45.5.2 Configuration of the LDAP Client
After the initial adjustments of nss_ldap, pam_ldap, /etc/passwd, and /etc/
group have been taken care of by YaST, you can simply connect your client to the
server and let YaST do user management via LDAP. This basic setup is described in
Section “Basic Configuration” (page 662).
Use the YaST LDAP client to further configure the YaST group and user configuration
modules. This includes manipulating the default settings for new users and groups and
the number and nature of the attributes assigned to a user or a group. LDAP user management allows you to assign far more and different attributes to users and groups than
traditional user or group management solutions. This is described in Section “Configuring the YaST Group and User Administration Modules” (page 665).
Basic Configuration
The basic LDAP client configuration dialog (Figure 45.2, “YaST: Configuration of the
LDAP Client” (page 663)) opens during installation if you choose LDAP user management or when you select Network Services → LDAP Client in the YaST Control Center
in the installed system.
662
Figure 45.2
YaST: Configuration of the LDAP Client
To authenticate users of your machine against an OpenLDAP server and enable user
management via OpenLDAP, proceed as follows:
1 Click Use LDAP to enable the use of LDAP. Select Use LDAP but Disable Logins
instead if you want to use LDAP for authentication, but do not want other users
to log in to this client.
2 Enter the IP address of the LDAP server to use.
3 Enter the LDAP base DN to select the search base on the LDAP server.
4 If TLS or SSL protected communication with the server is required, select LDAP
TLS/SSL.
5 If the LDAP server still uses LDAPv2, explicitly enable the use of this protocol
version by selecting LDAP Version 2.
6 Select Start Automounter to mount remote directories on your client, such as a
remotely managed /home.
7 Click Finish to apply your settings.
LDAP—A Directory Service
663
Figure 45.3
YaST: Advanced Configuration
To modify data on the server as administrator, click Advanced Configuration. The
following dialog is split in two tabs. See Figure 45.3, “YaST: Advanced Configuration”
(page 664):
1 In the Client Settings tab, adjust the following settings to your needs:
a If the search base for users, passwords, and groups differs from the global
search base specified the LDAP base DN, enter these different naming
contexts in User Map, Password Map, and Group Map.
b Specify the password change protocol. The standard method to use whenever
a password is changed is crypt, meaning that password hashes generated
by crypt are used. For details on this and other options, refer to the
pam_ldap man page.
c Specify the LDAP group to use with Group Member Attribute. The default
value for this is member.
2 In Administration Settings, adjust the following settings:
664
a Set the base for storing your user management data via Configuration Base
DN.
b Enter the appropriate value for Administrator DN. This DN must be identical
with the rootdn value specified in /etc/openldap/slapd.conf to
enable this particular user to manipulate data stored on the LDAP server.
c Check Create Default Configuration Objects to create the basic configuration
objects on the server to enable user management via LDAP.
d If your client machine should act as a file server for home directories across
your network, check Home Directories on This Machine.
e Click Accept to leave the Advanced Configuration then Finish to apply your
settings.
Use Configure User Management Settings to edit entries on the LDAP server. Access
to the configuration modules on the server is then granted according to the ACLs and
ACIs stored on the server. Follow the procedures outlined in Section “Configuring the
YaST Group and User Administration Modules” (page 665).
Configuring the YaST Group and User Administration
Modules
Use the YaST LDAP client to adapt the YaST modules for user and group administration
and to extend them as needed. Define templates with default values for the individual
attributes to simplify the data registration. The presets created here are stored as LDAP
objects in the LDAP directory. The registration of user data is still done with the regular
YaST modules for user and group management. The registered data is stored as LDAP
objects on the server.
LDAP—A Directory Service
665
Figure 45.4
YaST: Module Configuration
The dialog for module configuration (Figure 45.4, “YaST: Module Configuration”
(page 666)) allows the creation of new modules, selection and modification of existing
configuration modules, and design and modification of templates for such modules.
To create a new configuration module, proceed as follows:
1 Click New and select the type of module to create. For a user configuration
module, select suseuserconfiguration and for a group configuration
choose susegroupconfiguration.
2 Choose a name for the new template.
The content view then features a table listing all attributes allowed in this module
with their assigned values. Apart from all set attributes, the list also contains all
other attributes allowed by the current schema but currently not used.
3 Accept the preset values or adjust the defaults to use in group and user configuration by selecting the respective attribute, pressing Edit, and entering the new
value. Rename a module by simply changing the cn attribute of the module.
Clicking Delete deletes the currently selected module.
666
4 After you click OK, the new module is added to the selection menu.
The YaST modules for group and user administration embed templates with sensible
standard values. To edit a template associated with a configuration module, proceed
as follows:
1 In the Module Configuration dialog, click Configure Template.
2 Determine the values of the general attributes assigned to this template according
to your needs or leave some of them empty. Empty attributes are deleted on the
LDAP server.
3 Modify, delete, or add new default values for new objects (user or group configuration objects in the LDAP tree).
Figure 45.5
YaST: Configuration of an Object Template
Connect the template to its module by setting the susedefaulttemplate attribute
value of the module to the DN of the adapted template.
LDAP—A Directory Service
667
TIP
The default values for an attribute can be created from other attributes by
using a variable instead of an absolute value. For example, when creating a
new user, cn=%sn %givenName is created automatically from the attribute
values for sn and givenName.
Once all modules and templates are configured correctly and ready to run, new groups
and users can be registered in the usual way with YaST.
45.6
Configuring LDAP Users and
Groups in YaST
The actual registration of user and group data differs only slightly from the procedure
when not using LDAP. The following brief instructions relate to the administration of
users. The procedure for administering groups is analogous.
1 Access the YaST user administration with Security & Users → User Administration.
2 Use Set Filter to limit the view of users to the LDAP users and enter the password
for Root DN.
3 Click Add and enter the configuration of a new user. A dialog with four tabs
opens:
a Specify username, login, and password in the User Data tab.
b Check the Details tab for the group membership, login shell, and home directory of the new user. If necessary, change the default to values that better
suit your needs. The default values as well as those of the password settings
can be defined with the procedure described in Section “Configuring the
YaST Group and User Administration Modules” (page 665).
c Modify or accept the default Password Settings.
668
d Enter the Plug-Ins tab, select the LDAP plug-in, and click Launch to configure additional LDAP attributes assigned to the new user (see Figure 45.6,
“YaST: Additional LDAP Settings” (page 669)).
4 Click Accept to apply your settings and leave the user configuration.
Figure 45.6
YaST: Additional LDAP Settings
The initial input form of user administration offers LDAP Options. This gives the possibility to apply LDAP search filters to the set of available users or go to the module
for the configuration of LDAP users and groups by selecting LDAP User and Group
Configuration.
45.7
For More Information
More complex subjects, like SASL configuration or establishment of a replicating
LDAP server that distributes the workload among multiple slaves, were intentionally
not included in this chapter. Detailed information about both subjects can be found in
the OpenLDAP 2.2 Administrator's Guide (references follow).
LDAP—A Directory Service
669
The Web site of the OpenLDAP project offers exhaustive documentation for beginning
and advanced LDAP users:
OpenLDAP Faq-O-Matic
A very rich question and answer collection concerning installation, configuration,
and use of OpenLDAP. Find it at http://www.openldap.org/faq/data/
cache/1.html.
Quick Start Guide
Brief step-by-step instructions for installing your first LDAP server. Find it at
http://www.openldap.org/doc/admin22/quickstart.html or on
an installed system in /usr/share/doc/packages/openldap2/
admin-guide/quickstart.html.
OpenLDAP 2.2 Administrator's Guide
A detailed introduction to all important aspects of LDAP configuration, including
access controls and encryption. See http://www.openldap.org/doc/
admin22/ or, on an installed system, /usr/share/doc/packages/
openldap2/admin-guide/index.html.
Understanding LDAP
A detailed general introduction to the basic principles of LDAP: http://www
.redbooks.ibm.com/redbooks/pdfs/sg244986.pdf.
Printed literature about LDAP:
• LDAP System Administration by Gerald Carter (ISBN 1-56592-491-6)
• Understanding and Deploying LDAP Directory Services by Howes, Smith, and
Good (ISBN 0-672-32316-8)
The ultimate reference material for the subject of LDAP is the corresponding RFCs
(request for comments), 2251 to 2256.
670
46
The Apache Web Server
With a share of more than 60%, Apache is the world's most widely-used Web server
according to http://www.netcraft.com. For Web applications, Apache is often
used on Linux, with the database MySQL, and the programming languages PHP and
Perl. This combination is commonly referred to as LAMP.
This chapter introduces the Web and application server software Apache in version 2.x.
Installation and configuration of Apache are explained here, along with the usage of
some of the available modules.
46.1
Preface and Terminology
This section provides definitions of frequently used terms, both Web-related and particular to Apache.
IMPORTANT: Terminology
In this document, the term Apache refers to Apache in version 2.x. For documentation on Apache 1.x, see http://httpd.apache.org/docs/.
46.1.1 Web Server
A Web server delivers Web pages requested by a client. The client can be a Web
browser, such as Konqueror, or any other device that can connect to the World Wide
The Apache Web Server
671
Web. These pages can be stored as a whole on disk (static pages) or generated in response
to a query (dynamic pages) of an external entity, such as a database or a Web service.
46.1.2 HTTP
Communication between the client and the Web server takes place using the hypertext
transfer protocol (HTTP). The current version, HTTP 1.1, is documented in RFC 2068
and in the update RFC 2616. These RFCs are available at http://www.w3.org.
46.1.3 URLs
URL stands for universal resource locator. Clients use URLs, such as http://www
.example.com/index.html, to request pages from the server. A URL consists
of:
Protocol
Frequently-used protocols:
http://
The HTTP protocol
https://
Secure, encrypted version of HTTP
ftp://
File transfer protocol for downloading and uploading files
Domain
In this example, the domain is www.example.com. The domain is the name that
corresponds to an IP address. Thus, www.example.com maps uniquely to an IP
address like 123.456.789.1. In turn, the number uniquely identifies the computer
running a Web server. The mapping of a domain name to an IP address is commonly
referred to as name resolution. The domain can be subdivided into several parts,
here: www, example, and com. The last part of the domain name is the top level
domain (TLD). In this example, com is the TLD. TLD represents the top level of
the name resolution process. TLDs can be generic (gTLDs, such as com, org, and
672
net) or country-specific (ccTLDs, such as de for Germany). All parts of a domain
together are referred to as the fully qualified domain name (FQDN).
Resource
In this example, the resource is index.html. This part specifies the full path to
the resource. The resource can be a file, as in this example. However, it can also be
a CGI script, a JavaServer page, or some other resource.
The responsible Internet mechanism, such as the domain name system (DNS) forwards
the query to the domain www.example.com to one or several computers holding the
resource. Apache then delivers the actual resource, in this example, the page index
.html, to the client. In this case, the file is located in the top level directory. However,
resources can also be located in subdirectories, as in http://www.example.com/
linux/novell/suse.
46.1.4 Directive
For configuring Apache, the term directive is often used as a synoynm for “configuration
option.” Directive is the technical term pertaining to the Apache Web server software.
46.2
Installation
Apache on SUSE Linux runs "out of the box" with a standard, predefined configuration.
By following the instructions in this chapter, can have the Apache Web server up and
running in little time. You must be root to install and configure Apache.
46.2.1 Installing Apache with YaST
The SUSE Linux apache2 package differs slightly in its file system and application
layout from the standard software package available on the Apache Web site (http://
httpd.apache.org). The following section describes the installation of the SUSE
Linux apache2 package in detail and denotes the variations where applicable.
To install a simple Web server, proceed as follows:
The Apache Web Server
673
Procedure 46.1
Quick Installation
1 Start YaST in GUI or command line mode.
2 Select Network Services → HTTP Server.
3 Click Continue to confirm the installation of packages apache2 and
apache2-prefork.
4 When the installation has finished, the Apache Configuration Wizard appears
and you can start configuring the Web server.
The disadvantage in preceeding as instructed above is that there is an absence of PHP
and database support. To install a Web server with PHP and database support, proceed
as follows:
Procedure 46.2
Installation of Simple Web Server
1 Start YaST in GUI or command line mode.
2 Select Software → Software Management.
3 Select Selections in Filter then check Simple Web Server with Apache2.
4 Press OK.
5 Confirm the installation of the dependent packages to finish the SUSE Linux
Apache2 installation process.
For advanced users, SUSE Linux offers custom package selection. To perform a custom
installation of a Web server, proceed as follows:
Procedure 46.3
Installation of the Default Apache RPM with YaST
1 Start YaST in GUI or command line mode. Select Software → Software Management.
2 Select Search in Filter then enter apache2 in the Search field.
3 Select apache2 for installation.
674
4 Use step 2 and 3 for module selection. See Section 46.5, “Apache Modules”
(page 700).
5 After selection press Accept.
6 You are then prompted to choose one of the dependencies for the necessary
apache2-MPM package: apache2-prefork or apache2-worker. Refer
to the Section 46.2.2, “Multiprocessing Modules” (page 675) for an explanation
of the differences between the two. If you are not sure, select the
apache2-prefork package, which is the default for Unix-based operating
systems then press OK.
7 Confirm the installation of the dependent packages to finish the SUSE Linux
Apache2 installation process.
NOTE: Starting a Web Server
Installing Apache does not start the Web server automatically. Refer to Section 46.3.3, “Activating, Starting, and Stopping Apache” (page 694) for information about controlling Apache start-up and shutdown.
46.2.2 Multiprocessing Modules
As mentioned in Installation of the Default Apache RPM with YaST (page 674), SUSE
Linux provides two different multiprocessing modules (MPMs) for use with Apache.
MPMs are responsible for accepting and handling requests to the Web server, representing the core of the Web server software.
Prefork MPM
The prefork MPM implements a nonthreaded, preforking Web server. It makes the Web
server behave similarly to Apache version 1.x in that it isolates each request and handles
it by forking a separate child process. Thus problematic requests cannot affect others,
avoiding a lockup of the Web server.
While providing stability with this process-based approach, the prefork MPM consumes
more system resources than its counterpart, the worker MPM. The prefork MPM is
considered the default MPM for Unix-based operating systems.
The Apache Web Server
675
IMPORTANT: MPMs in This Document
This document assumes Apache is used with the prefork MPM.
Worker MPM
The worker MPM provides a multithreaded web server. A thread is a “lighter” form of
a process. The advantage of a thread over a process is its lower resource consumption.
Instead of only forking child processes, the worker MPM serves requests by using
threads with server processes. The preforked child processes are multithreaded.
This approach makes Apache perform better by consuming fewer system resources
than the prefork MPM. One major disadvantage is the stability of the worker MPM: if
a thread becomes corrupt, all threads of a process can be affected. In the worst case,
this may result in a server crash. Especially when using CGI (described in Section
“Common Gateway Interface: mod_cgi ” (page 702)) with Apache under heavy load,
internal server errors might occur due to threads unable to communicate with system
resources.
Another argument against using the worker MPM with Apache is that not all available
Apache modules (see Section 46.5, “Apache Modules” (page 700)) are thread-safe and
thus cannot be used in conjunction with the worker MPM.
WARNING: PHP as an Apache Module (mod_php)
Not all available PHP modules are thread-safe. Using the worker MPM with
mod_php is strongly discouraged.
46.2.3 Default File System and Application
Layout
SUSE Linux places files of the Apache package into default locations. The locations
of the most important files are listed here.
676
Binaries
Most of the executable files in SUSE Linux Apache have a 2 appended to them. This
simplifies differentiation of binary files for a parallel installation of Apache 1.x and
Apache 2.x.
/usr/sbin/httpd2
Symbolic link pointing to the chosen multiprocessing module as described in Section 46.2.2, “Multiprocessing Modules” (page 675). The default is
httpd2-prefork. The symlink is maintained by the start script according to the
system configuration setting of the MPM.
/usr/sbin/httpd2-prefork
The actual Apache2 executable.
/usr/sbin/apache2ctl
Control script to start and stop the Web server, provided by the Apache HTTPD
project. See Section 46.3.3, “Activating, Starting, and Stopping Apache” (page 694)
for more information or run /usr/sbin/apache2ctl help.
/etc/init.d/apache2
Start and stop script providing full integration in the SUSE Linux installation and
starting Apache at boot time. It checks for a valid configuration before starting and
stopping the server and overrides the location of the configuration. It allows easy
inclusion of further configuration files, loading of modules, or even start of a
seperate instance of the server without modification of the script.
/usr/sbin/rcapache2
A convenient symlink for /etc/init.d/apache2, because /etc/init.d/
is not in the path by default. Simply use rcapache2 start to start Apache.
/usr/sbin/htpasswd2
Utility to generate encrypted passwords for .htaccess-based authentication.
Refer to the htpasswd2(1) man page for details on how to use the tool.
Configuration files
Most of the configuration files reside under /etc/apache2. For information about
how to change configuration settings, refer to Section 46.3, “Configuration” (page 680).
The Apache Web Server
677
/etc/apache2/httpd.conf
Top-level configuration file. If possible, avoid changes to this file. It mainly includes
other configuration files and declares global settings.
/etc/apache2/*.conf
Some external Apache modules put their configuration files in the directory /etc/
apache2/, usually prefixed with the module name itself (mod_*.conf).
/etc/apache2/conf.d/*
Directory holding various other configuration files that come with certain packages.
For an example, see Section “Serving PHP: mod_php4, mod_php5 ” (page 708).
/etc/apache2/vhosts.d/*
Directory holding the optional configuration files for virtual hosts. See Section 46.4,
“Virtual Hosts” (page 696) for details.
/etc/sysconfig/apache2
SUSE Linux configuration file relating to Apache2. It holds all relevant configuration
parameters for controlling the Apache Web server. /etc/sysconfig/apache2
is used by YaST for configuring Apache as described in Section 46.3.1, “Configuring
Apache with YaST” (page 680). It can also be edited manually as described in Section 46.3.2, “Configuring Apache Manually” (page 688).
Log Files
By default, Apache provides various information about its runtime status in the following
files:
/var/log/apache2/error_log
Apache logs start-up and shutdown notices and all runtime errors into this file.
/var/log/apache2/access_log
All requests to the Web server are logged into this file. The default format of the
entries is combined format, showing information about the host and user agent
sending the request and the referring URI.
678
Document Root
The physical directory /srv/www/htdocs is the default location from which Apache
serves Web pages. It acts as “root directory” for a client request. To publish Web pages
with Apache, store the files hierarchically in or under that directory.
A URL like http://www.example.com/index.html refers to /srv/www/htdocs/
index.html in the default Apache configuration in SUSE Linux for a domain named
example.com.
46.2.4 Building Modules Manually
Apache is built with a modular approach, meaning that modules provide the capabilities
of the Web server software itself. Consequently, Apache can be extended by advanced
users by writing custom modules. Refer to the man pages mentioned in the following
for more detailed information.
apache2-devel
To be able to develop modules for Apache or compile third-party modules, the package
apache2-devel is required along with the corresponding development tools.
apache2-devel also contains the apxs2 tools, which are necessary for compiling
additional modules for Apache.
apxs2
The apxs2 binaries are located under /usr/sbin:
• /usr/sbin/apxs2—suitable for building an extension module that works with
any MPM. The installation location is /usr/lib/apache2.
• /usr/sbin/apxs2-prefork—suitable for prefork MPM modules. The installation location is /usr/lib/apache2-prefork.
• /usr/sbin/apxs2-worker—suitable for worker MPM modules.
apxs2 installs modules so they can be used for all MPMs. The other two programs
install modules so they can only be used for the respective MPMs. apxs2 installs
The Apache Web Server
679
modules in /usr/lib/apache2 and apxs2-prefork installs modules in /usr/
lib/apache2-prefork.
apxs2 enables the compilation and installation of modules from source code (including
the required changes to the configuration files), which creates dynamic shared objects
(DSOs) that can be loaded into Apache at runtime. Install a module from source code
with the commands cd /path/to/module/source; apxs2 -c -i
mod_foo.c. Other options of apxs2 are described in the apxs2(1) man page. The
modules should then be activated in /etc/sysconfig/apache2 with the entry
APACHE_MODULES as described in Section 46.3.2, “Configuring Apache Manually”
(page 688).
46.3
Configuration
Apache in SUSE Linux can be configured in two different ways: with YaST or manually. Manual configuration offers a higher level of detail, but lacks the convenience of
the YaST GUI.
IMPORTANT: Configuration Changes
Changes to some configuration values for Apache only take effect after Apache
is restarted. This happens automatically when finishing the configuration using
YaST with Enabled checked for the HTTP Service. Manual restart is described
in Section 46.3.3, “Activating, Starting, and Stopping Apache” (page 694). Most
configuration changes only require a reload with rcapache2 reload.
46.3.1 Configuring Apache with YaST
With YaST, you can turn a host in your network into a Web server. To configure such
a server, start YaST and select Network Services → HTTP Server. When starting the
module for the first time, the HTTP Server Wizard starts, prompting you to make just
a few basic decisions concerning administration of the server.
680
HTTP Server Wizard
The HTTP Server Wizard consists of five steps or dialogs. In the last step of the dialog,
you are given the opportunity to enter the expert configuration mode to make even more
specific settings.
Network Device Selection
Here, specify the network interfaces and ports Apache uses to listen for incoming
requests. You can select any combination of existing network interfaces and their
respective IP addresses. Ports from all three ranges (well-known ports, registered
ports, and dynamic or private ports) that are not reserved by other services can be
used.
The default setting is to listen on all network interfaces (IP addresses) on port 80.
When the firewall is enabled, you can check whether to enable Apache ports on the
firewell.
Check Open Firewall for Selected Ports to open the ports in the firewall that the
Web server listens on. This is necessary to make the Web server available on the
network, which can be a LAN, WAN, or the public Internet. Keeping the Listen
port closed is useful in test situations where no external access to the Web server
is necessary. If you are satisfied with the default settings or if you have made any
changes, click Next to continue with configuration.
The Apache Web Server
681
Figure 46.1
HTTP Server Wizard: Network Device Selection
Modules
The SUSE Linux Apache package comes with a wide variety of Apache modules.
Modules extend Apache's functionality and are available for a wide range of tasks.
The Modules configuration option allows for the loading and unloading of various
Apache modules at when the server is started. For a more detailed explanation of
modules, refer to Section 46.5, “Apache Modules” (page 700). Click Next to continue.
682
Figure 46.2
HTTP Server Wizard: Modules
Default Host
This option pertains to the default Web server. As explained in Section 46.4, “Virtual Hosts” (page 696), Apache can serve multiple domains from a single physical
machine. The first declared domain (or VirtualHost) in the configuraton file is
commonly referred to as the Default Host. To edit the host settings, choose the appropriate entry in the table then click Edit. To add a new host, click Add. To delete
a host, select it and click Delete.
In this step, you can decide to add an SSL (secure sockets layer) option and value
to the host settings. You can read more about this in Section “Adding SSL Support”
(page 688).
The Apache Web Server
683
Figure 46.3
HTTP Server Wizard: Default Host
Here is list of the default settings of the server:
Document Root
As described in Section “Document Root” (page 679), /srv/www/htdocs is the
default location from which Apache serves Web pages.
Directory
/srv/www/htdocs is the location of the Web pages.
Alias
With the help of Alias directives, URLs can be mapped to physical file system
locations. This means that a certain path even outside the Document Root in the
file system can be accessed via a URL aliasing that path.
The default SUSE Linux Alias /icons points to /usr/share/apache2/
icons for the Apache icons displayed in the directory index view.
Directory
/usr/shareapache2/icons is the location of the Alias directory.
684
Script Alias
Similar to the Alias directive, the ScriptAlias directive maps a URL to a file
system location. The difference is that ScriptAlias designates the target directory as a CGI location, meaning that CGI scripts should be executed in that location.
Directory
/srv/www/cgi-bin is the location of the ScriptAlias directory.
Include
/etc/apache2/conf.d/*.conf is the directory containing the configuration
files that come with certain packages. /etc/apache2/conf.d/
apache2-manual?conf is the directory containing all apache2-manual
configuration files.
Server Resolution
This option refers to Section 46.4, “Virtual Hosts” (page 696).
Determine Request Server by HTTP Headers lets a VirtualHost answer on a
request to its server name (see Section 46.4.1, “Name-Based Virtual Hosts”
(page 696)).
Determine Request Server by Server IP Address makes Apache select the requested
host by the HTTP header information the client sends. See Section 46.4.2, “IP-Based
Virtual Hosts” (page 698) for more details on IP-based virtual hosts.
Server Name
This specifies the default URL used by clients to contact the Web server. Usa a
FQDN (see Domain (page 672)) to reach the Web server at http://FQDN or its
IP address.
Server Administrator E-Mail
Provide the Web server administrator's e-mail address for Server Administrator EMail.
After finishing with the Default Host step, click Next to continue with the configuration
dialog.
Virtual Hosts
In this step, the wizard displays a list of already configured virtual hosts (see Section 46.4, “Virtual Hosts” (page 696)). One of the hosts is marked as default (with
The Apache Web Server
685
an asterisk next to the server name). To set a default host, select the server and click
Set as Default.
To add a host, click Add and a dialog appears in which to enter basic information
about the host. Server Indentification includes the server name, server contents root,
and administrator e-mail. The help text in the left frame of the window explains
each of these items in detail. Server Resolution is used to determine how a host is
identified. You can specify whether to determine a request server from HTTP
headers or by server IP address by selecting the respective option. The other possibility is to determine the virtual host by the IP address used by the client when
connecting to the server. You can also choose to enable SSL support by checking
that option. The certificate file path can also be specified. By clicking Browse, the
default directory /etc/apache2/ssl.crt is displayed. After all information
has been entered, click Next to continue to the final step of configuration.
Figure 46.4
HTTP Server Wizard: Virtual Hosts
Summary
This is the final step of the wizard. Here, determine how and when the Apache
server is started: when booting or manually. The port selected earlier is also displayed
along with the default and virtual hosts. If you are satisfied with your settings, click
Finish to complete configuration.
686
Figure 46.5
HTTP Server Wizard: Summary
HTTP Server Expert Configuration
The HTTP Server module also lets you make even more adjustments to the configuration.
Click HTTP Server Expert Configuration to see more configuration options. The following changes can then be made:
Listen On
Selecting the Listen on setting and clicking Edit opens a new window in which you
can add, delete, or edit entries.
Modules
By selecting the Modules settings and clicking Edit, you can change the status of
Apache2 modules by clicking Toggle Status. Click Add Module to add a new module.
Default Host
Selecting Default Host and clicking Edit lets you edit host settings. You can also
add, edit, or delete options.
Hosts
By selecting Hosts and clicking Edit, you can add, delete, edit, or select a host as
the default.
The Apache Web Server
687
In all of the preceding dialogs, you can click Log Files to view the error log and access
log. Click OK to complete configuration and return to the YaST Control Center.
Adding SSL Support
To add an SSL option to the host, click Add from step three (default host) of the HTTP
Server Wizard. If your server has already been set up and you no longer have access
to the wizard, you can set up an SSL option by selecting Default Hosts from the HTTP
Server Configuration dialog or clicking Edit, and Add. In both cases, a pop-up window
appears in which you scroll to an SSL option and confirm with OK. You are then asked
to enter a value for the option selected. This may be as simple as setting the value to
on or off, however, the dialog may require that you enter an appropriate value. If uncertain, refer to documentation for value parameters when configuring SSL. After you
click OK, the option and value appear in the host configuration list. Clicking Next takes
you to the next step in the configuration dialog.
If SSL appears in the host configuration list, click Edit to open the SSL configuration
dialog. If it is not displayed, click Add, selectSSL, and OK and the dialog opens automatically. Here, add, delete, or edit SSL options. Click OK to return to the HTTP
Server Wizard.
46.3.2 Configuring Apache Manually
Configuring Apache manually involves editing the plain text configuration files as the
user root.
IMPORTANT: No SuSEconfig Module for Apache2
The SuSEconfig module for Apache2 has been removed from SUSE Linux. It is
no longer necessary to run SuSEconfig after changing /etc/sysconfig/
apache2.
/etc/sysconfig/apache2
/etc/sysconfig/apache2 controls some global settings of Apache, like modules
to load, additional configuration files to include, flags with which the server should be
started, and flags that should be added to the command line. Every configuration option
688
in this file is extensively documented and therefore not mentioned here. For a generalpurpose Web server, /etc/sysconfig/apache2 should be sufficient for any
configuration needs. If a specific configuration is needed, refer to Section “Apache
Directives in /etc/apache2/httpd.conf: Global Environment ” (page 689).
IMPORTANT: Files Created Automatically on Server Start
/etc/sysconfig/apache2 creates or edits the following files automatically
when the Web server is started or restarted.
• /etc/apache2/sysconfig.d/loadmodule.conf—modules that are
loaded at runtime
• /etc/apache2/sysconfig.d/global.conf—serverwide general
settings
• /etc/apache2/sysconfig.d/include.conf—list of included configuration files
Do not edit these files manually. Instead, edit the corresponding settings in
/etc/sysconfig/apache2.
For fine-grained configuration tweaks, look at the files in /etc/apache2/*,
specifically for changes on manual configuration of virtual hosts, the global environment,
or the main server.
Apache Directives in /etc/apache2/httpd.conf: Global
Environment
SUSE Linux uses /etc/apache2/httpd.conf as a central point of reference for
other configuration files. Edit the file only to enable features that are not available in
/etc/sysconfig/apache2. The directives in the Global Environment section of
httpd.conf affect the overall operation of Apache.
The following sections describe some of the directives that are not available in YaST.
Core directives like Document Root (Document Root (page 684)) are essential and
required both in Global Environment and for VirtualHost.
The Apache Web Server
689
The following parameters and directives are ordered by logical affiliation and configuration scope. All of these should be set in /etc/apache2/httpd.conf.
LoadModule module_identifier /path/to/module
The LoadModule directive specifies an Apache module to load at runtime.
module_identifier is the name of the module according to its documentation.
/path/to/module can be an absolute or relative path pointing to the file.
Example 46.1
LoadModule Directive
LoadModule rewrite_module /usr/lib/apache2-prefork/mod_rewrite.so
On SUSE Linux, it is not necessary to use LoadModule statements directly. Instead,
APACHE_MODULE is used in /etc/sysconfig/apache2.
MaxClients number
The maximum number of clients Apache can handle concurrently. MaxClients must
be large enough to handle as many simultaneous requests as the Web site expects to
receive, but small enough to assure that there is enough physical RAM for all processes.
Timeout seconds
Specifies the time period Apache waits before reporting a time-out for a request.
Apache Directives in /etc/apache2/httpd.conf: Main
Server
The directives in the Main Server section apply when client requests are not handled
by any VirtualHost and therefore need to be processed by a default or main server.
Additionally, the parameters defined in this context are the defaults for all configured
virtual hosts. As a consequence, all of the directives in the Main Server can also
be set in the VirtualHost context, overwriting the defaults.
DirectoryIndex filenames
Set which files Apache should search to complete a URL lacking a file specification.
The default setting is index.html. For example, if the client requests the URL
690
http://www.example.com/foo/ and the directory foo contains a file called
index.html, Apache delivers this page to the client. Declare multiple files by separating them with spaces.
Example 46.2
DirectoryIndex Directive
DirectoryIndex index.html index.shtml start.php begin.pl
AllowOverride All | None | option
This directive can only be used inside a <Directory></Directory> declaration.
See Directory (page 684).
AllowOverride specifies what access and display options a .htaccess file (or
other files specified by AccessFileName as described in Section
“AccessFileName filenames ” (page 692)) can override.
Possible values are:
All
All options can be overridden by a .htaccess file.
None
No option can be overridden by a .htaccess file.
AuthConfig
Directories can be password protected with the help of a .htaccess file.
FileInfo
Allows the use of directives controlling document types within a .htaccess file.
A typical example for this is to configure custom error pages with ErrorDocument
(see http://httpd.apache.org/docs-2.0/mod/core.html
#errordocument).
Indexes
In the event that no DirectoryIndex document is found, this parameter allows
Apache to control the display of directory contents.
Limit
Controls access to a directory or to certain files for clients. The directives Allow,
Deny, and Order are used within a .htaccess file for this purpose. For usage
The Apache Web Server
691
of these directives, see the access module documentation (http://httpd
.apache.org/docs-2.0/mod/mod_access.html).
Options
Allow the usage of the Options and XBitHack directives within a .htaccess
file. The Options directive (http://httpd.apache.org/docs-2.0/
mod/core.html#options) controls which server features are available in a
particular directory. The XBitHack directive (http://httpd.apache.org/
docs-2.0/mod/mod_include.html#xbithack) allows files with the execute bit set to be parsed as SSI (see Section “Server-Side Includes with
mod_include ” (page 701)).
IMPORTANT
These settings are applied recursively to the current directory and its subdirectories. These options, except All and None, can be combined, separated by
spaces.
Example 46.3
AllowOverride Directive
<Directory /srv/www/htdocs>
AllowOverride None
</Directory>
<Directory /srv/www/htdocs/project>
AllowOverride All
</Directory>
<Directory /srv/www/htdocs/project/webapp>
AllowOverride Indexes Limit Auth