Virtualization Guide - The definitive guide for virtualization on Fedora

Fedora 12
Virtualization Guide
The definitive guide for virtualization on Fedora
Christoph Curran
Virtualization Guide
Fedora 12 Virtualization Guide
The definitive guide for virtualization on Fedora
Edition 1
Author
Christoph Curran
ccurran@redhat.com
Copyright © 2009 Red Hat, Inc.
The text of and illustrations in this document are licensed by Red Hat under a Creative Commons
Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available
at http://creativecommons.org/licenses/by-sa/3.0/. The original authors of this document, and Red Hat,
designate the Fedora Project as the "Attribution Party" for purposes of CC-BY-SA. In accordance with
CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the
original version.
Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert,
Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.
Red Hat, Red Hat Enterprise Linux, the Shadowman logo, JBoss, MetaMatrix, Fedora, the Infinity
Logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.
For guidelines on the permitted uses of the Fedora trademarks, refer to https://fedoraproject.org/wiki/
Legal:Trademark_guidelines.
Linux® is the registered trademark of Linus Torvalds in the United States and other countries.
Java® is a registered trademark of Oracle and/or its affiliates.
XFS® is a trademark of Silicon Graphics International Corp. or its subsidiaries in the United States
and/or other countries.
All other trademarks are the property of their respective owners.
The Fedora 12 Virtualization Guide contains information on installation, configuring, administering,
tips, tricks and troubleshooting virtualization technologies used in Fedora 12.
Preface
vii
1. About this book ............................................................................................................. vii
2. Document Conventions .................................................................................................. vii
2.1. Typographic Conventions .................................................................................... vii
2.2. Pull-quote Conventions ........................................................................................ ix
2.3. Notes and Warnings ............................................................................................ ix
3. We Need Feedback! ....................................................................................................... x
I. Installation
1
1. Installing the virtualization packages
3
1.1. Installing KVM with a new Fedora installation ......................................................... 3
1.2. Installing KVM packages on an existing Fedora system .......................................... 5
2. Virtualized guest installation overview
7
2.1. Creating guests with virt-install .............................................................................. 7
2.2. Creating guests with virt-manager ......................................................................... 7
2.3. Installing guests with PXE ................................................................................... 16
3. Guest operating system installation procedures
3.1. Installing Red Hat Enterprise Linux 5 as a para-virtualized guest ............................
3.2. Installing Red Hat Enterprise Linux as a fully virtualized guest ...............................
3.3. Installing Windows XP as a fully virtualized guest .................................................
3.4. Installing Windows Server 2003 as a fully virtualized guest ....................................
3.5. Installing Windows Server 2008 as a fully virtualized guest ....................................
II. Configuration
23
23
65
74
91
94
107
4. Virtualized block devices
4.1. Creating a virtualized floppy disk controller .........................................................
4.2. Adding storage devices to guests ......................................................................
4.3. Configuring persistent storage ...........................................................................
4.4. Add a virtualized CD-ROM or DVD device to a guest ..........................................
109
109
110
113
115
5. Shared storage and virtualization
5.1. Using iSCSI for storing guests ...........................................................................
5.2. Using NFS for storing guests ............................................................................
5.3. Using GFS2 for storing guests ..........................................................................
117
117
117
117
6. Server best practices
119
7. Security for virtualization
121
7.1. SELinux and virtualization ................................................................................. 121
7.2. SELinux considerations ..................................................................................... 122
8. Network Configuration
123
8.1. Network address translation (NAT) with libvirt ..................................................... 123
8.2. Bridged networking with libvirt ........................................................................... 124
9. KVM Para-virtualized Drivers
127
9.1. Installing the KVM Windows para-virtualized drivers ............................................ 127
III. Administration
10. Managing guests with xend
137
139
iii
Virtualization Guide
11. KVM guest timing management
141
12. KVM live migration
12.1. Live migration requirements ............................................................................
12.2. Share storage example: NFS for a simple migration ..........................................
12.3. Live KVM migration with virsh .........................................................................
12.4. Migrating with virt-manager .............................................................................
145
145
146
147
148
13. Remote management of virtualized guests
13.1. Remote management with SSH .......................................................................
13.2. Remote management over TLS and SSL .........................................................
13.3. Transport modes .............................................................................................
159
159
160
161
IV. Virtualization Reference Guide
165
14. Virtualization tools
167
15. Managing guests with virsh
169
16. Managing guests with the Virtual Machine Manager (virt-manager)
16.1. The open connection window ..........................................................................
16.2. The Virtual Machine Manager main window ......................................................
16.3. The Virtual Machine Manager details window ..................................................
16.4. Virtual Machine graphical console ...................................................................
16.5. Starting virt-manager .......................................................................................
16.6. Restoring a saved machine ............................................................................
16.7. Displaying guest details ..................................................................................
16.8. Status monitoring ............................................................................................
16.9. Displaying guest identifiers ..............................................................................
16.10. Displaying a guest's status ...........................................................................
16.11. Displaying virtual CPUs ................................................................................
16.12. Displaying CPU usage ..................................................................................
16.13. Displaying memory usage ............................................................................
16.14. Managing a virtual network ............................................................................
16.15. Creating a virtual network ..............................................................................
179
179
180
181
182
183
184
185
190
192
193
194
195
196
198
199
V. Tips and Tricks
17. Tips and tricks
17.1. Automatically starting guests ...........................................................................
17.2. Changing between the KVM and Xen hypervisors .............................................
17.2.1. Xen to KVM .........................................................................................
17.2.2. KVM to Xen .........................................................................................
17.3. Using qemu-img .............................................................................................
17.4. Overcommitting with KVM ...............................................................................
17.5. Modifying /etc/grub.conf ...................................................................................
17.6. Verifying virtualization extensions .....................................................................
17.7. Identifying guest type and implementation ........................................................
17.8. Generating a new unique MAC address ...........................................................
17.9. Very Secure ftpd ..........................................................................................
17.10. Configuring LUN Persistence .........................................................................
17.11. Disable SMART disk monitoring for guests .....................................................
17.12. Cloning guest configuration files ....................................................................
17.13. Duplicating an existing guest and its configuration file .....................................
iv
209
211
211
211
211
213
214
215
217
218
218
219
220
221
222
222
223
18. Creating custom libvirt scripts
225
18.1. Using XML configuration files with virsh ........................................................... 225
VI. Troubleshooting
227
19. Troubleshooting
229
19.1. Loop device errors .......................................................................................... 229
19.2. Enabling Intel VT and AMD-V virtualization hardware extensions in BIOS ............ 229
A. Additional resources
231
A.1. Online resources ...................................................................................................... 231
A.2. Installed documentation ............................................................................................ 231
B. Revision History
233
C. Colophon
235
Glossary
237
v
vi
Preface
This book is the Fedora 12 Virtualization Guide. The Guide covers all aspects of using and managing
virtualization on Fedora 12.
1. About this book
This book is divided into 7 parts:
• System Requirements
• Installation
• Configuration
• Administration
• Reference
• Tips and Tricks
• Troubleshooting
2. Document Conventions
This manual uses several conventions to highlight certain words and phrases and draw attention to
specific pieces of information.
1
In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts set. The
Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not,
alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes
the Liberation Fonts set by default.
2.1. Typographic Conventions
Four typographic conventions are used to call attention to specific words and phrases. These
conventions, and the circumstances they apply to, are as follows.
Mono-spaced Bold
Used to highlight system input, including shell commands, file names and paths. Also used to highlight
keycaps and key combinations. For example:
To see the contents of the file my_next_bestselling_novel in your current
working directory, enter the cat my_next_bestselling_novel command at the
shell prompt and press Enter to execute the command.
The above includes a file name, a shell command and a keycap, all presented in mono-spaced bold
and all distinguishable thanks to context.
Key combinations can be distinguished from keycaps by the hyphen connecting each part of a key
combination. For example:
Press Enter to execute the command.
1
https://fedorahosted.org/liberation-fonts/
vii
Preface
Press Ctrl+Alt+F1 to switch to the first virtual terminal. Press Ctrl+Alt+F7 to
return to your X-Windows session.
The first paragraph highlights the particular keycap to press. The second highlights two key
combinations (each a set of three keycaps with each set pressed simultaneously).
If source code is discussed, class names, methods, functions, variable names and returned values
mentioned within a paragraph will be presented as above, in mono-spaced bold. For example:
File-related classes include filesystem for file systems, file for files, and dir for
directories. Each class has its own associated set of permissions.
Proportional Bold
This denotes words or phrases encountered on a system, including application names; dialog box text;
labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:
Choose System → Preferences → Mouse from the main menu bar to launch Mouse
Preferences. In the Buttons tab, click the Left-handed mouse check box and click
Close to switch the primary mouse button from the left to the right (making the mouse
suitable for use in the left hand).
To insert a special character into a gedit file, choose Applications → Accessories
→ Character Map from the main menu bar. Next, choose Search → Find… from the
Character Map menu bar, type the name of the character in the Search field and click
Next. The character you sought will be highlighted in the Character Table. Doubleclick this highlighted character to place it in the Text to copy field and then click the
Copy button. Now switch back to your document and choose Edit → Paste from the
gedit menu bar.
The above text includes application names; system-wide menu names and items; application-specific
menu names; and buttons and text found within a GUI interface, all presented in proportional bold and
all distinguishable by context.
Mono-spaced Bold Italic or Proportional Bold Italic
Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or
variable text. Italics denotes text you do not input literally or displayed text that changes depending on
circumstance. For example:
To connect to a remote machine using ssh, type ssh username@domain.name at
a shell prompt. If the remote machine is example.com and your username on that
machine is john, type ssh john@example.com.
The mount -o remount file-system command remounts the named file
system. For example, to remount the /home file system, the command is mount -o
remount /home.
To see the version of a currently installed package, use the rpm -q package
command. It will return a result as follows: package-version-release.
Note the words in bold italics above — username, domain.name, file-system, package, version and
release. Each word is a placeholder, either for text you enter when issuing a command or for text
displayed by the system.
viii
Pull-quote Conventions
Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and
important term. For example:
Publican is a DocBook publishing system.
2.2. Pull-quote Conventions
Terminal output and source code listings are set off visually from the surrounding text.
Output sent to a terminal is set in mono-spaced roman and presented thus:
books
books_tests
Desktop
Desktop1
documentation
downloads
drafts
images
mss
notes
photos
scripts
stuff
svgs
svn
Source-code listings are also set in mono-spaced roman but add syntax highlighting as follows:
package org.jboss.book.jca.ex1;
import javax.naming.InitialContext;
public class ExClient
{
public static void main(String args[])
throws Exception
{
InitialContext iniCtx = new InitialContext();
Object
ref
= iniCtx.lookup("EchoBean");
EchoHome
home
= (EchoHome) ref;
Echo
echo
= home.create();
System.out.println("Created Echo");
System.out.println("Echo.echo('Hello') = " + echo.echo("Hello"));
}
}
2.3. Notes and Warnings
Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.
Note
Notes are tips, shortcuts or alternative approaches to the task at hand. Ignoring a note
should have no negative consequences, but you might miss out on a trick that makes your
life easier.
Important
Important boxes detail things that are easily missed: configuration changes that only
apply to the current session, or services that need restarting before an update will apply.
Ignoring a box labeled 'Important' won't cause data loss but may cause irritation and
frustration.
ix
Preface
Warning
Warnings should not be ignored. Ignoring warnings will most likely cause data loss.
3. We Need Feedback!
If you find a typographical error in this manual, or if you have thought of a way to make this manual
better, we would love to hear from you! Please submit a report in Bugzilla: http://bugzilla.redhat.com/
bugzilla/ against the product Fedora Documentation.
When submitting a bug report, be sure to mention the manual's identifier: virtualization-guide
If you have a suggestion for improving the documentation, try to be as specific as possible when
describing it. If you have found an error, please include the section number and some of the
surrounding text so we can find it easily.
x
Part I. Installation
Virtualization installation topics
These chapters describe setting up the host and installing virtualized guests with Fedora. It is
recommended to read these chapters carefully to ensure successful installation of virtualized guest
operating systems.
Chapter 1.
Installing the virtualization packages
1.1. Installing KVM with a new Fedora installation
This section covers installing virtualization tools and KVM package as part of a fresh Fedora 12
installation.
Need help installing?
The Fedora 12 Installation Guide (available from http://docs.fedoraproject.org) covers
installing Fedora 12 in detail.
1.
Start an interactive Fedora installation from the Fedora 12 Installation CD-ROM, DVD or PXE.
2.
Complete the other steps up to the package selection step.
Select the Virtualization package group and the Customize Now radio button.
3.
Select the KVM package group. Deselect the Virtualization package group. This selects the KVM
hypervisor, virt-manager, libvirt and virt-viewer for installation.
3
Chapter 1. Installing the virtualization packages
4.
4
Customize the packages (if required)
Customize the Virtualization group if you require other virtualization packages.
Installing KVM packages on an existing Fedora system
Press Close followed by Next to continue the installation.
Installing KVM packages with Kickstart files
This section describes how to use a Kickstart file to install Fedora with the KVM hypervisor packages.
Kickstart files allow for large, automated installations without a user manually installing each individual
system. The steps in this section will assist you in creating and using a Kickstart file to install Fedora
with the virtualization packages.
In the %packages section of your Kickstart file, append the following package group:
%packages
@kvm
More information on Kickstart files can be found on the Fedora Project website, http://
docs.fedoraproject.org, in the Fedora 12 Installation Guide.
1.2. Installing KVM packages on an existing Fedora system
The section describes the steps for installing the KVM hypervisor on a working Fedora 12 or newer.
Installing the KVM hypervisor with yum
To use virtualization on Fedora you require the kvm package. The kvm package contains the KVM
kernel module providing the KVM hypervisor on the default Linux kernel.
5
Chapter 1. Installing the virtualization packages
To install the kvm package, run:
# yum install kvm
Now, install additional virtualization management packages.
Recommended virtualization packages:
python-virtinst
Provides the virt-install command for creating virtual machines.
libvirt
libvirt is an API library for interacting with hypervisors. libvirt uses the xm virtualization
framework and the virsh command line tool to manage and control virtual machines.
libvirt-python
The libvirt-python package contains a module that permits applications written in the Python
programming language to use the interface supplied by the libvirt API.
virt-manager
virt-manager, also known as Virtual Machine Manager, provides a graphical tool for
administering virtual machines. It uses libvirt library as the management API.
Install the other recommended virtualization packages:
# yum install virt-manager libvirt libvirt-python python-virtinst
6
Chapter 2.
Virtualized guest installation overview
After you have installed the virtualization packages on the host system you can create guest operating
systems. This chapter describes the general processes for installing guest operating systems on
virtual machines. You can create guests using the New button in virt-manager or use the command
line interface virt-install. Both methods are covered by this chapter.
Detailed installation instructions are available for specific versions of Fedora, other Linux distributions,
Solaris and Windows. Refer to Chapter 3, Guest operating system installation procedures for those
procedures.
2.1. Creating guests with virt-install
You can use the virt-install command to create virtualized guests from the command line.
virt-install is used either interactively or as part of a script to automate the creation of virtual
machines. Using virt-install with Kickstart files allows for unattended installation of virtual
machines.
The virt-install tool provides a number of options one can pass on the command line. To see a
complete list of options run:
$ virt-install --help
The virt-install man page also documents each command option and important variables.
qemu-img is a related command which may be used before virt-install to configure storage
options.
An important option is the --vnc option which opens a graphical window for the guest's installation.
This example creates a Red Hat Enterprise Linux 3 guest, named rhel3support, from a CD-ROM,
with virtual networking and with a 5 GB file-based block device image. This example uses the KVM
hypervisor.
# virt-install --accelerate --hvm --connect qemu:///system \
--network network:default \
--name rhel3support --ram=756\
--file=/var/lib/libvirt/images/rhel3support.img \
--file-size=6 --vnc --cdrom=/dev/sr0
Example 2.1. Using virt-install with KVM to create a Red Hat Enterprise Linux 3 guest
# virt-install --name Fedora11 --ram 512 --file=/var/lib/libvirt/images/Fedora11.img \
--file-size=3 --vnc --cdrom=/var/lib/libvirt/images/Fedora11.iso
Example 2.2. Using virt-install to create a Fedora 11 guest
2.2. Creating guests with virt-manager
virt-manager, also known as Virtual Machine Manager, is a graphical tool for creating and
managing virtualized guests.
7
Chapter 2. Virtualized guest installation overview
Procedure 2.1. Creating a virtualized guest with virt-manager
1. To start virt-manager run the following command as root:
# virt-manager &
The virt-manager command opens a graphical user interface window. Various functions are
not available to users without root privileges or sudo configured, including the New button and
you will not be able to create a new virtualized guest.
2.
Open the File -> Open Connection. The dialog box below appears. . Select a hypervisor and
click the Connect button:
3.
The virt-manager window allows you to create a new virtual machine. Click the New button to
create a new guest. This opens the wizard shown in the screenshot.
8
Creating guests with virt-manager
4.
The Create a new virtual system window provides a summary of the information you must
provide in order to create a virtual machine:
9
Chapter 2. Virtualized guest installation overview
Review the information for your installation and click the Forward button.
5.
The Choosing a virtualization method window appears. Choose between Para-virtualized or
Fully virtualized.
Full virtualization requires a system with Intel® VT or AMD-V processor. If the virtualization
extensions are not present the fully virtualized radio button or the Enable kernel/hardware
acceleration will not be selectable. The Para-virtualized option will be grayed out if kernelxen is not the kernel running presently.
If you connected to a KVM hypervisor only full virtualization is available.
10
Creating guests with virt-manager
Choose the virtualization type and click the Next button.
6.
The Locating installation media prompt asks for the installation media for the type of installation
you selected. This screen is dependent on what was selected in the previous step.
a.
The para-virtualized installation requires an installation tree accessible using one of the
following network protocols: HTTP, FTP or NFS. The installation media URL must contain a
Fedora installation tree. This tree is hosted using NFS, FTP or HTTP. The network services
and files can be hosted using network services on the host or another mirror.
Using a CD-ROM or DVD image (tagged as an .iso file), mount the CD-ROM image and
host the mounted files with one of the mentioned protocols.
Alternatively, copy the installation tree from a Fedora mirror.
11
Chapter 2. Virtualized guest installation overview
b.
12
A fully virtualized guest installation require bootable installation DVDs, CD-ROMs or images
of bootable installation DVDs or CD-ROMs (with the .iso or .img file type) locally. Windows
installations use DVD, CD-ROM or .iso file. Many Linux and UNIX-like operating systems
use an .iso file to install a base system before finishing the installation with a network based
installation tree.
Creating guests with virt-manager
After selecting the appropriate installation media, click the Forward button.
7.
The Assigning storage space window displays. Choose a disk partition, LUN or create a file
based image for the guest storage.
The convention for file based images in Fedora is that all file based guest images are in the
/var/lib/xen/images/ directory. Other directory locations for file based images are
prohibited by SELinux. If you run SELinux in enforcing mode, refer to Section 7.1, “SELinux and
virtualization” for more information on installing guests.
Your guest storage image should be larger than the size of the installation, any additional
packages and applications, and the size of the guests swap file. The installation process will
choose the size of the guest's swap file based on size of the RAM allocated to the guest.
Allocate extra space if the guest needs additional space for applications or other data. For
example, web servers require additional space for log files.
13
Chapter 2. Virtualized guest installation overview
Choose the appropriate size for the guest on your selected storage type and click the Forward
button.
Note
It is recommend that you use the default directory for virtual machine images, /var/
lib/xen/images/. If you are using a different location (such as /xen/images/ in
this example) make sure it is added to your SELinux policy and relabeled before you
continue with the installation (later in the document you will find information on how to
modify your SELinux policy).
8.
The Allocate memory and CPU window displays. Choose appropriate values for the virtualized
CPUs and RAM allocation. These values affect the host's and guest's performance.
Guests require sufficient physical memory (RAM) to run efficiently and effectively. Choose a
memory value which suits your guest operating system and application requirements. Most
operating system require at least 512MB of RAM to work responsively. Remember, guests use
physical RAM. Running too many guests or leaving insufficient memory for the host system
results in significant usage of virtual memory. Virtual memory is significantly slower causing
14
Creating guests with virt-manager
degraded system performance and responsiveness. Ensure to allocate sufficient memory for all
guests and the host to operate effectively.
Assign sufficient virtual CPUs for the virtualized guest. If the guest runs a multithreaded
application assign the number of virtualized CPUs it requires to run most efficiently. Do not
assign more virtual CPUs than there are physical processors (or hyper-threads) available on
the host system. It is possible to over allocate virtual processors, however, over allocating has
a significant, negative affect on guest and host performance due to processor context switching
overheads.
9.
The ready to begin installation window presents a summary of all configuration information
you entered. Review the information presented and use the Back button to make changes, if
necessary. Once you are satisfied click the Finish button and to start the installation process.
15
Chapter 2. Virtualized guest installation overview
A VNC window opens showing the start of the guest operating system installation process.
This concludes the general process for creating guests with virt-manager. Chapter 3, Guest
operating system installation procedures contains step-by-step instructions to installing a variety of
common operating systems.
2.3. Installing guests with PXE
This section covers the steps required to install guests with PXE. PXE guest installation requires
a shared network device, also known as a network bridge. The procedures below cover creating a
bridge and the steps required to utilize it the bridge for a PXE installation.
1.
Create a new bridge
a. Create a new network script file in the /etc/sysconfig/network-scripts/ directory.
This example creates a file named ifcfg-installation which makes a bridge named
installation
# cd /etc/sysconfig/network-scripts/
# vim ifcfg-installation
DEVICE=installation
TYPE=Bridge
BOOTPROTO=dhcp
16
Installing guests with PXE
ONBOOT=yes
Warning
The line, TYPE=Bridge, is case-sensitive. It must have uppercase 'B' and lower
case 'ridge'.
b.
c.
Start the new bridge.
# ifup installation
There are no interfaces added to the new bridge yet. Use the brctl show command to view
details about network bridges on the system.
# brctl show
bridge name
installation
virbr0
bridge id
8000.000000000000
8000.000000000000
STP enabled
no
yes
interfaces
The virbr0 bridge is the default bridge used by libvirt for Network Address Translation
(NAT) on the default Ethernet device.
2.
Add an interface to the new bridge
Edit the configuration file for the interface. Add the BRIDGE parameter to the configuration file with
the name of the bridge created in the previous steps.
# Intel Corporation Gigabit Network Connection
DEVICE=eth1
BRIDGE=installation
BOOTPROTO=dhcp
HWADDR=00:13:20:F7:6E:8E
ONBOOT=yes
After editing the configuration file, restart networking or reboot.
# service network restart
Verify the interface is attached with the brctl show command:
# brctl show
bridge name
installation
virbr0
3.
bridge id
8000.001320f76e8e
8000.000000000000
STP enabled
no
yes
interfaces
eth1
Security configuration
Configure iptables to allow all traffic to be forwarded across the bridge.
# iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT
17
Chapter 2. Virtualized guest installation overview
# service iptables save
# service iptables restart
Disable iptables on bridges
Alternatively, prevent bridged traffic from being processed by iptables rules. In /
etc/sysctl.conf append the following lines:
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
Reload the kernel parameters configured with sysctl
# sysctl -p /etc/sysctl.conf
4.
Restart libvirt before the installation
Restart the libvirt daemon.
# service libvirtd reload
The bridge is configured, you can now begin an installation.
PXE installation with virt-install
For virt-install append the --network=bridge:BRIDGENAME installation parameter where
installation is the name of your bridge. For PXE installations use the --pxe parameter.
# virt-install --accelerate --hvm --connect qemu:///system \
--network=bridge:installation --pxe\
--name EL10 --ram=756 \
--vcpus=4
--os-type=linux --os-variant=rhel5
--file=/var/lib/libvirt/images/EL10.img \
Example 2.3. PXE installation with virt-install
PXE installation with virt-manager
The steps below are the steps that vary from the standard virt-manager installation procedures. For
the standard installations refer to Chapter 3, Guest operating system installation procedures.
1.
18
Select PXE
Select PXE as the installation method.
Installing guests with PXE
2.
Select the bridge
Select Shared physical device and select the bridge created in the previous procedure.
19
Chapter 2. Virtualized guest installation overview
3.
20
Start the installation
The installation is ready to start.
Installing guests with PXE
A DHCP request is sent and if a valid PXE server is found the guest installation processes will start.
21
22
Chapter 3.
Guest operating system installation
procedures
This chapter covers how to install various guest operating systems in a virtualized environment on
Fedora. To understand the basic processes, refer to Chapter 2, Virtualized guest installation overview.
3.1. Installing Red Hat Enterprise Linux 5 as a paravirtualized guest
This section describes how to install Red Hat Enterprise Linux 5 as a para-virtualized guest. Paravirtualization is a faster than full virtualization and supports all of the advantages of full virtualization.
Para-virtualization requires a special, supported kernel, the kernel-xen kernel.
Important note on para-virtualization
Para-virtualization only works with the Xen hypervisor. Para-virtualization does not work
with the KVM hypervisor.
Ensure you have root access before starting the installation.
This method installs Red Hat Enterprise Linux from a remote server. The installation instructions
presented in this section are similar to installing from the minimal installation live CD-ROM.
Create para-virtualized Red Hat Enterprise Linux 5 guests using virt-manager or virt-install. For
instructions on virt-manager, refer to the procedure in Section 2.2, “Creating guests with virtmanager”.
Create a para-virtualized guest with the command line based virt-install tool. The --vnc
option shows the graphical installation. The name of the guest in the example is rhel5PV, the disk
image file is rhel5PV.dsk and a local mirror of the Red Hat Enterprise Linux 5 installation tree
is ftp://10.1.1.1/trees/CentOS5-B2-Server-i386/. Replace those values with values
accurate for your system and network.
# virt-install -n rhel5PV -r 500 \
-f /var/lib/libvirt/images/rhel5PV.dsk -s 3 --vnc -p \
-l ftp://10.1.1.1/trees/CentOS5-B2-Server-i386/
Automating installation
Red Hat Enterprise Linux can be installed without a graphical interface or manual input.
Use Kickstart files to automate the installation process.
Using either method opens this window, displaying the initial boot phases of your guest:
23
Chapter 3. Guest operating system installation procedures
After your guest has completed its initial boot, the standard installation process for Red Hat Enterprise
Linux starts. For most systems the default answers are acceptable.
Procedure 3.1. Para-virtualized Red Hat Enterprise Linux guest installation procedure
1. Select the language and click OK.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
2.
Select the keyboard layout and click OK.
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Chapter 3. Guest operating system installation procedures
3.
26
Assign the guest's network address. Choose to use DHCP (as shown below) or a static IP
address:
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
4.
If you select DHCP the installation process will now attempt to acquire an IP address:
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Chapter 3. Guest operating system installation procedures
5.
If you chose a static IP address for your guest this prompt appears. Enter the details on the
guest's networking configuration:
a.
Enter a valid IP address. Ensure the IP address you enter can reach the server with the
installation tree.
b.
Enter a valid Subnet mask, default gateway and name server address.
Select the language and click OK.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
6.
This is an example of a static IP address configuration:
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Chapter 3. Guest operating system installation procedures
7.
30
The installation process now retrieves the files it needs from the server:
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Once the initial steps are complete the graphical installation process starts.
31
Chapter 3. Guest operating system installation procedures
If you are installing a Beta or early release distribution confirm that you want to install the operating
system. Click Install Anyway, and then click OK:
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Procedure 3.2. The graphical installation process
1. Enter a valid registration code. If you have a valid RHN subscription key please enter in the
Installation Number field:
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Chapter 3. Guest operating system installation procedures
Note
If you skip the registration step the you can confirm your fedora Network account
details after the installation with the rhn_register command. The rhn_register
command requires root access.
# rhn_register
2.
34
The installation prompts you to confirm erasure of all data on the storage you selected for the
installation:
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Yes to continue.
3.
Review the storage configuration and partition layout. You can chose to select the advanced
storage configuration if you want to use iSCSI for the guest's storage.
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Chapter 3. Guest operating system installation procedures
Make your selections then click Next.
4.
36
Confirm the selected storage for the installation.
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Yes to continue.
5.
Configure networking and hostname settings. These settings are populated with the data entered
earlier in the installation process. Change these settings if necessary.
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Chapter 3. Guest operating system installation procedures
Click OK to continue.
6.
38
Select the appropriate time zone for your environment.
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
7.
Enter the root password for the guest.
39
Chapter 3. Guest operating system installation procedures
Click Next to continue.
8.
40
Select the software packages to install. Select the Customize Now button. You must install
the kernel-xen package in the System directory. The kernel-xen package is required for paravirtualization.
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Next.
9.
Dependencies and space requirements are calculated.
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Chapter 3. Guest operating system installation procedures
10. After the installation dependencies and space requirements have been verified click Next to start
the actual installation.
42
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
11. All of the selected software packages are installed automatically.
43
Chapter 3. Guest operating system installation procedures
12. After the installation has finished reboot your guest:
44
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
13. The guest will not reboot, instead it will shutdown..
45
Chapter 3. Guest operating system installation procedures
14. Boot the guest. The guest's name was chosen when you used the virt-install in Section 3.1,
“Installing Red Hat Enterprise Linux 5 as a para-virtualized guest”. If you used the default example
the name is rhel5PV.
Run:
virsh reboot rhel5PV
Alternatively, open virt-manager, select the name of your guest, click Open, then click Run.
A VNC window displaying the guest's boot processes now opens.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
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Chapter 3. Guest operating system installation procedures
15. Booting the guest starts the First Boot configuration screen. This wizard prompts you for some
basic configuration choices for your guest.
48
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
16. Read and agree to the license agreement.
49
Chapter 3. Guest operating system installation procedures
Click Forward on the license agreement windows.
17. Configure the firewall.
50
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Forward to continue.
•
If you disable the firewall prompted to confirm your choice. Click Yes to confirm and continue.
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Chapter 3. Guest operating system installation procedures
18. Configure SELinux. It is strongly recommended you run SELinux in enforcing mode. You can
choose to either run SELinux in permissive mode or completely disable it.
52
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Forward to continue.
•
If you choose to disable SELinux this warning displays. Click Yes to disable SELinux.
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Chapter 3. Guest operating system installation procedures
19. Enable kdump if necessary.
54
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Forward to continue.
20. Confirm time and date are set correctly for your guest. If you install a para-virtualized guest time
and date should sync with the hypervisor.
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Chapter 3. Guest operating system installation procedures
Click Forward to continue.
21. Set up software updates. If you have a fedora Network subscription or want to trial one use the
screen below to register your newly installed guest in RHN.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click Forward to continue.
a.
Confirm your choices for RHN.
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Chapter 3. Guest operating system installation procedures
b.
58
Once setup has finished you may see one more screen if you opted out of RHN at this time.
You will not receive software updates.
Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
Click the Forward button.
22. Create a non root user account. It is advised to create a non root user for normal usage and
enhanced security. Enter the Username, Name and password.
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Chapter 3. Guest operating system installation procedures
Click the Forward button.
23. If a sound device is detected and you require sound, calibrate it. Complete the process and click
Forward.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
24. You can to install any additional software packages from CD you could do so on this screen. It it
often more efficient to not install any additional software at this point but add it later using yum.
Click Finish.
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Chapter 3. Guest operating system installation procedures
25. The guest now configure any settings you changed and continues the boot process.
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Installing Red Hat Enterprise Linux 5 as a para-virtualized guest
26. The Red Hat Enterprise Linux 5 login screen displays. Log in using the username created in the
previous steps.
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Chapter 3. Guest operating system installation procedures
27. You have now successfully installed a para-virtualized Red Hat Enterprise Linux 5 guest.
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Installing Red Hat Enterprise Linux as a fully virtualized guest
3.2. Installing Red Hat Enterprise Linux as a fully virtualized
guest
This section covers installing a fully virtualized Red Hat Enterprise Linux 5 guest.
Procedure 3.3. Creating a fully virtualized Red Hat Enterprise Linux 5 guest with virt-manager
1. Open virt-manager
Start virt-manager. Launch the Virtual Machine Manager application from the Applications
menu and System Tools submenu. Alternatively, run the virt-manager command as root.
2.
Select the hypervisor
Select the hypervisor. If installed, select Xen or KVM. For this example, select KVM. Note that
presently KVM is named qemu.
Connect to a hypervisor if you have not already done so. Open the File menu and select the Add
Connection... option. Refer to Section 16.1, “The open connection window”.
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Chapter 3. Guest operating system installation procedures
Once a hypervisor connection is selected the New button becomes available. Press the New
button.
3.
Start the new virtual machine wizard
Pressing the New button starts the virtual machine creation wizard.
Press Forward to continue.
4.
66
Name the virtual machine
Provide a name for your virtualized guest. Punctuation and whitespace characters are not
permitted.
Installing Red Hat Enterprise Linux as a fully virtualized guest
Press Forward to continue.
5.
Choose a virtualization method
Choose the virtualization method for the virtualized guest. Note you can only select an installed
virtualization method. If you selected KVM or Xen earlier (Step 4) you must use the hypervisor
you selected. This example uses the KVM hypervisor.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
6.
Select the installation method
Select Local install media for installing from an optical disc or ISO image; Network install tree
to install from a HTTP, FTP, or NFS server; or Network boot to install from a PXE server.
Set OS Type to Linux and OS Variant to Red Hat Enterprise Linux 5 as shown in the
screenshot.
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Installing Red Hat Enterprise Linux as a fully virtualized guest
Press Forward to continue.
7.
Locate installation media
Select ISO image location or CD-ROM or DVD device. This example uses an ISO file image of
the Red Hat Enterprise Linux 5 installation DVD.
a.
Press the Browse button.
b.
Search to the location of the ISO file and select the ISO image. Press Open to confirm your
selection.
c.
The file is selected and ready to install from.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
Image files and SELinux
For ISO image files and guest storage images, use the /var/lib/libvirt/
images/ directory. Any other location may require additional configuration for
SELinux, refer to Section 7.1, “SELinux and virtualization” for details.
8.
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Storage setup
Assign a physical storage device (Block device) or a file-based image (File). File-based images
must be stored in the /var/lib/libvirt/images/ directory. Assign sufficient storage for your
virtualized guest. Assign sufficient space for your virtualized guest and any application it requires.
Installing Red Hat Enterprise Linux as a fully virtualized guest
Press Forward to continue.
To migrating this guest
Live and offline migrations require guests to be installed on shared network storage.
For information on setting up shared storage for guests refer to Chapter 5, Shared
storage and virtualization.
9.
Network setup
Select either Virtual network or Shared physical device.
The virtual network option uses Network Address Translation (NAT) to share the default network
device with the virtualized guest. Use the virtual network option for wireless networks.
The shared physical device option uses a network bond to give the virtualized guest full access to
a network device.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
10. Memory and CPU allocation
The Allocate memory and CPU window displays. Choose appropriate values for the virtualized
CPUs and RAM allocation. These values affect the host's and guest's performance.
Virtualized guests require sufficient physical memory (RAM) to run efficiently and effectively.
Choose a memory value which suits your guest operating system and application requirements.
Windows Server 2008. Remember, guests use physical RAM. Running too many guests or
leaving insufficient memory for the host system results in significant usage of virtual memory
and swapping. Virtual memory is significantly slower causing degraded system performance
and responsiveness. Ensure to allocate sufficient memory for all guests and the host to operate
effectively.
Assign sufficient virtual CPUs for the virtualized guest. If the guest runs a multithreaded
application assign the number of virtualized CPUs it requires to run most efficiently. Do not
assign more virtual CPUs than there are physical processors (or hyper-threads) available on
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Installing Red Hat Enterprise Linux as a fully virtualized guest
the host system. It is possible to over allocate virtual processors, however, over allocating has
a significant, negative affect on guest and host performance due to processor context switching
overheads.
Press Forward to continue.
11. Verify and start guest installation
Verify the configuration.
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Chapter 3. Guest operating system installation procedures
Press Finish to start the guest installation procedure.
12. Installing Linux
Complete the Red Hat Enterprise Linux 5 installation sequence. The installation sequence is
covered by the Red Hat Enterprise Linux Installation Guide, available from http://redhat.com/docs.
A fully virtualized Red Hat Enterprise Linux 5 Guest is now installed.
3.3. Installing Windows XP as a fully virtualized guest
Windows XP can be installed as a fully virtualized guest. This section describes how to install
Windows XP as a fully virtualized guest on Linux.
Before commencing this procedure ensure you must have root access.
1.
74
Starting virt-manager
Open Applications > System Tools > Virtual Machine Manager. Open a connection to the host
(click File > Open Connection). Click the New button to create a new virtual machine.
Installing Windows XP as a fully virtualized guest
2.
Naming your virtual system
Enter the System Name and click the Forward button.
3.
Choosing a virtualization method
If you selected KVM or Xen earlier (step Step 1 ) you must use the hypervisor you selected. This
example uses the KVM hypervisor.
Windows can only be installed using full virtualization.
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Chapter 3. Guest operating system installation procedures
4.
Choosing an installation method
This screen enables you to specify the installation method and the type of operating system.
For CD-ROM or DVD installation select the device with the Windows installation disc in it. If you
chose ISO Image Location enter the path to a Windows installation .iso image.
Select Windows from the OS Type list and Microsoft Windows XP from the OS Variant list.
PXE installation is not covered by this chapter.
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Installing Windows XP as a fully virtualized guest
Press Forward to continue.
Image files and SELinux
For ISO image files and guest storage images the the recommended to use the /
var/lib/libvirt/images/ directory. Any other location may require additional
configuration for SELinux, refer to Section 7.1, “SELinux and virtualization” for details.
5.
The Assigning storage space window displays. Choose a disk partition, LUN or create a file
based image for the guest storage.
The convention for file based images in Fedora is that all file based guest images are in the /
var/lib/libvirt/images/ directory. Other directory locations for file based images are
prohibited by SELinux. If you run SELinux in enforcing mode, refer to Section 7.1, “SELinux and
virtualization” for more information on installing guests.
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Chapter 3. Guest operating system installation procedures
Your guest storage image should be larger than the size of the installation, any additional
packages and applications, and the size of the guests swap file. The installation process will
choose the size of the guest's swap file based on size of the RAM allocated to the guest.
Allocate extra space if the guest needs additional space for applications or other data. For
example, web servers require additional space for log files.
Choose the appropriate size for the guest on your selected storage type and click the Forward
button.
Note
It is recommend that you use the default directory for virtual machine images, /var/
lib/libvirt/images/. If you are using a different location (such as /images/ in
this example) make sure it is added to your SELinux policy and relabeled before you
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Installing Windows XP as a fully virtualized guest
continue with the installation (later in the document you will find information on how to
modify your SELinux policy)
6.
Network setup
Select either Virtual network or Shared physical device.
The virtual network option uses Network Address Translation (NAT) to share the default network
device with the virtualized guest. Use the virtual network option for wireless networks.
The shared physical device option uses a network bond to give the virtualized guest full access to
a network device.
Press Forward to continue.
7.
The Allocate memory and CPU window displays. Choose appropriate values for the virtualized
CPUs and RAM allocation. These values affect the host's and guest's performance.
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Chapter 3. Guest operating system installation procedures
Virtualized guests require sufficient physical memory (RAM) to run efficiently and effectively.
Choose a memory value which suits your guest operating system and application requirements.
Most operating system require at least 512MB of RAM to work responsively. Remember, guests
use physical RAM. Running too many guests or leaving insufficient memory for the host system
results in significant usage of virtual memory and swapping. Virtual memory is significantly slower
causing degraded system performance and responsiveness. Ensure to allocate sufficient memory
for all guests and the host to operate effectively.
Assign sufficient virtual CPUs for the virtualized guest. If the guest runs a multithreaded
application assign the number of virtualized CPUs it requires to run most efficiently. Do not
assign more virtual CPUs than there are physical processors (or hyper-threads) available on
the host system. It is possible to over allocate virtual processors, however, over allocating has
a significant, negative affect on guest and host performance due to processor context switching
overheads.
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Installing Windows XP as a fully virtualized guest
8.
Before the installation continues you will see the summary screen. Press Finish to proceed to the
guest installation:
9.
You must make a hardware selection so open a console window quickly after the installation
starts. Click Finish then switch to the virt-manager summary window and select your newly
started Windows guest. Double click on the system name and the console window opens. Quickly
and repeatedly press F5 to select a new HAL, once you get the dialog box in the Windows install
select the 'Generic i486 Platform' tab (scroll through selections with the Up and Down
arrows.
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Chapter 3. Guest operating system installation procedures
10. The installation continues with the standard Windows installation.
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Installing Windows XP as a fully virtualized guest
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Chapter 3. Guest operating system installation procedures
11. Partition the hard drive when prompted.
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Installing Windows XP as a fully virtualized guest
12. After the drive is formatted Windows starts copying the files to the hard drive.
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Chapter 3. Guest operating system installation procedures
13. The files are copied to the storage device, Windows now reboots.
14. Restart your Windows guest:
# virsh start WindowsGuest
Where WindowsGuest is the name of your virtual machine.
15. When the console window opens, you will see the setup phase of the Windows installation.
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Installing Windows XP as a fully virtualized guest
16. If your installation seems to get stuck during the setup phase, restart the guest with virsh
reboot WindowsGuestName. The will usually get the installation to continue. As you restart the
virtual machine you will see a Setup is being restarted message:
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Chapter 3. Guest operating system installation procedures
17. After setup has finished you will see the Windows boot screen:
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Installing Windows XP as a fully virtualized guest
18. Now you can continue with the standard setup of your Windows installation:
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Chapter 3. Guest operating system installation procedures
19. The setup process is complete, a Windows desktop displays.
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Installing Windows Server 2003 as a fully virtualized guest
3.4. Installing Windows Server 2003 as a fully virtualized
guest
This chapter describes installing a fully virtualized Windows Server 2003 guest with the virtinstall command. virt-install can be used instead of virt-manager This process is similar
to the Windows XP installation covered in Section 3.3, “Installing Windows XP as a fully virtualized
guest”.
1.
Using virt-install for installing Windows Server 2003 as the console for the Windows guest
opens the virt-viewer window promptly. An example of using the virt-install for installing a
Windows Server 2003 guest:
Start the installation with the virt-install command.
# virt-install -hvm -s 5 -f /var/lib/libvirt/images/windows2003spi1.dsk \
-n windows2003sp1 -cdrom=/ISOs/WIN/en_windows_server_2003_sp1.iso \
-vnc -r 1024
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Chapter 3. Guest operating system installation procedures
2.
Once the guest boots into the installation you must quickly press F5. If you do not press F5 at the
right time you will need to restart the installation. Pressing F5 allows you to select different HAL
or Computer Type. Choose Standard PC as the Computer Type. This is the only non standard
step required.
3.
Complete the rest of the installation.
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Installing Windows Server 2003 as a fully virtualized guest
4.
Windows Server 2003 is now installed as a fully virtualized guest.
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Chapter 3. Guest operating system installation procedures
3.5. Installing Windows Server 2008 as a fully virtualized
guest
This section covers installing a fully virtualized Windows Server 2008 guest.
Procedure 3.4. Installing Windows Server 2008 with virt-manager
1. Open virt-manager
Start virt-manager. Launch the Virtual Machine Manager application from the Applications
menu and System Tools submenu. Alternatively, run the virt-manager command as root.
2.
Select the hypervisor
Select the hypervisor. If installed, select Xen or KVM. For this example, select KVM. Note that
presently KVM is named qemu.
Once the option is selected the New button becomes available. Press the New button.
3.
94
Start the new virtual machine wizard
Pressing the New button starts the virtual machine creation wizard.
Installing Windows Server 2008 as a fully virtualized guest
Press Forward to continue.
4.
Name the virtual machine
Provide a name for your virtualized guest. Punctuation and whitespace characters are not
permitted.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
5.
96
Choose a virtualization method
Choose the virtualization method for the virtualized guest. Note you can only select an installed
virtualization method. If you selected KVM or Xen earlier (step 2) you must use the hypervisor you
selected. This example uses the KVM hypervisor.
Installing Windows Server 2008 as a fully virtualized guest
Press Forward to continue.
6.
Select the installation method
For all versions of Windows you must use local install media, either an ISO image or physical
optical media.
PXE may be used if you have a PXE server configured for Windows network installation. PXE
Windows installation is not covered by this guide.
Set OS Type to Windows and OS Variant to Microsoft Windows 2008 as shown in the
screenshot.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
7.
98
Locate installation media
Select ISO image location or CD-ROM or DVD device. This example uses an ISO file image of
the Windows Server 2008 installation CD.
a.
Press the Browse button.
b.
Search to the location of the ISO file and select it.
Installing Windows Server 2008 as a fully virtualized guest
Press Open to confirm your selection.
c.
The file is selected and ready to install from.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
Image files and SELinux
For ISO image files and guest storage images, the recommended directory to use
is the /var/lib/libvirt/images/ directory. Any other location may require
additional configuration for SELinux, refer to Section 7.1, “SELinux and virtualization”
for details.
8.
100
Storage setup
Assign a physical storage device (Block device) or a file-based image (File). File-based images
must be stored in the /var/lib/libvirt/images/ directory. Assign sufficient storage for your
virtualized guest. Assign sufficient space for your virtualized guest and any application it requires.
Installing Windows Server 2008 as a fully virtualized guest
Press Forward to continue.
9.
Network setup
Select either Virtual network or Shared physical device.
The virtual network option uses Network Address Translation (NAT) to share the default network
device with the virtualized guest. Use the virtual network option for wireless networks.
The shared physical device option uses a network bond to give the virtualized guest full access to
a network device.
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Chapter 3. Guest operating system installation procedures
Press Forward to continue.
10. Memory and CPU allocation
The Allocate memory and CPU window displays. Choose appropriate values for the virtualized
CPUs and RAM allocation. These values affect the host's and guest's performance.
Virtualized guests require sufficient physical memory (RAM) to run efficiently and effectively.
Choose a memory value which suits your guest operating system and application requirements.
Windows Server 2008. Remember, guests use physical RAM. Running too many guests or
leaving insufficient memory for the host system results in significant usage of virtual memory
and swapping. Virtual memory is significantly slower causing degraded system performance
and responsiveness. Ensure to allocate sufficient memory for all guests and the host to operate
effectively.
Assign sufficient virtual CPUs for the virtualized guest. If the guest runs a multithreaded
application assign the number of virtualized CPUs it requires to run most efficiently. Do not
assign more virtual CPUs than there are physical processors (or hyper-threads) available on
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Installing Windows Server 2008 as a fully virtualized guest
the host system. It is possible to over allocate virtual processors, however, over allocating has
a significant, negative affect on guest and host performance due to processor context switching
overheads.
Press Forward to continue.
11. Verify and start guest installation
Verify the configuration.
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Chapter 3. Guest operating system installation procedures
Press Finish to start the guest installation procedure.
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Installing Windows Server 2008 as a fully virtualized guest
12. Installing Windows
Complete the Windows Server 2008 installation sequence. The installation sequence is not
1
covered by this guide, refer to Microsoft's documentation for information on installing Windows.
105
106
Part II. Configuration
Configuring Virtualization in Fedora
These chapters cover configuration procedures for various advanced virtualization tasks. These tasks
include adding network and storage devices, enhancing security, improving performance, and using
the para-virtualized drivers on fully virtualized guests.
Chapter 4.
Virtualized block devices
This chapter covers installing and configuring block devices in virtualized guests. The term block
devices refers to various forms of storage devices.
4.1. Creating a virtualized floppy disk controller
Floppy disk controllers are required for a number of older operating systems, especially for installing
drivers. Presently, physical floppy disk devices cannot be accessed from virtualized guests. However,
creating and accessing floppy disk images from virtualized floppy drives is supported. This section
covers creating a virtualized floppy device.
An image file of a floppy disk is required. Create floppy disk image files with the dd command.
Replace /dev/fd0 with the name of a floppy device and name the disk appropriately.
# dd if=/dev/fd0 of=~/legacydrivers.img
Para-virtualized drivers note
The para-virtualized drivers can map physical floppy devices to fully virtualized guests.
This example uses a guest created with virt-manager running a fully virtualized Linux installation
with an image located in /var/lib/libvirt/images/rhel5FV.img. The Xen hypervisor is used
in the example.
1.
Create the XML configuration file for your guest image using the virsh command on a running
guest.
# virsh dumpxml rhel5FV > rhel5FV.xml
This saves the configuration settings as an XML file which can be edited to customize the
operations and devices used by the guest. For more information on using the virsh XML
configuration files, refer to Chapter 18, Creating custom libvirt scripts.
2.
Create a floppy disk image for the guest.
# dd if=/dev/zero of=/var/lib/libvirt/images/rhel5FV-floppy.img bs=512 count=2880
3.
Add the content below, changing where appropriate, to your guest's configuration XML file. This
example creates a guest with a floppy device as a file based virtual device.
<disk type='file' device='floppy'>
<source file='/var/lib/libvirt/images/rhel5FV-floppy.img'/>
<target dev='fda'/>
</disk>
4.
Stop the guest.
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Chapter 4. Virtualized block devices
# virsh stop rhel5FV
5.
Restart the guest using the XML configuration file.
# virsh create rhel5FV.xml
The floppy device is now available in the guest and stored as an image file on the host.
4.2. Adding storage devices to guests
This section covers adding storage devices to virtualized guest. Additional storage can only be added
after guests are created. The supported storage devices and protocol include:
• local hard drive partitions,
• logical volumes,
• Fibre Channel or iSCSI directly connected to the host.
• File containers residing in a file system on the host.
• NFS file systems mounted directly by the virtual machine.
• iSCSI storage directly accessed by the guest.
• Cluster File Systems (GFS).
Adding file based storage to a guest
File-based storage or file-based containers are files on the hosts file system which act as virtualized
hard drives for virtualized guests. To add a file-based container perform the following steps:
1.
Create an empty container file or using an existing file container (such as an ISO file).
a.
Create a sparse file using the dd command. Sparse files are not recommended due to data
integrity and performance issues. Sparse files are created much faster and can used for
testing but should not be used in production environments.
# dd if=/dev/zero of=/var/lib/libvirt/images/FileName.img bs=1M seek=4096 count=0
b.
Non-sparse, pre-allocated files are recommended for file based storage containers. Create a
non-sparse file, execute:
# dd if=/dev/zero of=/var/lib/libvirt/images/FileName.img bs=1M count=4096
Both commands create a 400MB file which can be used as additional storage for a virtualized
guest.
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Adding storage devices to guests
2.
Dump the configuration for the guest. In this example the guest is called Guest1 and the file is
saved in the users home directory.
# virsh dumpxml Guest1 > ~/Guest1.xml
3.
Open the configuration file (Guest1.xml in this example) in a text editor. Find the entries starting
with "disk=". This entry resembles:
>disk type='file' device='disk'<
>driver name='tap' type='aio'/<
>source file='/var/lib/libvirt/images/Guest1.img'/<
>target dev='xvda'/<
>/disk<
4.
Add the additional storage by modifying the end of disk= entry. Ensure you specify a device
name for the virtual block device which is not used already in the configuration file. The following
example entry adds file, named FileName.img, as a file based storage container:
>disk type='file' device='disk'<
>driver name='tap' type='aio'/<
>source file='/var/lib/libvirt/images/Guest1.img'/<
>target dev='xvda'/<
>/disk<
>disk type='file' device='disk'<
>driver name='tap' type='aio'/<
>source file='/var/lib/libvirt/images/FileName.img'/<
>target dev='hda'/<
>/disk<
5.
Restart the guest from the updated configuration file.
# virsh create Guest1.xml
6.
The following steps are Linux guest specific. Other operating systems handle new storage
devices in different ways. For non Linux systems refer to your guest operating systems
documentation.
The guest now uses the file FileName.img as the device called /dev/hdb. This device requires
formatting from the guest. On the guest, partition the device into one primary partition for the
entire device then format the device.
a.
Press n for a new partition.
# fdisk /dev/hdb
Command (m for help):
b.
Press p for a primary partition.
Command action
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Chapter 4. Virtualized block devices
e
p
c.
extended
primary partition (1-4)
Choose an available partition number. In this example the first partition is chosen by entering
1.
Partition number (1-4): 1
d.
Enter the default first cylinder by pressing Enter.
First cylinder (1-400, default 1):
e.
Select the size of the partition. In this example the entire disk is allocated by pressing Enter.
Last cylinder or +size or +sizeM or +sizeK (2-400, default 400):
f.
Set the type of partition by pressing t.
Command (m for help): t
g.
Choose the partition you created in the previous steps. In this example it's partition 1.
Partition number (1-4): 1
h.
Enter 83 for a Linux partition.
Hex code (type L to list codes): 83
i.
write changes to disk and quit.
Command (m for help): w
Command (m for help): q
j.
Format the new partition with the ext3 file system.
# mke2fs -j /dev/hdb
7.
Mount the disk on the guest.
# mount /dev/hdb1 /myfiles
The guest now has an additional virtualized file-based storage device.
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Configuring persistent storage
Adding hard drives and other block devices to a guest
System administrators use additional hard drives for to provide more storage space or to separate
system data from user data. This procedure, Procedure 4.1, “Adding physical block devices to
virtualized guests”, describes how to add a hard drive on the host to a virtualized guest.
The procedure works for all physical block devices, this includes CD-ROM, DVD and floppy devices.
Procedure 4.1. Adding physical block devices to virtualized guests
1. Physically attach the hard disk device to the host. Configure the host if the drive is not accessible
by default.
2.
Configure the device with multipath and persistence on the host if required.
3.
Use the virsh attach command. Replace: myguest with your guest's name, /dev/hdb1
with the device to add, and hdc with the location for the device on the guest. The hdc must be an
unused device name. Use the hd* notation for Windows guests as well, the guest will recognize
the device correctly.
Append the --type hdd parameter to the command for CD-ROM or DVD devices.
Append the --type floppy parameter to the command for floppy devices.
# virsh attach-disk myguest /dev/hdb1 hdc --driver tap --mode readonly
4.
The guest now has a new hard disk device called /dev/hdb on Linux or D: drive, or similar,
on Windows. This device may require formatting.
4.3. Configuring persistent storage
This section is for systems with external or networked storage; that is, Fibre Channel or iSCSI based
storage devices. It is recommended that those systems have persistent device names configured for
your hosts. This assists live migration as well as providing consistent device names and storage for
multiple virtualized systems.
Universally Unique Identifiers(UUIDs) are a standardized method for identifying computers and
devices in distributed computing environments. This sections uses UUIDs to identify iSCSI or Fibre
Channel LUNs. UUIDs persist after restarts, disconnection and device swaps. The UUID is similar to a
label on the device.
Systems which are not running multipath must use Single path configuration. Systems running
multipath can use Multiple path configuration.
Single path configuration
This procedure implements LUN device persistence using udev. Only use this procedure for hosts
which are not using multipath.
1.
Edit the /etc/scsi_id.config file.
a.
Ensure the options=-b is line commented out.
# options=-b
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Chapter 4. Virtualized block devices
b.
Add the following line:
options=-g
This option configures udev to assume all attached SCSI devices return a UUID.
2.
To display the UUID for a given device run the scsi_id -g -s /block/sd* command. For
example:
# scsi_id -g -s /block/sd*
3600a0b800013275100000015427b625e
The output may vary from the example above. The output displays the UUID of the device /dev/
sdc.
3.
Verify the UUID output by the scsi_id -g -s /block/sd* command is identical from
computer which accesses the device.
4.
Create a rule to name the device. Create a file named 20-names.rules in the /etc/udev/
rules.d directory. Add new rules to this file. All rules are added to the same file using the same
format. Rules follow this format:
KERNEL="sd*", BUS="scsi", PROGRAM="/sbin/scsi_id -g -s", RESULT=UUID, NAME=devicename
Replace UUID and devicename with the UUID retrieved above, and a name for the device. This
is a rule for the example above:
KERNEL="sd*", BUS="scsi", PROGRAM="/sbin/scsi_id -g -s",
RESULT="3600a0b800013275100000015427b625e", NAME="rack4row16"
The udev daemon now searches all devices named /dev/sd* for the UUID in the rule. Once
a matching device is connected to the system the device is assigned the name from the rule. In
the a device with a UUID of 3600a0b800013275100000015427b625e would appear as /dev/
rack4row16.
5.
Append this line to /etc/rc.local:
/sbin/start_udev
6.
Copy the changes in the /etc/scsi_id.config, /etc/udev/rules.d/20-names.rules,
and /etc/rc.local files to all relevant hosts.
/sbin/start_udev
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Add a virtualized CD-ROM or DVD device to a guest
Networked storage devices with configured rules now have persistent names on all hosts where the
files were updated This means you can migrate guests between hosts using the shared storage and
the guests can access the storage devices in their configuration files.
Multiple path configuration
The multipath package is used for systems with more than one physical path from the computer
to storage devices. multipath provides fault tolerance, fail-over and enhanced performance for
network storage devices attached to Linux systems.
Implementing LUN persistence in a multipath environment requires defined alias names for your
multipath devices. Each storage device has a UUID which acts as a key for the aliased names. Identify
a device's UUID using the scsi_id command.
# scsi_id -g -s /block/sdc
The multipath devices will be created in the /dev/mpath directory. In the example below 4 devices
are defined in /etc/multipath.conf:
multipaths {
multipath {
wwid 3600805f30015987000000000768a0019
alias oramp1
}
multipath {
wwid 3600805f30015987000000000d643001a
alias oramp2
}
mulitpath {
wwid 3600805f3001598700000000086fc001b
alias oramp3
}
mulitpath {
wwid 3600805f300159870000000000984001c
alias oramp4
}
}
This configuration will create 4 LUNs named /dev/mpath/oramp1, /dev/mpath/oramp2, /dev/
mpath/oramp3 and /dev/mpath/oramp4. Once entered, the mapping of the devices' WWID to
their new names are now persistent after rebooting.
4.4. Add a virtualized CD-ROM or DVD device to a guest
To attach an ISO file to a guest while the guest is online use virsh with the attach-disk
parameter.
# virsh attach-disk [domain-id] [source] [target] --driver file --type cdrom --mode readonly
The source and target parameters are paths for the files and devices, on the host and guest
respectively. The source parameter can be a path to an ISO file or the device from the /dev
directory.
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Chapter 5.
Shared storage and virtualization
This chapter covers using shared, networked storage with virtualization on Fedora.
The following methods are supported for virtualization:
• Fibre Channel
• iSCSI
• NFS
• GFS2
Networked storage is essential for live and offline guest migrations. You cannot migrate guests without
shared storage.
5.1. Using iSCSI for storing guests
This section covers using iSCSI-based devices to store virtualized guests.
5.2. Using NFS for storing guests
This section covers using NFS to store virtualized guests.
5.3. Using GFS2 for storing guests
This section covers using the fedora Global File System 2 (GFS2) to store virtualized guests.
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Chapter 6.
Server best practices
The following tasks and tips can assist you with securing and ensuring reliability of your Fedora server
host (dom0).
• Run SELinux in enforcing mode. You can do this by executing the command below.
# setenforce 1
• Remove or disable any unnecessary services such as AutoFS, NFS, FTP, HTTP, NIS, telnetd,
sendmail and so on.
• Only add the minimum number of user accounts needed for platform management on the server
and remove unnecessary user accounts.
• Avoid running any unessential applications on your host. Running applications on the host may
impact virtual machine performance and can affect server stability. Any application which may crash
the server will also cause all virtual machines on the server to go down.
• Use a central location for virtual machine installations and images. Virtual machine images should
be stored under /var/lib/libvirt/images/. If you are using a different directory for your
virtual machine images make sure you add the directory to your SELinux policy and relabel it before
starting the installation.
• Installation sources, trees, and images should be stored in a central location, usually the location of
your vsftpd server.
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Chapter 7.
Security for virtualization
When deploying virtualization technologies on your corporate infrastructure, you must ensure that the
host cannot be compromised. The host, in the Xen hypervisor, is a privileged domain that handles
system management and manages all virtual machines. If the host is insecure, all other domains in the
system are vulnerable. There are several ways to enhance security on systems using virtualization.
You or your organization should create a Deployment Plan containing the operating specifications
and specifies which services are needed on your virtualized guests and host servers as well as what
support is required for these services. Here are a few security issues to consider while developing a
deployment plan:
• Run only necessary services on hosts. The fewer processes and services running on the host, the
higher the level of security and performance.
• Enable SELinux on the hypervisor. Read Section 7.1, “SELinux and virtualization” for more
information on using SELinux and virtualization.
• Use a firewall to restrict traffic to dom0. You can setup a firewall with default-reject rules that will
help secure attacks on dom0. It is also important to limit network facing services.
• Do not allow normal users to access dom0. If you do permit normal users dom0 access, you run
the risk of rendering dom0 vulnerable. Remember, dom0 is privileged, and granting unprivileged
accounts may compromise the level of security.
7.1. SELinux and virtualization
Security Enhanced Linux was developed by the NSA with assistance from the Linux community to
provide stronger security for Linux. SELinux limits an attackers abilities and works to prevent many
common security exploits such as buffer overflow attacks and privilege escalation. It is because of
these benefits that Fedora recommends all Linux systems should run with SELinux enabled and in
enforcing mode.
SELinux prevents guest images from loading if SELinux is enabled and the images are not in the
correct directory. SELinux requires that all guest images are stored in /var/lib/libvirt/images.
Adding LVM based storage with SELinux in enforcing mode
The following section is an example of adding a logical volume to a virtualized guest with SELinux
enabled. These instructions also work for hard drive partitions.
Procedure 7.1. Creating and mounting a logical volume on a virtualized guest with SELinux enabled
1. Create a logical volume. This example creates a 5 gigabyte logical volume named
NewVolumeName on the volume group named volumegroup.
# lvcreate -n NewVolumeName -L 5G volumegroup
2.
Format the NewVolumeName logical volume with a file system that supports extended attributes,
such as ext3.
# mke2fs -j /dev/volumegroup/NewVolumeName
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Chapter 7. Security for virtualization
3.
Create a new directory for mounting the new logical volume. This directory can be anywhere on
your file system. It is advised not to put it in important system directories (/etc, /var, /sys) or in
home directories (/home or /root). This example uses a directory called /virtstorage
# mkdir /virtstorage
4.
Mount the logical volume.
# mount /dev/volumegroup/NewVolumeName /virtstorage
5.
Set the correct SELinux type for the Xen folder.
semanage fcontext -a -t xen_image_t "/virtualization(/.*)?"
Alternatively, set the correct SELinux type for a KVM folder.
semanage fcontext -a -t virt_image_t "/virtualization(/.*)?"
If the targeted policy is used (targeted is the default policy) the command appends a line to the /
etc/selinux/targeted/contexts/files/file_contexts.local file which makes the
change persistent. The appended line may resemble this:
/virtstorage(/.*)?
6.
system_u:object_r:xen_image_t:s0
Run the command to change the type of the mount point (/virtstorage) and all files under it
to xen_image_t (restorecon and setfiles read the files in /etc/selinux/targeted/
contexts/files/).
# restorecon -R -v /virtualization
7.2. SELinux considerations
This sections contains things to you must consider when you implement SELinux into your
virtualization deployment. When you deploy system changes or add devices, you must update your
SELinux policy accordingly. To configure an LVM volume for a guest, you must modify the SELinux
context for the respective underlying block device and volume group.
# semanage fcontext -a -t xen_image _t -f -b /dev/sda2
# restorecon /dev/sda2
The Boolean parameter xend_disable_t can set the xend to unconfined mode after restarting the
daemon. It is better to disable protection for a single daemon than the whole system. It is advisable
that you should not re-label directories as xen_image_t that you will use elsewhere.
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Chapter 8.
Network Configuration
This page provides an introduction to the common networking configurations used by libvirt based
applications. This information applies to all hypervisors, whether Xen, KVM or another. For additional
information consult the libvirt network architecture docs.
The two common setups are "virtual network" or "shared physical device". The former is identical
across all distributions and available out-of-the-box. The latter needs distribution specific manual
configuration.
8.1. Network address translation (NAT) with libvirt
One of the most common methods for sharing network connections is to use Network address
translation (NAT) forwarding (also know as virtual networks).
Host configuration
Every standard libvirt installation provides NAT based connectivity to virtual machines out of the
box. This is the so called 'default virtual network'. Verify that it is available with the virsh net-list
--all command.
# virsh net-list --all
Name
State
Autostart
----------------------------------------default
active
yes
If it is missing, the example XML configuration file can be reloaded and activated:
# virsh net-define /usr/share/libvirt/networks/default.xml
The default network is defined from /usr/share/libvirt/networks/default.xml
Mark the default network to automatically start:
# virsh net-autostart default
Network default marked as autostarted
Start the default network:
# virsh net-start default
Network default started
Once the libvirt default network is running, you will see an isolated bridge device. This device does
not have any physical interfaces added, since it uses NAT and IP forwarding to connect to outside
world. Do not add new interfaces.
# brctl show
bridge name
bridge id
STP enabled
interfaces
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Chapter 8. Network Configuration
virbr0
8000.000000000000
yes
libvirt adds iptables rules which allow traffic to and from guests attached to the virbr0 device
in the INPUT, FORWARD, OUTPUT and POSTROUTING chains. libvirt then attempts to enable the
ip_forward parameter. Some other applications may disable ip_forward, so the best option is to
add the following to /etc/sysctl.conf.
net.ipv4.ip_forward = 1
Guest configuration
Once the host configuration is complete, a guest can be connected to the virtual network based on its
name. To connect a guest to the 'default' virtual network, the following XML can be used in the guest:
<interface type='network'>
<source network='default'/>
</interface>
Note
Defining a MAC address is optional. A MAC address is automatically generated if omitted.
Manually setting the MAC address is useful in certain situations.
<interface type='network'>
<source network='default'/>
<mac address='00:16:3e:1a:b3:4a'/>
</interface>
8.2. Bridged networking with libvirt
Bridged networking (also known as physical device sharing) is used for dedicating a physical device
to a virtual machine. Bridging is often used for more advanced setups and on servers with multiple
network interfaces.
Disable Xen network scripts
If your system was using a Xen bridge, it is recommended to disable the default Xen network bridge by
editing /etc/xen/xend-config.sxp and changing the line:
(network-script network-bridge)
To:
(network-script /bin/true)
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Bridged networking with libvirt
Disable NetworkManager
NetworkManager does not support bridging. NetworkManager must be disabled to use the older
network scripts networking.
#
#
#
#
chkconfig NetworkManager off
chkconfig network on
service NetworkManager stop
service network start
Note
Instead of turning off NetworkManager, you can add "NM_CONTROLLED=no" to the
ifcfg-* scripts used in the examples.
Creating network initscripts
Create or edit the following two network configuration files. This step can be repeated (with different
names) for additional network bridges.
Change to the /etc/sysconfig/network-scripts directory:
# cd /etc/sysconfig/network-scripts
Open the network script for the device you are adding to the bridge. In this example, ifcfg-eth0
defines the physical network interface which is set as part of a bridge:
DEVICE=eth0
# change the hardware address to match the hardware address your NIC uses
HWADDR=00:16:76:D6:C9:45
ONBOOT=yes
BRIDGE=br0
Tip
You can configure the device's Maximum Transfer Unit (MTU) by appending an MTU
variable to the end of the configuration file.
MTU=9000
Create a new network script in the /etc/sysconfig/network-scripts directory called ifcfgbr0 or similar. The br0 is the name of the bridge, this can be anything as long as the name of the file
is the same as the DEVICE parameter.
DEVICE=br0
TYPE=Bridge
BOOTPROTO=dhcp
ONBOOT=yes
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Chapter 8. Network Configuration
DELAY=0
Warning
The line, TYPE=Bridge, is case-sensitive. It must have uppercase 'B' and lower case
'ridge'.
After configuring, restart networking or reboot.
# service network restart
Configure iptables to allow all traffic to be forwarded across the bridge.
# iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT
# service iptables save
# service iptables restart
Disable iptables on bridges
Alternatively, prevent bridged traffic from being processed by iptables rules. In /etc/
sysctl.conf append the following lines:
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
Reload the kernel parameters configured with sysctl
# sysctl -p /etc/sysctl.conf
Restart the libvirt daemon.
# service libvirtd reload
You should now have a "shared physical device", which guests can be attached and have full LAN
access. Verify your new bridge:
# brctl show
bridge name
virbr0
br0
bridge id
8000.000000000000
8000.000e0cb30550
STP enabled
yes
no
interfaces
eth0
Note, the bridge is completely independent of the virbr0 bridge. Do not attempt to attach a physical
device to virbr0. The virbr0 bridge is only for Network Address Translation (NAT) connectivity.
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Chapter 9.
KVM Para-virtualized Drivers
Para-virtualized drivers are available for virtualized Windows guests running on KVM hosts. These
para-virtualized drivers are included in the virtio package. The virtio package supports block (storage)
devices and network interface controllers.
Para-virtualized drivers enhance the performance of fully virtualized guests. With the para-virtualized
drivers guest I/O latency decreases and throughput increases to near bare-metal levels. It is
recommended to use the para-virtualized drivers for fully virtualized guests running I/O heavy tasks
and applications.
The KVM para-virtualized drivers are automatically loaded and installed on newer versions of Fedora.
Those Fedora versions detect and install the drivers so additional installation steps are not required.
As with the KVM module, the virtio drivers are only available on hosts running newer versions of
Fedora.
Note
There are only 28 PCI slots available for additional devices per guest. Every paravirtualized network or block device uses one slot. Each guest can use up to 28 additional
devices made up of any combination of para-virtualized network, para-virtualized disk
devices, or other PCI devices using VTd.
The following Microsoft Windows versions have supported KVM para-virtualized drivers:
• Windows XP,
• Windows Server 2003,
• Windows Vista, and
• Windows Server 2008.
9.1. Installing the KVM Windows para-virtualized drivers
This section covers the installation process for the KVM Windows para-virtualized drivers. The KVM
para-virtualized drivers can be loaded during the Windows installation or installed after the guest is
installed.
You can install the para-virtualized drivers on your guest by one of the following methods:
• hosting the installation files on a network accessible to the guest,
• using a virtualized CD-ROM device of the driver installation disk .iso file, or
• using a virtualized floppy device to install the drivers during boot time (for Windows guests).
This guide describes installation from the para-virtualized installer disk as a virtualized CD-ROM
device.
1.
Download the drivers
1
The drivers are available from Microsoft (windowsservercatalog.com ).
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Chapter 9. KVM Para-virtualized Drivers
The virtio-win package installs a CD-ROM image, virtio-win.iso, in the /usr/share/
virtio-win/ directory.
2.
Install the para-virtualized drivers
It is recommended to install the drivers on the guest before attaching or modifying a device to use
the para-virtualized drivers.
For block devices storing root file systems or other block devices required for booting the guest,
the drivers must be installed before the device is modified. If the drivers are not installed on the
guest and the driver is set to the virtio driver the guest will not boot.
Mounting the image with virt-manager
Follow Procedure 9.1, “Using virt-manager to mount a CD-ROM image for a Windows guest” to
add a CD-ROM image with virt-manager.
Procedure 9.1. Using virt-manager to mount a CD-ROM image for a Windows guest
1. Open virt-manager, select your virtualized guest from the list of virtual machines and press the
Details button.
2.
Click the Add button in the Details panel.
3.
This opens a wizard for adding the new device. Select Storage device from the drop down menu,
then click Forward.
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Installing the KVM Windows para-virtualized drivers
4.
Choose the File (disk image) option and set the file location of the para-virtualized drivers .iso
file. The location of the .iso files is /usr/share/xenpv-win if you used yum to install the paravirtualized driver packages.
If the drivers are stored physical CD, use the Normal Disk Partition option.
Set the Device type to IDE cdrom and click Forward to proceed.
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Chapter 9. KVM Para-virtualized Drivers
5.
130
The disk has been assigned and is available for the guest once the guest is started. Click Finish
to close the wizard or back if you made a mistake.
Installing the KVM Windows para-virtualized drivers
Installing with a virtualized floppy disk
This procedure covers installing the para-virtualized drivers during a Windows installation.
•
Upon installing the Windows VM for the first time using the run-once menu attach viostor.vfd
as a floppy
a.
Windows Server 2003
When windows prompts to press F6 for third party drivers, do so and follow the onscreen
instructions.
b.
Windows Server 2008
When the installer prompts you for the driver, click on "Load Driver", point the installer to drive
A: and pick the driver that suits your OS and bittage
Using KVM para-virtualized drivers for existing devices
Modify an existing hard disk device attached to the guest to use the virtio driver instead of
virtualized IDE driver. This example edits libvirt configuration files. Alternatively, virt-manager,
virsh attach-disk or virsh attach-interface can add a new device using the paravirtualized drivers Using KVM para-virtualized drivers for new devices.
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Chapter 9. KVM Para-virtualized Drivers
1.
Below is a file-based block device using the virtualized IDE driver. This is a typical entry for a
virtualized guest not using the para-virtualized drivers.
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/disk1.img'/>
<target dev='hda' bus='ide'/>
</disk>
2.
Change the entry to use the para-virtualized device by modifying the bus= entry to virtio.
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/disk1.img'/>
<target dev='hda' bus='virtio'/>
</disk>
Using KVM para-virtualized drivers for new devices
This procedure covers creating new devices using the KVM para-virtualized drivers with virtmanager.
Alternatively, the virsh attach-disk or virsh attach-interface commands can be used to
attach devices using the para-virtualized drivers.
Install the drivers first
Ensure the drivers have been installed on the Windows guest before proceeding to install
new devices. If the drivers are unavailable the device will not be recognized and will not
work.
1.
Open the virtualized guest by double clicking on the name of the guest in virt-manager.
2.
Open the Hardware tab.
3.
Press the Add Hardware button.
4.
In the Adding Virtual Hardware tab select Storage or Network for the type of device.
1. New disk devices
Select the storage device or file based image. Select Virtio Disk as the Device type and
press Forward.
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Installing the KVM Windows para-virtualized drivers
2. New network devices
Select Virtual network or Shared physical device. Select virtio as the Device type and
press Forward.
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Chapter 9. KVM Para-virtualized Drivers
5.
134
Press Finish to save the device.
Installing the KVM Windows para-virtualized drivers
6.
Reboot the guest. The device may to be recognized by the Windows guest until it restarts.
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Part III. Administration
Administering virtualized systems
These chapters contain information for administering host and virtualized guests using tools included
in Fedora.
Chapter 10.
Managing guests with xend
The xend node control daemon performs certain system management functions that relate to virtual
machines. This daemon controls the virtualized resources, and xend must be running to interact with
virtual machines. Before you start xend, you must specify the operating parameters by editing the
xend configuration file /etc/xen/xend-config.sxp. Here are the parameters you can enable or
disable in the xend-config.sxp configuration file:
Item
Description
(console-limit)
Determines the console server's memory buffer
limit xend_unix_server and assigns values on a
per domain basis.
(min-mem)
Determines the minimum number of megabytes
that is reserved for domain0 (if you enter 0, the
value does not change).
(dom0-cpus)
Determines the number of CPUs in use by
domain0 (at least 1 CPU is assigned by default).
(enable-dump)
Determines that a crash occurs then enables a
dump (the default is 0).
(external-migration-tool)
Determines the script or application that handles
external device migration. Scripts must reside
in etc/xen/scripts/external-devicemigrate.
(logfile)
Determines the location of the log file (default is
/var/log/xend.log).
(loglevel)
Filters out the log mode values: DEBUG, INFO,
WARNING, ERROR, or CRITICAL (default is
DEBUG).
(network-script)
Determines the script that enables the
networking environment (scripts must reside in
etc/xen/scripts directory).
(xend-http-server)
Enables the http stream packet management
server (the default is no).
(xend-unix-server)
Enables the unix domain socket server, which is
a socket server is a communications endpoint
that handles low level network connections and
accepts or rejects incoming connections. The
default value is set to yes.
(xend-relocation-server)
Enables the relocation server for cross-machine
migrations (the default is no).
(xend-unix-path)
Determines the location where the xend-unixserver command outputs data (default is var/
lib/xend/xend-socket)
(xend-port)
Determines the port that the http management
server uses (the default is 8000).
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Chapter 10. Managing guests with xend
Item
Description
(xend-relocation-port)
Determines the port that the relocation server
uses (the default is 8002).
(xend-relocation-address)
Determines the host addresses allowed for
migration. The default value is the value of
xend-address.
(xend-address)
Determines the address that the domain socket
server binds to. The default value allows all
connections.
Table 10.1. xend configuration parameters
After setting these operating parameters, you should verify that xend is running and if not, initialize the
daemon. At the command prompt, you can start the xend daemon by entering the following:
service xend start
You can use xend to stop the daemon:
service xend stop
This stops the daemon from running.
You can use xend to restart the daemon:
service xend restart
The daemon starts once again.
You check the status of the xend daemon.
service xend status
The output displays the daemon's status.
Enabling xend at boot time
Use the chkconfig command to add the xend to the initscript.
chkconfig --level 345 xend
The the xend will now start at runlevels 3, 4 and 5.
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Chapter 11.
KVM guest timing management
KVM uses the constant Time Stamp Counter (TSC) feature of many modern CPUs. Some CPUs
do not have a constant Time Stamp Counter which will affect the way guests running on KVM keep
time. Guest's running without accurate timekeeping can have serious affects on some networked
applications as your guest will run faster or slower than the actual time.
Guests can have several problems caused by inaccurate clocks and counters:
• Clocks can fall out of synchronization with the actual time which invalidates sessions and affects
networks.
• Guests with slower clocks may have issues migrating.
• Guests may stop or crash.
These problems exist on other virtualization platforms and timing should always be tested.
NTP
The Network Time Protocol (NTP) daemon should be running on the host and the guests.
Enable the ntpd service:
# service ntpd start
Add the ntpd service to the default startup sequence:
# chkconfig ntpd on
Using the ntpd service should minimize the affects of clock skew in all cases.
Determining if your CPU has the constant Time Stamp Counter
Your CPU has a constant Time Stamp Counter if the constant_tsc flag is present. To determine if
your CPU has the constant_tsc flag run the following command:
$ cat /proc/cpuinfo | grep constant_tsc
If any output is given your CPU has the constant_tsc bit. If no output is given follow the instructions
below.
Configuring hosts without a constant Time Stamp Counter
Systems without constant time stamp counters require additional configuration. Power management
features interfere with accurate time keeping and must be disabled for guests to accurately keep time
with KVM.
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Chapter 11. KVM guest timing management
Note
These instructions are for AMD revision F cpus only.
1
If the CPU lacks the constant_tsc bit, disable all power management features (BZ#513138 ). Each
system has several timers it uses to keep time. The TSC is not stable on the host, which is sometimes
caused by cpufreq changes, deep C state, or migration to a host with a faster TSC. To stop deep C
states, which cam stop the TSC, add "processor.max_cstate=1" to the kernel boot options in grub
on the host:
term Fedora (vmlinuz-2.6.29.6-217.2.3.fc11)
root (hd0,0)
kernel /vmlinuz-vmlinuz-2.6.29.6-217.2.3.fc11 ro root=/dev/VolGroup00/LogVol00 rhgb
quiet processor.max_cstate=1
Disable cpufreq (only necessary on hosts without the constant_tsc) by editing the /etc/
sysconfig/cpuspeed configuration file and change the MIN_SPEED and MAX_SPEED variables
to the highest frequency available. Valid limits can be found in the /sys/devices/system/cpu/
cpu*/cpufreq/scaling_available_frequencies files.
Using the para-virtualized clock with Red Hat Enterprise Linux guests
For certain Red Hat Enterprise Linux guests, additional kernel parameters are required. These
parameters can be set by appending them to the end of the /kernel line in the /boot/grub/grub.conf file
of the guest.
The table below lists versions of Red Hat Enterprise Linux and the parameters required for guests on
systems without a constant Time Stamp Counter.
Red Hat Enterprise Linux
5.4 AMD64/Intel 64 with the
para-virtualized clock
1
Additional guest kernel parameters
Additional parameters are not required
5.4 AMD64/Intel 64 without the
para-virtualized clock
divider=10 notsc lpj=n
5.4 x86 with the para-virtualized
clock
Additional parameters are not required
5.4 x86 without the paravirtualized clock
divider=10 clocksource=acpi_pm lpj=n
5.3 AMD64/Intel 64
divider=10 notsc
5.3 x86
divider=10 clocksource=acpi_pm
4.8 AMD64/Intel 64
notsc divider=10
4.8 x86
clock=pmtmr divider=10
3.9 AMD64/Intel 64
Additional parameters are not required
3.9 x86
Additional parameters are not required
https://bugzilla.redhat.com/show_bug.cgi?id=513138
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Using the para-virtualized clock with Windows guests
Enable the para-virtualized clock on Window guests by editing the boot parameters. Windows boot
settings are stored in the boot.ini file. To enable the para-virtualized clock add the following line:
/use pmtimer
For more information on Windows boot settings and the pmtimer option, refer to Available switch
2
options for the Windows XP and the Windows Server 2003 Boot.ini files .
2
http://support.microsoft.com/kb/833721
143
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Chapter 12.
KVM live migration
This chapter covers migrating guests running on a KVM hypervisor to another KVM host.
Migration is name for the process of moving a virtualized guest from one host to another. Migration is a
key feature of virtualization as software is completely separated from hardware. Migration is useful for:
• Load balancing - guests can be moved to hosts with lower usage when a host becomes overloaded.
• Hardware failover - when hardware devices on the host start to fail, guests can be safely relocated
so the host can be powered down and repaired.
• Energy saving - guests can be redistributed to other hosts and host systems powered off to save
energy and cut costs in low usage periods.
• Geographic migration - guests can be moved to another location for lower latency or in serious
circumstances.
Migrations can be performed live or offline. To migrate guests the storage must be shared. Migration
works by sending the guests memory to the destination host. The shared storage stores the guest's
default file system. The file system image is not sent over the network from the source host to the
destination host.
An offline migration suspends the guest then moves an image of the guests memory to the destination
host. The guest is resumed on the destination host and the memory the guest used on the source host
is freed.
The time an offline migration takes depends network bandwidth and latency. A guest with 2GB of
memory should take an average of ten or so seconds on a 1 Gbit Ethernet link.
A live migration keeps the guest running on the source host and begins moving the memory without
stopping the guest. All modified memory pages are monitored for changes and sent to the destination
while the image is sent. The memory is updated with the changed pages. The process continues until
the amount of pause time allowed for the guest equals the predicted time for the final few pages to be
transfer. KVM estimates that and attempts to transfer the maximum amount of pages from the source
to the destination until we predict than the amount of remaining pages can be transferred in configured
time while the VM is paused. The registers are loaded on the new host and the guest is then resumed
on the destination host. If the guest is cannot be merged (which happens when guests are under
extreme loads) the guest is paused and then an offline migration is started instead.
The time an offline migration takes depends network bandwidth and latency. If the network is in heavy
use or a low bandwidth the migration will take much longer.
12.1. Live migration requirements
Migrating guests requires the following:
Migration requirements
• A virtualized guest installed on shared networked storage using one of the following protocols:
• Fibre Channel
• iSCSI
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Chapter 12. KVM live migration
• NFS
• GFS2
• Two or more Fedora systems of the same version with the same updates.
• Both system must have the appropriate ports open.
• Both systems must have identical network configurations. All bridging and network configurations
must be exactly the same on both hosts.
• Shared storage must mount at the same location on source and destination systems. The mounted
directory name must be identical.
Configuring network storage
Configure shared storage and install a guest on the shared storage. For shared storage instructions,
refer to Chapter 5, Shared storage and virtualization.
Alternatively, use the NFS example in Section 12.2, “Share storage example: NFS for a simple
migration”.
12.2. Share storage example: NFS for a simple migration
This example uses NFS to share guest images with other KVM hosts. This example is not practical for
large installations, this example is only for demonstrating migration techniques and small deployments.
Do not use this example for migrating or running more than a few virtualized guests.
For advanced and more robust shared storage instructions, refer to Chapter 5, Shared storage and
virtualization
1.
Export your libvirt image directory
Add the default image directory to the /etc/exports file:
/var/lib/libvirt/images *.bne.redhat.com(rw,no_root_squash,async)
Change the hosts parameter as required for your environment.
2.
Start NFS
a. Install the NFS packages if they are not yet installed:
# yum install nfs
b.
Open the ports for NFS in iptables and add NFS to the /etc/hosts.allow file.
c.
Start the NFS service:
# service nfs start
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Live KVM migration with virsh
3.
Mount the shared storage on the destination
On the destination system, mount the /var/lib/libvirt/images directory:
# mount sourceURL:/var/lib/libvirt/images /var/lib/libvirt/images
Locations must be the same on source and destination
Whichever directory is chosen for the guests must exactly the same on host and
guest. This applies to all types of shared storage. The directory must be the same or
the migration will fail.
12.3. Live KVM migration with virsh
A guest can be migrated to another host with the virsh command. The migrate command accepts
parameters in the following format:
# virsh migrate --live GuestName DestinationURL
The GuestName parameter represents the name of the guest which you want to migrate.
The DestinationURL parameter is the URL or hostname of the destination system. The destination
system must run the same version of Fedora, be using the same hypervisor and have libvirt
running.
Once the command is entered you will be prompted for the root password of the destination system.
Example: live migration with virsh
This example migrates from test1.bne.redhat.com to test2.bne.redhat.com. Change the
host names for your environment. This example migrates a virtual machine named CentOS4test.
This example assumes you have fully configured shared storage and meet all the prerequisites (listed
here: Migration requirements).
1.
Verify the guest is running
From the source system, test1.bne.redhat.com, verify CentOS4test is running:
[root@test1 ~]# virsh list
Id Name
State
---------------------------------10 CentOS4
running
2.
Migrate the guest
Execute the following command to live migrate the guest to the destination,
test2.bne.redhat.com. Append /system to the end of the destination URL to tell libvirt that
you need full access.
# virsh migrate --live CentOS4test qemu+ssh://test2.bne.redhat.com/system
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Chapter 12. KVM live migration
Once the command is entered you will be prompted for the root password of the destination
system.
3.
Wait
The migration may take some time depending on load and the size of the guest. virsh only
reports errors. The guest continues to run on the source host until fully migrated.
4.
Verify the guest has arrived at the destination host
From the destination system, test2.bne.redhat.com, verify CentOS4test is running:
[root@test2 ~]# virsh list
Id Name
State
---------------------------------10 CentOS4
running
The live migration is now complete.
Other networking methods
libvirt supports a variety of networking methods including TLS/SSL, unix sockets, SSH,
and unecrypted TCP. Refer to Chapter 13, Remote management of virtualized guests for
more information on using other methods.
12.4. Migrating with virt-manager
This section covers migrating KVM based guests with virt-manager.
1.
Connect to the source and target hosts. On the File menu, click Add Connection, the Add
Connection window appears.
Enter the following details:
• Hypervisor: Select QEMU.
• Connection: Select the connection type.
• Hostname: Enter the hostname.
Click Connect.
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Migrating with virt-manager
The Virtual Machine Manager displays a list of connected hosts.
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Chapter 12. KVM live migration
2.
Add a storage pool with the same NFS to the source and target hosts.
On the Edit menu, click Host Details, the Host Details window appears.
Click the Storage tab.
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Migrating with virt-manager
3.
Add a new storage pool. In the lower left corner of the window, click the + button. The Add a New
Storage Pool window appears.
Enter the following details:
• Name: Enter the name of the storage pool.
• Type: Select netfs: Network Exported Directory.
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Chapter 12. KVM live migration
Click Forward.
4.
Enter the following details:
• Format: Select the storage type. This must be NFS or iSCSI for live migrations.
• Host Name: Enter the IP address or fully-qualified domain name of the storage server.
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Migrating with virt-manager
Click Finish.
5.
Create a new volume in the shared storage pool, click New Volume.
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Chapter 12. KVM live migration
6.
Enter the details, then click Create Volume.
7.
Create a virtual machine with the new volume, then run the virtual machine.
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Migrating with virt-manager
The Virtual Machine window appears.
8.
In the Virtual Machine Manager window, right-click on the virtual machine, select Migrate, then
click the migration location.
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Chapter 12. KVM live migration
9.
Click Yes to confirm migration.
The Virtual Machine Manger displays the virtual machine in its new location.
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Migrating with virt-manager
The Virtual Machine window displays the new virtual machine location.
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Chapter 12. KVM live migration
158
Chapter 13.
Remote management of virtualized
guests
This section explains how to remotely manage your virtualized guests using ssh or TLS and SSL.
13.1. Remote management with SSH
The ssh package provides an encrypted network protocol which can securely send management
functions to remote virtualization servers. The method described uses the libvirt management
connection securely tunneled over an SSH connection to manage the remote machines. All the
authentication is done using SSH public key cryptography and passwords or passphrases gathered
by your local SSH agent. In addition the VNC console for each guest virtual machine is tunneled over
SSH.
SSH is usually configured by default so you probably already have SSH keys setup and no extra
firewall rules needed to access the management service or VNC console.
Be aware of the issues with using SSH for remotely managing your virtual machines, including:
• you require root log in access to the remote machine for managing virtual machines,
• the initial connection setup process may be slow,
• there is no standard or trivial way to revoke a user's key on all hosts or guests, and
• ssh does not scale well with larger numbers of remote machines.
Configuring SSH access for virt-manager
The following instructions assume you are starting from scratch and do not already have SSH keys set
up.
1. You need a public key pair on the machine virt-manager is used. If ssh is already configured
you can skip this command.
$ ssh-keygen -t rsa
2. To permit remote log in, virt-manager needs a copy of the public key on each remote machine
running libvirt. Copy the file $HOME/.ssh/id_rsa.pub from the machine you want to use for
remote management using the scp command:
$ scp $HOME/.ssh/id_rsa.pub root@somehost:/root/key-dan.pub
3. After the file has copied, use ssh to connect to the remote machines as root and add the file that
you copied to the list of authorized keys. If the root user on the remote host does not already have
an list of authorized keys, make sure the file permissions are correctly set
$ ssh root@somehost
# mkdir /root/.ssh
# chmod go-rwx /root/.ssh
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Chapter 13. Remote management of virtualized guests
# cat /root/key-dan.pub >> /root/.ssh/authorized_keys
# chmod go-rw /root/.ssh/authorized_keys
The libvirt daemon (libvirtd)
The libvirt daemon provide an interface for managing virtual machines. You should use the
libvirtd daemon installed and running on every remote host that you need to manage. Using the
Fedora kernel-xen package requires a speci TODO
$ ssh root@somehost
# chkconfig libvirtd on
# service libvirtd start
After libvirtd and SSH are configured you should be able to remotely access and manage your
virtual machines. You should also be able to access your guests with VNC at this point.
13.2. Remote management over TLS and SSL
You can manage virtual machines using TLS and SSL. TLS and SSL provides greater scalability but
is more complicated than ssh (refer to Section 13.1, “Remote management with SSH”). TLS and SSL
is the same technology used by web browsers for secure connections. The libvirt management
connection opens a TCP port for incoming connections, which is securely encrypted and authenticated
based on x509 certificates. In addition the VNC console for each guest virtual machine will be setup to
use TLS with x509 certificate authentication.
This method does not require shell accounts on the remote machines being managed. However, extra
firewall rules are needed to access the management service or VNC console. Certificate revocation
lists can revoke users' access.
Steps to setup TLS/SSL access for virt-manager
The following short guide assuming you are starting from scratch and you do not have any TLS/
SSL certificate knowledge. If you are lucky enough to have a certificate management server you can
probably skip the first steps.
libvirt server setup
For more information on creating certificates, refer to the libvirt website, http://libvirt.org/
remote.html.
Xen VNC Server
The Xen VNC server can have TLS enabled by editing the configuration file, /etc/xen/xendconfig.sxp. Remove the commenting on the (vnc-tls 1) configuration parameter in the
configuration file.
The /etc/xen/vnc directory needs the following 3 files:
• ca-cert.pem - The CA certificate
• server-cert.pem - The Server certificate signed by the CA
• server-key.pem - The server private key
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Transport modes
This provides encryption of the data channel. It might be appropriate to require that clients
present their own x509 certificate as a form of authentication. To enable this remove the
commenting on the (vnc-x509-verify 1) parameter.
virt-manager and virsh client setup
The setup for clients is slightly inconsistent at this time. To enable the libvirt management API
over TLS, the CA and client certificates must be placed in /etc/pki. For details on this consult
http://libvirt.org/remote.html
In the virt-manager user interface, use the 'SSL/TLS' transport mechanism option when
connecting to a host.
For virsh, the URI has the following format:
• qemu://hostname.guestname/system for KVM.
• xen://hostname.guestname/ for Xen.
To enable SSL and TLS for VNC, it is necessary to put the certificate authority and client certificates
into $HOME/.pki, that is the following three files:
• CA or ca-cert.pem - The CA certificate.
• libvirt-vnc or clientcert.pem - The client certificate signed by the CA.
• libvirt-vnc or clientkey.pem - The client private key.
13.3. Transport modes
For remote management, libvirt supports the following transport modes:
Transport Layer Security (TLS)
Transport Layer Security TLS 1.0 (SSL 3.1) authenticated and encrypted TCP/IP socket, usually
listening on a public port number. To use this you will need to generate client and server certificates.
The standard port is 16514.
UNIX sockets
Unix domain sockets are only accessible on the local machine. Sockets are not encrypted, and
use UNIX permissions or SELinux for authentication. The standard socket names are /var/
run/libvirt/libvirt-sock and /var/run/libvirt/libvirt-sock-ro (for read-only
connections).
SSH
Transported over an Secure Shell protocol (SSH) connection. Requires Netcat (the nc package)
installed. The libvirt daemon (libvirtd) must be running on the remote machine. Port 22 must be
open for SSH access. You should use some sort of ssh key management (for example, the sshagent utility) or you will be prompted for a password.
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Chapter 13. Remote management of virtualized guests
ext
The ext parameter is used for any external program which can make a connection to the remote
machine by means outside the scope of libvirt. This usually covers third-party, unsupported security
applications.
tcp
Unencrypted TCP/IP socket. Not recommended for production use, this is normally disabled, but an
administrator can enable it for testing or use over a trusted network. The default port is 16509.
The default transport, if no other is specified, is tls.
Remote URIs
A Uniform Resource Identifier (URI) is used by virsh and libvirt to connect
to a remote host. URIs can also be used with the --connect parameter for
the virsh command to execute single commands or migrations on remote hosts.
libvirt URIs take the general form (content in square brackets, "[]", represents optional functions):
driver[+transport]://[username@][hostname][:port]/[path][?extraparameters]
Either the transport method or the hostname must be provided in order to distinguish this from a local
URI.
Examples of remote management parameters
• Connect to a remote Xen hypervisor on the host named towada, using SSH transport and the SSH
username ccurran.
xen+ssh://ccurran@towada/
• Connect to a remote Xen hypervisor on the host named towada using TLS.
xen://towada/
• Connect to a remote Xen hypervisor on host towada using TLS. The no_verify=1 tells libvirt not
to verify the server's certificate.
xen://towada/?no_verify=1
• Connect to a remote KVM hypervisor on host towada using SSH.
qemu+ssh://towada/system
162
Transport modes
Testing examples
• Connect to the local KVM hypervisor with a non-standard UNIX socket. The full path to the Unix
socket is supplied explicitly in this case.
qemu+unix:///system?socket=/opt/libvirt/run/libvirt/libvirt-sock
• Connect to the libvirt daemon with an unencrypted TCP/IP connection to the server with the IP
address 10.1.1.10 on port 5000. This uses the test driver with default settings.
test+tcp://10.1.1.10:5000/default
Extra URI parameters
Extra parameters can be appended to remote URIs. The table below Table 13.1, “Extra URI
parameters” covers the recognized parameters. All other parameters are ignored. Note that parameter
values must be URI-escaped (that is, a question mark (?) is appended before the parameter and
special characters are converted into the URI format).
Name
Transport mode
Description
Example usage
name
all modes
The name passed
to the remote
virConnectOpen
function. The name
is normally formed by
removing transport,
hostname, port
number, username and
extra parameters from
the remote URI, but in
certain very complex
cases it may be better
to supply the name
explicitly.
name=qemu:///system
command
ssh and ext
The external
command. For ext
transport this is
required. For ssh the
default is ssh. The
PATH is searched for
the command.
command=/opt/
openssh/bin/ssh
socket
unix and ssh
The path to the UNIX
socket=/opt/libvirt/run/
domain socket, which
libvirt/libvirt-sock
overrides the default.
For ssh transport, this
is passed to the remote
netcat command (see
netcat).
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Chapter 13. Remote management of virtualized guests
Name
Transport mode
Description
Example usage
netcat
ssh
The name of the
netcat command on
the remote machine.
The default is nc.
For ssh transport,
libvirt constructs an
ssh command which
looks like: command
-p port [-l username]
hostname netcat -U
socket where port,
username, hostname
can be specified as
part of the remote URI,
and command, netcat
and socket come from
extra parameters (or
sensible defaults).
netcat=/opt/netcat/bin/
nc
no_verify
tls
If set to a non-zero
value, this disables
client checks of the
server's certificate.
Note that to disable
server checks of the
client's certificate or
IP address you must
change the libvirtd
configuration.
no_verify=1
no_tty
ssh
If set to a non-zero
value, this stops ssh
from asking for a
password if it cannot
log in to the remote
machine automatically
(for using ssh-agent
or similar). Use this
when you do not
have access to a
terminal - for example
in graphical programs
which use libvirt.
no_tty=1
Table 13.1. Extra URI parameters
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Part IV. Virtualization Reference Guide
Virtualization commands,
system tools, applications and
additional systems reference
These chapters provide detailed descriptions of virtualization commands, system tools, and
applications included in Fedora. These chapters are designed for users requiring information on
advanced functionality and other features.
Chapter 14.
Virtualization tools
The following is a list of tools for virtualization administration, debugging and networking tools that are
useful for systems running Xen.
System Administration Tools
• vmstat
• iostat
• lsof
# lsof -i :5900
xen-vncfb 10635
root
5u
IPv4 218738
TCP grumble.boston.redhat.com:5900 (LISTEN)
• qemu-img
Advanced Debugging Tools
• systemTap
• crash
• xen-gdbserver
• sysrq
• sysrq t
• sysrq w
• sysrq c
Networking
brtcl
•
# brctl show
bridge name bridge id
xenbr0
8000.feffffffffff
pdummy0
STP enabled
no
interfaces
vif13.0
vif0.0
•
•
# brctl showmacs xenbr0
port no mac addr
1
fe:ff:ff:ff:ff:ff
is local?
yes
# brctl showstp xenbr0
xenbr0
bridge id
8000.feffffffffff
designated root
8000.feffffffffff
root port
0
max age
20.00
hello time
2.00
aging timer
0.00
path cost
bridge max age
bridge hello time
0
20.00
2.00
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Chapter 14. Virtualization tools
forward delay
0.00
aging time
300.01
hello timer
1.43
topology change timer 0.00
flags
0.00
tcn timer
gc timer
0.00
0.02
vif13.0 (3)
port id
designated root
designated bridge
designated port
designated cost
flags
8003
8000.feffffffffff
8000.feffffffffff
8003
0
state
path cost
message age timer
forward delay timer
hold timer
forwarding
100
0.00
0.00
0.43
pdummy0 (2)
port id
designated root
designated bridge
designated port
designated cost
flags
8002
8000.feffffffffff
8000.feffffffffff
8002
0
state
path cost
message age timer
forward delay timer
hold timer
forwarding
100
0.00
0.00
0.43
vif0.0 (1)
port id
designated
designated
designated
designated
flags
8001
8000.feffffffffff
8000.feffffffffff
8001
0
state
path cost
message age timer
forward delay timer
hold timer
forwarding
100
0.00
0.00
0.43
• ifconfig
• tcpdump
KVM tools
• ps
• pstree
• top
• kvmtrace
• kvm_stat
Xen tools
• xentop
• xm dmesg
• xm log
168
bridge forward delay
root
bridge
port
cost
Chapter 15.
Managing guests with virsh
virsh is a command line interface tool for managing guests and the hypervisor.
The virsh tool is built on the libvirt management API and operates as an alternative to the xm
command and the graphical guest Manager (virt-manager). virsh can be used in read-only mode
by unprivileged users. You can use virsh to execute scripts for the guest machines.
virsh command quick reference
The following tables provide a quick reference for all virsh command line options.
Command
Description
help
Prints basic help information.
list
Lists all guests.
dumpxml
Outputs the XML configuration file for the guest.
create
Creates a guest from an XML configuration file
and starts the new guest.
start
Starts an inactive guest.
destroy
Forces a guest to stop.
define
Outputs an XML configuration file for a guest.
domid
Displays the guest's ID.
domuuid
Displays the guest's UUID.
dominfo
Displays guest information.
domname
Displays the guest's name.
domstate
Displays the state of a guest.
quit
Quits the interactive terminal.
reboot
Reboots a guest.
restore
Restores a previously saved guest stored in a
file.
resume
Resumes a paused guest.
save
Save the present state of a guest to a file.
shutdown
Gracefully shuts down a guest.
suspend
Pauses a guest.
undefine
Deletes all files associated with a guest.
migrate
Migrates a guest to another host.
Table 15.1. Guest management commands
The following virsh command options to manage guest and hypervisor resources:
Command
Description
setmem
Sets the allocated memory for a guest.
setmaxmem
Sets maximum memory limit for the hypervisor.
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Command
Description
setvcpus
Changes number of virtual CPUs assigned to a
guest.
vcpuinfo
Displays virtual CPU information about a guest.
vcpupin
Controls the virtual CPU affinity of a guest.
domblkstat
Displays block device statistics for a running
guest.
domifstat
Displays network interface statistics for a running
guest.
attach-device
Attach a device to a guest, using a device
definition in an XML file.
attach-disk
Attaches a new disk device to a guest.
attach-interface
Attaches a new network interface to a guest.
detach-device
Detach a device from a guest, takes the same
kind of XML descriptions as command attachdevice.
detach-disk
Detach a disk device from a guest.
detach-interface
Detach a network interface from a guest.
Table 15.2. Resource management options
These are miscellaneous virsh options:
Command
Description
version
Displays the version of virsh
nodeinfo
Outputs information about the hypervisor
Table 15.3. Miscellaneous options
Connecting to the hypervisor
Connect to a hypervisor session with virsh:
# virsh connect {hostname OR URL}
Where <name> is the machine name of the hypervisor. To initiate a read-only connection, append the
above command with -readonly.
Creating a virtual machine XML dump (configuration file)
Output a guest's XML configuration file with virsh:
# virsh dumpxml {domain-id, domain-name or domain-uuid}
This command outputs the guest's XML configuration file to standard out (stdout). You can save the
data by piping the output to a file. An example of piping the output to a file called guest.xml:
# virsh dumpxml GuestID > guest.xml
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This file guest.xml can recreate the guest (refer to Editing a guest's configuration file. You can edit
this XML configuration file to configure additional devices or to deploy additional guests. Refer to
Section 18.1, “Using XML configuration files with virsh” for more information on modifying files created
with virsh dumpxml.
An example of virsh dumpxml output:
# virsh dumpxml r5b2-mySQL01
<domain type='xen' id='13'>
<name>r5b2-mySQL01</name>
<uuid>4a4c59a7ee3fc78196e4288f2862f011</uuid>
<bootloader>/usr/bin/pygrub</bootloader>
<os>
<type>linux</type>
<kernel>/var/lib/libvirt/vmlinuz.2dgnU_</kernel>
<initrd>/var/lib/libvirt/initrd.UQafMw</initrd>
<cmdline>ro root=/dev/VolGroup00/LogVol00 rhgb quiet</cmdline>
</os>
<memory>512000</memory>
<vcpu>1</vcpu>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<interface type='bridge'>
<source bridge='xenbr0'/>
<mac address='00:16:3e:49:1d:11'/>
<script path='vif-bridge'/>
</interface>
<graphics type='vnc' port='5900'/>
<console tty='/dev/pts/4'/>
</devices>
</domain>
Creating a guest from a configuration file
Guests can be created from XML configuration files. You can copy existing XML from previously
created guests or use the dumpxml option (refer to Creating a virtual machine XML dump
(configuration file)). To create a guest with virsh from an XML file:
# virsh create configuration_file.xml
Editing a guest's configuration file
Instead of using the dumpxml option (refer to Creating a virtual machine XML dump (configuration
file)) guests can be edited either while they run or while they are offline. The virsh edit command
provides this functionality. For example, to edit the guest named softwaretesting:
# virsh edit softwaretesting
This opens a text editor. The default text editor is the $EDITOR shell parameter (set to vi by default).
Suspending a guest
Suspend a guest with virsh:
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# virsh suspend {domain-id, domain-name or domain-uuid}
When a guest is in a suspended state, it consumes system RAM but not processor resources. Disk
and network I/O does not occur while the guest is suspended. This operation is immediate and the
guest can be restarted with the resume (Resuming a guest) option.
Resuming a guest
Restore a suspended guest with virsh using the resume option:
# virsh resume {domain-id, domain-name or domain-uuid}
This operation is immediate and the guest parameters are preserved for suspend and resume
operations.
Save a guest
Save the current state of a guest to a file using the virsh command:
# virsh save {domain-name, domain-id or domain-uuid} filename
This stops the guest you specify and saves the data to a file, which may take some time given the
amount of memory in use by your guest. You can restore the state of the guest with the restore
(Restore a guest) option. Save is similar to pause, instead of just pausing a guest the present state of
the guest is saved.
Restore a guest
Restore a guest previously saved with the virsh save command (Save a guest) using virsh:
# virsh restore filename
This restarts the saved guest, which may take some time. The guest's name and UUID are preserved
but are allocated for a new id.
Shut down a guest
Shut down a guest using the virsh command:
# virsh shutdown {domain-id, domain-name or domain-uuid}
You can control the behavior of the rebooting guest by modifying the on_shutdown parameter in the
guest's configuration file file.
Rebooting a guest
Reboot a guest using virsh command:
#virsh reboot {domain-id, domain-name or domain-uuid}
You can control the behavior of the rebooting guest by modifying the on_reboot parameter in the
guest's configuration file file.
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Forcing a guest to stop
Force a guest to stop with the virsh command:
# virsh destroy {domain-id, domain-name or domain-uuid}
This command does an immediate ungraceful shutdown and stops the specified guest. Using
virsh destroy can corrupt guest file systems . Use the destroy option only when the guest is
unresponsive. For para-virtualized guests, use the shutdown option(Shut down a guest) instead.
Getting the domain ID of a guest
To get the domain ID of a guest:
# virsh domid {domain-name or domain-uuid}
Getting the domain name of a guest
To get the domain name of a guest:
# virsh domname {domain-id or domain-uuid}
Getting the UUID of a guest
To get the Universally Unique Identifier (UUID) for a guest:
# virsh domuuid {domain-id or domain-name}
An example of virsh domuuid output:
# virsh domuuid r5b2-mySQL01
4a4c59a7-ee3f-c781-96e4-288f2862f011
Displaying guest Information
Using virsh with the guest's domain ID, domain name or UUID you can display information on the
specified guest:
# virsh dominfo {domain-id, domain-name or domain-uuid}
This is an example of virsh dominfo output:
# virsh dominfo r5b2-mySQL01
id:
13
name:
r5b2-mysql01
uuid:
4a4c59a7-ee3f-c781-96e4-288f2862f011
os type:
linux
state:
blocked
cpu(s):
1
cpu time:
11.0s
max memory:
512000 kb
used memory:
512000 kb
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Displaying host information
To display information about the host:
# virsh nodeinfo
An example of virsh nodeinfo output:
# virsh nodeinfo
CPU model
CPU (s)
CPU frequency
CPU socket(s)
Core(s) per socket
Threads per core:
Numa cell(s)
Memory size:
x86_64
8
2895 Mhz
2
2
2
1
1046528 kb
This displays the node information and the machines that support the virtualization process.
Displaying the guests
To display the guest list and their current states with virsh:
# virsh list
Other options available include:
the --inactive option to list inactive guests (that is, guests that have been defined but are not
currently active), and
the --all option lists all guests. For example:
# virsh list --all
Id Name
State
---------------------------------0 Domain-0
running
1 Domain202
paused
2 Domain010
inactive
3 Domain9600
crashed
The output from virsh list is categorized as one of the six states (listed below).
• The running state refers to guests which are currently active on a CPU.
• Guests listed as blocked are blocked, and are not running or runnable. This is caused by a guest
waiting on I/O (a traditional wait state) or guests in a sleep mode.
• The paused state lists domains that are paused. This occurs if an administrator uses the pause
button in virt-manager, xm pause or virsh suspend. When a guest is paused it consumes
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memory and other resources but it is ineligible for scheduling and CPU resources from the
hypervisor.
• The shutdown state is for guests in the process of shutting down. The guest is sent a shutdown
signal and should be in the process of stopping its operations gracefully. This may not work with all
guest operating systems; some operating systems do not respond to these signals.
• Domains in the dying state are in is in process of dying, which is a state where the domain has not
completely shut-down or crashed.
• crashed guests have failed while running and are no longer running. This state can only occur if
the guest has been configured not to restart on crash.
Displaying virtual CPU information
To display virtual CPU information from a guest with virsh:
# virsh vcpuinfo {domain-id, domain-name or domain-uuid}
An example of virsh vcpuinfo output:
# virsh vcpuinfo r5b2-mySQL01
VCPU:
0
CPU:
0
State:
blocked
CPU time:
0.0s
CPU Affinity:
yy
Configuring virtual CPU affinity
To configure the affinity of virtual CPUs with physical CPUs:
# virsh vcpupin {domain-id, domain-name or domain-uuid} vcpu, cpulist
Where vcpu is the virtual VCPU number and cpulist lists the physical number of CPUs.
Configuring virtual CPU count
To modify the number of CPUs assigned to a guest with virsh:
# virsh setvcpus {domain-name, domain-id or domain-uuid} count
The new count value cannot exceed the count above the amount specified when the guest was
created.
Configuring memory allocation
To modify a guest's memory allocation with virsh :
# virsh setmem {domain-id or domain-name} count
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You must specify the count in kilobytes. The new count value cannot exceed the amount you specified
when you created the guest. Values lower than 64 MB are unlikely to work with most guest operating
systems. A higher maximum memory value will not affect the an active guest unless the new value is
lower which will shrink the available memory usage.
Displaying guest block device information
Use virsh domblkstat to display block device statistics for a running guest.
# virsh domblkstat GuestName block-device
Displaying guest network device information
Use virsh domifstat to display network interface statistics for a running guest.
# virsh domifstat GuestName interface-device
Migrating guests with virsh
A guest can be migrated to another host with virsh. Migrate domain to another host. Add --live for
live migration. The migrate command accepts parameters in the following format:
# virsh migrate --live GuestName DestinationURL
The --live parameter is optional. Add the --live parameter for live migrations.
The GuestName parameter represents the name of the guest which you want to migrate.
The DestinationURL parameter is the URL or hostname of the destination system. The destination
system must run the same version of Fedora, be using the same hypervisor and have libvirt
running.
Once the command is entered you will be prompted for the root password of the destination system.
Managing virtual networks
This section covers managing virtual networks with the virsh command. To list virtual networks:
# virsh net-list
This command generates output similar to:
# virsh net-list
Name
State
Autostart
----------------------------------------default
active
yes
vnet1
active
yes
vnet2
active
yes
To view network information for a specific virtual network:
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# virsh net-dumpxml NetworkName
This displays information about a specified virtual network in XML format:
# virsh net-dumpxml vnet1
<network>
<name>vnet1</name>
<uuid>98361b46-1581-acb7-1643-85a412626e70</uuid>
<forward dev='eth0'/>
<bridge name='vnet0' stp='on' forwardDelay='0' />
<ip address='192.168.100.1' netmask='255.255.255.0'>
<dhcp>
<range start='192.168.100.128' end='192.168.100.254' />
</dhcp>
</ip>
</network>
Other virsh commands used in managing virtual networks are:
• virsh net-autostart network-name — Autostart a network specified as network-name.
• virsh net-create XMLfile — generates and starts a new network using an existing XML file.
• virsh net-define XMLfile — generates a new network device from an existing XML file
without starting it.
• virsh net-destroy network-name — destroy a network specified as network-name.
• virsh net-name networkUUID — convert a specified networkUUID to a network name.
• virsh net-uuid network-name — convert a specified network-name to a network UUID.
• virsh net-start nameOfInactiveNetwork — starts an inactive network.
• virsh net-undefine nameOfInactiveNetwork — removes the definition of an inactive
network.
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Chapter 16.
Managing guests with the Virtual
Machine Manager (virt-manager)
This section describes the Virtual Machine Manager (virt-manager) windows, dialog boxes, and
various GUI controls.
virt-manager provides a graphical view of hypervisors and guest on your system and on remote
machines. You can use virt-manager to define both para-virtualized and fully virtualized guests.
virt-manager can perform virtualization management tasks, including:
• assigning memory,
• assigning virtual CPUs,
• monitoring operational performance,
• saving and restoring, pausing and resuming, and shutting down and starting virtualized guests,
• links to the textual and graphical consoles, and
• live and offline migrations.
16.1. The open connection window
This window appears first and prompts the user to choose a hypervisor session. Non-privileged users
can initiate a read-only session. Root users can start a session with full blown read-write status. For
normal use, select the Local Xen host option or QEMU (for KVM).
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Figure 16.1. Virtual Machine Manager connection window
16.2. The Virtual Machine Manager main window
This main window displays all the running virtual machines and resources currently allocated to them
(including domain0). You can decide which fields to display. Double-clicking on the desired virtual
machine brings up the respective console for that particular machine. Selecting a virtual machine and
double-click the Details button to display the Details window for that machine. You can also access
the File menu to create a new virtual machine.
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The Virtual Machine Manager details window
Figure 16.2. Virtual Machine Manager main window
16.3. The Virtual Machine Manager details window
This window displays graphs and statistics of a guest's live resource utilization data available from
virt-manager. The UUID field displays the globally unique identifier for the virtual machines.
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Figure 16.3. virt-manager details window
16.4. Virtual Machine graphical console
This window displays a virtual machine's graphical console. Para-virtualized and fully virtualized
guests use different techniques to export their local virtual framebuffers, but both technologies use
VNC to make them available to the Virtual Machine Manager's console window. If your virtual machine
is set to require authentication, the Virtual Machine Graphical console prompts you for a password
before the display appears.
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Starting virt-manager
Figure 16.4. Graphical console window
A note on security and VNC
VNC is considered insecure by many security experts, however, several changes have
been made to enable the secure usage of VNC for virtualization on Fedora. The guest
machines only listen to the local host (dom0)'s loopback address (127.0.0.1). This
ensures only those with shell privileges on the host can access virt-manager and the
virtual machine through VNC.
Remote administration can be performed following the instructions in Chapter 13, Remote
management of virtualized guests. TLS can provide enterprise level security for managing
guest and host systems.
Your local desktop can intercept key combinations (for example, Ctrl+Alt+F11) to prevent them from
being sent to the guest machine. You can use virt-managersticky key' capability to send these
sequences. You must press any modifier key (Ctrl or Alt) 3 times and the key you specify gets treated
as active until the next non-modifier key is pressed. Then you can send Ctrl-Alt-F11 to the guest by
entering the key sequence 'Ctrl Ctrl Ctrl Alt+F1'.
16.5. Starting virt-manager
To start virt-manager session open the Applications menu, then the System Tools menu and
select Virtual Machine Manager (virt-manager).
The virt-manager main window appears.
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Figure 16.5. Starting virt-manager
Alternatively, virt-manager can be started remotely using ssh as demonstrated in the following
command:
ssh -X host's address[remotehost]# virt-manager
Using ssh to manage virtual machines and hosts is discussed further in Section 13.1, “Remote
management with SSH”.
16.6. Restoring a saved machine
After you start the Virtual Machine Manager, all virtual machines on your system are displayed in
the main window. Domain0 is your host system. If there are no machines present, this means that
currently there are no machines running on the system.
To restore a previously saved session:
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Displaying guest details
1.
From the File menu, select Restore a saved machine.
Figure 16.6. Restoring a virtual machine
2.
The Restore Virtual Machine main window appears.
3.
Navigate to correct directory and select the saved session file.
4.
Click Open.
The saved virtual system appears in the Virtual Machine Manager main window.
Figure 16.7. A restored virtual machine manager session
16.7. Displaying guest details
You can use the Virtual Machine Monitor to view activity data information for any virtual machines on
your system.
To view a virtual system's details:
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Chapter 16. Managing guests with the Virtual Machine Manager (virt-manager)
1.
In the Virtual Machine Manager main window, highlight the virtual machine that you want to view.
Figure 16.8. Selecting a virtual machine to display
2.
From the Virtual Machine Manager Edit menu, select Machine Details (or click the Details button
on the bottom of the Virtual Machine Manager main window).
Figure 16.9. Displaying virtual machine details menu
The Virtual Machine Details Overview window appears. This window summarizes CPU and
memory usage for the domains you specified.
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Displaying guest details
Figure 16.10. Displaying guest details overview
3.
On the Virtual Machine Details window, click the Hardwaretab.
The Virtual Machine Details Hardware window appears.
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Figure 16.11. Displaying guest hardware details
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Displaying guest details
4.
On the Hardware tab, click on Processor to view or change the current processor allocation.
Figure 16.12. Processor allocation panel
5.
On the Hardware tab, click on Memory to view or change the current RAM memory allocation.
Figure 16.13. Displaying memory allocation
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Chapter 16. Managing guests with the Virtual Machine Manager (virt-manager)
6.
On the Hardware tab, click on Disk to view or change the current hard disk configuration.
Figure 16.14. Displaying disk configuration
7.
On the Hardware tab, click on Network to view or change the current network configuration.
Figure 16.15. Displaying network configuration
16.8. Status monitoring
You can use the Virtual Machine Manager to modify the virtual system Status monitoring.
To configure Status monitoring, and enable Consoles:
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Status monitoring
1.
From the Edit menu, select Preferences.
Figure 16.16. Modifying guest preferences
The Virtual Machine Manager Preferences window appears.
2.
From the Status monitoring area selection box, specify the time (in seconds) that you want the
system to update.
Figure 16.17. Configuring status monitoring
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Chapter 16. Managing guests with the Virtual Machine Manager (virt-manager)
3.
From the Consoles area, specify how to open a console and specify an input device.
16.9. Displaying guest identifiers
To view the guest IDs for all virtual machines on your system:
1.
From the View menu, select the Domain ID check box.
Figure 16.18. Viewing guest IDs
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Displaying a guest's status
2.
The Virtual Machine Manager lists the Domain IDs for all domains on your system.
Figure 16.19. Displaying domain IDs
16.10. Displaying a guest's status
To view the status of all virtual machines on your system:
1.
From the View menu, select the Status check box.
Figure 16.20. Selecting a virtual machine's status
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Chapter 16. Managing guests with the Virtual Machine Manager (virt-manager)
2.
The Virtual Machine Manager lists the status of all virtual machines on your system.
Figure 16.21. Displaying a virtual machine's status
16.11. Displaying virtual CPUs
To view the amount of virtual CPUs for all virtual machines on your system:
1.
From the View menu, select the Virtual CPUs check box.
Figure 16.22. Selecting the virtual CPUs option
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Displaying CPU usage
2.
The Virtual Machine Manager lists the Virtual CPUs for all virtual machines on your system.
Figure 16.23. Displaying Virtual CPUs
16.12. Displaying CPU usage
To view the CPU usage for all virtual machines on your system:
1.
From the View menu, select the CPU Usage check box.
Figure 16.24. Selecting CPU usage
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2.
The Virtual Machine Manager lists the percentage of CPU in use for all virtual machines on your
system.
Figure 16.25. Displaying CPU usage
16.13. Displaying memory usage
To view the memory usage for all virtual machines on your system:
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Displaying memory usage
1.
From the View menu, select the Memory Usage check box.
Figure 16.26. Selecting Memory Usage
2.
The Virtual Machine Manager lists the percentage of memory in use (in megabytes) for all virtual
machines on your system.
Figure 16.27. Displaying memory usage
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16.14. Managing a virtual network
To configure a virtual network on your system:
1.
From the Edit menu, select Host Details.
Figure 16.28. Selecting a host's details
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Creating a virtual network
2.
This will open the Host Details menu. Click the Virtual Networks tab.
Figure 16.29. Virtual network configuration
3.
All available virtual networks are listed on the left-hand box of the menu. You can edit the
configuration of a virtual network by selecting it from this box and editing as you see fit.
16.15. Creating a virtual network
To create a virtual network on your system:
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1.
Open the Host Details menu (refer to Section 16.14, “Managing a virtual network”) and click the
Add button.
Figure 16.30. Virtual network configuration
This will open the Create a new virtual network menu. Click Forward to continue.
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Creating a virtual network
Figure 16.31. Creating a new virtual network
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2.
Enter an appropriate name for your virtual network and click Forward.
Figure 16.32. Naming your virtual network
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Creating a virtual network
3.
Enter an IPv4 address space for your virtual network and click Forward.
Figure 16.33. Choosing an IPv4 address space
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Chapter 16. Managing guests with the Virtual Machine Manager (virt-manager)
4.
Define the DHCP range for your virtual network by specifying a Start and End range of IP
addresses. Click Forward to continue.
Figure 16.34. Selecting the DHCP range
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Creating a virtual network
5.
Select how the virtual network should connect to the physical network.
Figure 16.35. Connecting to physical network
If you select Forwarding to physical network, choose whether the Destination should be NAT
to any physical device or NAT to physical device eth0.
Click Forward to continue.
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6.
You are now ready to create the network. Check the configuration of your network and click
Finish.
Figure 16.36. Ready to create network
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Creating a virtual network
7.
The new virtual network is now available in the Virtual Network tab of the Host Details menu.
Figure 16.37. New virtual network is now available
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Part V. Tips and Tricks
Tips and Tricks to
Enhance Productivity
These chapters contain useful hints and tips to improve virtualization performance, scale and stability.
Chapter 17.
Tips and tricks
This chapter contain useful hints and tips to improve virtualization performance, scale and stability.
17.1. Automatically starting guests
This section covers how to make virtualized guests start automatically during the host system's boot
phase.
This example uses virsh to set a guest, TestServer, to automatically start when the host boots.
# virsh autostart TestServer
Domain TestServer marked as autostarted
The guest now automatically starts with the host.
To stop a guest automatically booting use the --disable parameter
# virsh autostart --disable TestServer
Domain TestServer unmarked as autostarted
The guest no longer automatically starts with the host.
17.2. Changing between the KVM and Xen hypervisors
This section covers changing between the KVM and Xen hypervisors.
Fedora only supports one active hypervisor at a time.
Migrating virtualized guests between hypervisors
Presently, there is no application for switching Xen-based guests to KVM or KVM-based
guests to Xen. Guests can only be used on the hypervisor type that they were created on.
17.2.1. Xen to KVM
The following procedure covers changing from the Xen hypervisor to the KVM hypervisor. This
procedure assumes the kernel-xen package is installed and enabled.
1.
Install the KVM package
Install the kvm package if you have not already done so.
# yum install kvm
2.
Verify which kernel is in use
The kernel-xen package may be installed. Use the uname command to determine which kernel is
running:
$ uname -r
2.6.23.14-107.fc8xen
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Chapter 17. Tips and tricks
The "2.6.23.14-107.fc8xen" kernel is running on the system. If the default kernel,
"2.6.23.14-107.fc8", is running you can skip the substep.
•
Changing the Xen kernel to the default kernel
The grub.conf file determines which kernel is booted. To change the default kernel edit the
/boot/grub/grub.conf file as shown below.
default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.23.14-107.fc8)
root (hd0,0)
kernel /vmlinuz-2.6.23.14-107.fc8 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.23.14-107.fc8.img
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
kernel /xen.gz-2.6.23.14-107.fc8
module /vmlinuz-2.6.23.14-107.fc8xen ro root=/dev/VolGroup00/LogVol00 rhgb
quiet
module /initrd-2.6.23.14-107.fc8xen.img
Notice the default=1 parameter. This is instructing the GRUB boot loader to boot the second
entry, the Xen kernel. Change the default to 0 (or the number for the default kernel):
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.23.14-107.fc8)
root (hd0,0)
kernel /vmlinuz-2.6.23.14-107.fc8 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.23.14-107.fc8.img
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
kernel /xen.gz-2.6.23.14-107.fc8
module /vmlinuz-2.6.23.14-107.fc8xen ro root=/dev/VolGroup00/LogVol00 rhgb
quiet
module /initrd-2.6.23.14-107.fc8xen.img
3.
Reboot to load the new kernel
Reboot the system. The computer will restart with the default kernel. The KVM module should be
automatically loaded with the kernel. Verify KVM is running:
$ lsmod | grep kvm
kvm_intel
kvm
85992
222368
1
2 ksm,kvm_intel
The kvm module and either the kvm_intel module or the kvm_amd module are present if
everything worked.
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KVM to Xen
17.2.2. KVM to Xen
The following procedure covers changing from the KVM hypervisor to the Xen hypervisor. This
procedure assumes the kvm package is installed and enabled.
1.
Install the Xen packages
Install the kernel-xen and xen package if you have not already done so.
# yum install kernel-xen xen
The kernel-xen package may be installed but disabled.
2.
Verify which kernel is in use
Use the uname command to determine which kernel is running.
$ uname -r
2.6.23.14-107.fc8
The "2.6.23.14-107.fc8" kernel is running on the system. This is the default kernel. If the
kernel has xen on the end (for example, 2.6.23.14-107.fc8xen) then the Xen kernel is
running and you can skip the substep.
•
Changing the default kernel to the Xen kernel
The grub.conf file determines which kernel is booted. To change the default kernel edit the
/boot/grub/grub.conf file as shown below.
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.23.14-107.fc8)
root (hd0,0)
kernel /vmlinuz-2.6.23.14-107.fc8 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.23.14-107.fc8.img
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
kernel /xen.gz-2.6.23.14-107.fc8
module /vmlinuz-2.6.23.14-107.fc8xen ro root=/dev/VolGroup00/LogVol00 rhgb
quiet
module /initrd-2.6.23.14-107.fc8xen.img
Notice the default=0 parameter. This is instructing the GRUB boot loader to boot the first
entry, the default kernel. Change the default to 1 (or the number for the Xen kernel):
default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.23.14-107.fc8)
root (hd0,0)
kernel /vmlinuz-2.6.23.14-107.fc8 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.23.14-107.fc82.6.23.14-107.fc8.img
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
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Chapter 17. Tips and tricks
kernel /xen.gz-2.6.23.14-107.fc8
module /vmlinuz-2.6.23.14-107.fc8xen ro root=/dev/VolGroup00/LogVol00 rhgb
quiet
module /initrd-2.6.23.14-107.fc8xen.img
3.
Reboot to load the new kernel
Reboot the system. The computer will restart with the Xen kernel. Verify with the uname
command:
$ uname -r
2.6.23.14-107.fc8xen
If the output has xen on the end the Xen kernel is running.
17.3. Using qemu-img
The qemu-img command line tool is used for formatting various file systems used by Xen and KVM.
qemu-img should be used for formatting virtualized guest images, additional storage devices and
network storage. qemu-img options and usages are listed below.
Formatting and creating new images or devices
Create the new disk image filename of size size and format format.
# qemu-img create [-6] [-e] [-b base_image] [-f format] filename [size]
If base_image is specified, then the image will record only the differences from base_image. No size
needs to be specified in this case. base_image will never be modified unless you use the "commit"
monitor command.
Convert an existing image to another format
The convert option is used for converting a recognized format to another image format.
Command format:
# qemu-img convert [-c] [-e] [-f format] filename [-O output_format] output_filename
convert the disk image filename to disk image output_filename using format output_format. it can be
optionally encrypted ("-e" option) or compressed ("-c" option).
only the format "qcow" supports encryption or compression. the compression is read-only. it means
that if a compressed sector is rewritten, then it is rewritten as uncompressed data.
The encryption uses the AES format with very secure 128 bit keys. use a long password (16
characters) to get maximum protection.
image conversion is also useful to get smaller image when using a format which can grow, such as
qcow or cow. The empty sectors are detected and suppressed from the destination image.
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Overcommitting with KVM
getting image information
the info parameter displays information about a disk image. the format for the info option is as
follows:
# qemu-img info [-f format] filename
give information about the disk image filename. use it in particular to know the size reserved on disk
which can be different from the displayed size. if vm snapshots are stored in the disk image, they are
displayed too.
Supported formats
The format of an image is usually guessed automatically. The following formats are supported:
raw
Raw disk image format (default). This format has the advantage of being simple and easily
exportable to all other emulators. If your file system supports holes (for example in ext2 or ext3
on Linux or NTFS on Windows), then only the written sectors will reserve space. Use qemu-img
info to know the real size used by the image or ls -ls on Unix/Linux.
qcow2
QEMU image format, the most versatile format. Use it to have smaller images (useful if your file
system does not supports holes, for example: on Windows), optional AES encryption, zlib based
compression and support of multiple VM snapshots.
qcow
Old QEMU image format. Only included for compatibility with older versions.
cow
User Mode Linux Copy On Write image format. The cow format is included only for compatibility
with previous versions. It does not work with Windows.
vmdk
VMware 3 and 4 compatible image format.
cloop
Linux Compressed Loop image, useful only to reuse directly compressed CD-ROM images
present for example in the Knoppix CD-ROMs.
17.4. Overcommitting with KVM
The KVM hypervisor supports overcommitting CPUs and overcommitting memory. Overcommitting is
allocating more virtualized CPUs or memory than there are physical resources on the system. With
CPU overcommit, under-utilized virtualized servers or desktops can run on fewer servers which saves
power and money.
Xen support
CPU overcommitting is not supported for the Xen hypervisor. Overcommitting CPUs with
the Xen hypervisor may cause system instability and crashes of the host and virtualized
guests.
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Chapter 17. Tips and tricks
Overcommitting memory
Most operating systems and applications do not use 100% of the available RAM all the time. This
behavior can be exploited with KVM to use more memory for virtualized guests than what is physically
available.
With KVM, virtual machines are Linux processes. Guests on the KVM hypervisor do not have blocks
of physical RAM assigned to them instead they function as processes. Each process is allocated
memory when it requests more memory. KVM uses this to allocate memory for guests when the guest
operating system requests more or less memory. The guest only uses slightly more physical memory
than the virtualized operating system appears to use.
When physical memory is nearly completely used or a process is inactive for some time, Linux moves
the process's memory to swap. Swap is usually a partition on a hard disk drive or solid state drive
which Linux uses to extend virtual memory. Swap is significantly slower than RAM.
As KVM virtual machines are Linux processes, memory used by virtualized guests can be put into
swap if the guest is idle or not in heavy use. Memory can be committed over the total size of the
swap and physical RAM. This can cause issues if virtualized guests use their total RAM. Without
sufficient swap space for the virtual machine processes to be swapped to the pdflush process
starts. pdflush kills processes to free memory so the system does not crash. pdflush may destroy
virtualized guests or other system processes which may cause file system errors and may leave
virtualized guests unbootable.
Warning
If sufficient swap is not available guest operating systems will be forcibly shut down. This
may leave guests inoperable. Avoid this by never overcommitting more memory than
there is swap available.
The swap partition is used for swapping underused memory to the hard drive to speed up memory
performance. The default size of the swap partition is calculated from amount of RAM and overcommit
ratio. It is recommended to make your swap partition larger if you intend to overcommit memory with
KVM. A recommended overcommit ratio is 50% (0.5). The formula used is:
(0.5 * RAM) + (overcommit ratio * RAM) = Recommended swap size
The Red Hat Knowledgebase has an article on safely and efficiently determining the size of the swap
1
partition — refer to Knowledgebase .
It is possible to run with an overcommit ratio of ten times the number of virtualized guests over the
amount of physical RAM in the system. This only works with certain application loads (for example
desktop virtualization with under 100% usage). Setting overcommit ratios is not a hard formula, you
must test and customize the ratio for your environment.
Overcommitting virtualized CPUs
The KVM hypervisor supports overcommitting virtualized CPUs. Virtualized CPUs can be
overcommitted as far as load limits of virtualized guests allow. Use caution when overcommitting
VCPUs as loads near 100% may cause dropped requests or unusable response times.
1
http://kbase.redhat.com/faq/docs/DOC-15252
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Modifying /etc/grub.conf
Virtualized CPUs are overcommitted best when each virtualized guest only has a single VCPU. The
Linux scheduler is very efficient with this type of load. KVM should safely support guests with loads
under 100% at a ratio of 5 VCPUs Overcommitting single VCPU virtualized guests is not an issue.
You cannot overcommit symmetric multiprocessing guests on more than the physical number of
processing cores. For example a guest with four VCPUs should not be run on a host with a dual
core processor. Overcommitting symmetric multiprocessing guests in over the physical number of
processing cores will cause significant performance degradation.
Assigning guests VCPUs up to the number of physical cores is appropriate and works as expected.
For example, running virtualized guests with four VCPUs on a quad core host. Guests with less than
100% loads should function effectively in this setup.
Always test first
Do not overcommit memory or CPUs in a production environment without extensive
testing. Applications which use 100% of memory or processing resources may become
unstable in overcommitted environments. Test before deploying.
17.5. Modifying /etc/grub.conf
This section describes how to safely and correctly change your /etc/grub.conf file to use the
virtualization kernel. You must use the xen kernel to use the Xen hypervisor. Copy your existing
xen kernel entry make sure you copy all of the important lines or your system will panic upon boot
(initrd will have a length of '0'). If you require xen hypervisor specific values you must append them
to the xen line of your grub entry.
The output below is an example of a grub.conf entry from a system running the kernel-xen package.
The grub.conf on your system may vary. The important part in the example below is the section
from the title line to the next new line.
#boot=/dev/sda
default=0
timeout=15
#splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
kernel /xen.gz-2.6.23.14-107.fc8 com1=115200,8n1
module /vmlinuz-2.6.23.14-107.fc8xen ro root=/dev/VolGroup00/LogVol00
module /initrd-2.6.23.14-107.fc8xen.img
An important point regarding editing grub.conf...
Your grub.conf could look very different if it has been manually edited before or copied
from an example.
To set the amount of memory assigned to your host system at boot time to 256MB you need to append
dom0_mem=256M to the xen line in your grub.conf. A modified version of the grub configuration file
in the previous example:
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Chapter 17. Tips and tricks
#boot=/dev/sda
default=0
timeout=15
#splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console
title Fedora (2.6.23.14-107.fc8xen)
root (hd0,0)
kernel /xen.gz-2.6.23.14-107.fc8 com1=115200,8n1 dom0_mem=256MB
module /vmlinuz-2.6.23.14-107.fc8xen ro
root=/dev/VolGroup00/LogVol00
module /initrd-2.6.23.14-107.fc8xen.img
17.6. Verifying virtualization extensions
Use this section to determine whether your system has the hardware virtualization extensions.
Virtualization extensions (Intel VT or AMD-V) are required for full virtualization.
Can I use virtualization without the virtualization extensions?
If hardware virtualization extensions are not present you can use Xen para-virtualization
with the fedora kernel-xen package.
Run the following command to verify the CPU virtualization extensions are available:
$ grep -E 'svm|vmx' /proc/cpuinfo
The following output contains a vmx entry indicating an Intel processor with the Intel VT extensions:
flags
: fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush
dts acpi mmx fxsr sse sse2 ss ht tm syscall lm constant_tsc pni monitor ds_cpl
vmx est tm2 cx16 xtpr lahf_lm
The following output contains an svm entry indicating an AMD processor with the AMD-V extensions:
flags
: fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush
mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni cx16
lahf_lm cmp_legacy svm cr8legacy ts fid vid ttp tm stc
The "flags:" content may appear multiple times for each hyperthread, core or CPU on in the system.
The virtualization extensions may be disabled in the BIOS. If the extensions do not appear or full
virtualization does not work refer to Procedure 19.1, “Enabling virtualization extensions in BIOS”.
17.7. Identifying guest type and implementation
The script below can identify if the environment an application or script is running in is a paravirtualized, a fully virtualized guest or on the hypervisor.
218
Generating a new unique MAC address
#!/bin/bash
declare -i IS_HVM=0
declare -i IS_PARA=0
check_hvm()
{
IS_X86HVM="$(strings /proc/acpi/dsdt | grep int-xen)"
if [ x"${IS_X86HVM}" != x ]; then
echo "Guest type is full-virt x86hvm"
IS_HVM=1
fi
}
check_para()
{
if $(grep -q control_d /proc/xen/capabilities); then
echo "Host is dom0"
IS_PARA=1
else
echo "Guest is para-virt domU"
IS_PARA=1
fi
}
if [ -f /proc/acpi/dsdt ]; then
check_hvm
fi
if [ ${IS_HVM} -eq 0 ]; then
if [ -f /proc/xen/capabilities ] ; then
check_para
fi
fi
if [ ${IS_HVM} -eq 0 -a ${IS_PARA} -eq 0 ]; then
echo "Baremetal platform"
fi
Examining hosts
For examining hosts, use the virsh capabilites command.
17.8. Generating a new unique MAC address
In some case you will need to generate a new and unique MAC address for a guest. There is no
command line tool available to generate a new MAC address at the time of writing. The script
provided below can generate a new MAC address for your guests. Save the script to your guest as
macgen.py. Now from that directory you can run the script using ./macgen.py . and it will generate
a new MAC address. A sample output would look like the following:
$ ./macgen.py
00:16:3e:20:b0:11
#!/usr/bin/python
# macgen.py script to generate a MAC address for virtualized guests on Xen
#
import random
#
def randomMAC():
mac = [ 0x00, 0x16, 0x3e,
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Chapter 17. Tips and tricks
random.randint(0x00, 0x7f),
random.randint(0x00, 0xff),
random.randint(0x00, 0xff) ]
return ':'.join(map(lambda x: "%02x" % x, mac))
#
print randomMAC()
Another method to generate a new MAC for your guest
You can also use the built-in modules of python-virtinst to generate a new MAC address and
UUID for use in a guest configuration file:
# echo 'import virtinst.util ; print\
virtinst.util.uuidToString(virtinst.util.randomUUID())' | python
# echo 'import virtinst.util ; print virtinst.util.randomMAC()' | python
The script above can also be implemented as a script file as seen below.
#!/usr/bin/env python
# -*- mode: python; -*print ""
print "New UUID:"
import virtinst.util ; print virtinst.util.uuidToString(virtinst.util.randomUUID())
print "New MAC:"
import virtinst.util ; print virtinst.util.randomMAC()
print ""
17.9. Very Secure ftpd
vsftpd can provide access to installation trees for para-virtualized guests or other data. If you have
not installed vsftpd during the server installation you can grab the RPM package from your Server
directory of your installation media and install it using the rpm -ivh vsftpd*.rpm (note that the
RPM package must be in your current directory).
1. To configure vsftpd, edit /etc/passwd using vipw and change the ftp user's home directory to
the directory where you are going to keep the installation trees for your para-virtualized guests. An
example entry for the FTP user would look like the following:
ftp:x:14:50:FTP User:/xen/pub:/sbin/nologin
2. to have vsftpd start automatically during system boot use the chkconfig utility to enable the
automatic start up of vsftpd.
3. verify that vsftpd is not enabled using the chkconfig --list vsftpd:
$ chkconfig --list vsftpd
vsftpd
0:off
1:off
2:off
3:off
4:off
5:off
6:off
4. run the chkconfig --levels 345 vsftpd on to start vsftpd automatically for run levels 3, 4
and 5.
220
Configuring LUN Persistence
5. use the chkconfig --list vsftpd command to verify vsftdp has been enabled to start during
system boot:
$ chkconfig --list vsftpd
vsftpd
0:off
1:off
2:off
3:on
4:on
5:on
6:off
6. use the service vsftpd start vsftpd to start the vsftpd service:
$service vsftpd start vsftpd
Starting vsftpd for vsftpd:
[
OK
]
17.10. Configuring LUN Persistence
This section covers how to implement LUN persistence in guests and on the host machine with and
without multipath.
Implementing LUN persistence without multipath
If your system is not using multipath, you can use udev to implement LUN persistence. Before
implementing LUN persistence in your system, ensure that you acquire the proper UUIDs. Once you
acquire these, you can configure LUN persistence by editing the scsi_id file that resides in the /etc
directory. Once you have this file open in a text editor, you must comment out this line:
# options=-b
Then replace it with this parameter:
# options=-g
This tells udev to monitor all system SCSI devices for returning UUIDs. To determine the system
UUIDs, use the scsi_id command:
# scsi_id -g -s /block/sdc
*3600a0b80001327510000015427b625e*
The long string of characters in the output is the UUID. The UUID does not change when you add
a new device to your system. Acquire the UUID for each the device in order to create rules for the
devices. To create new device rules, edit the 20-names.rules file in the /etc/udev/rules.d
directory. The device naming rules follow this format:
# KERNEL="sd*",
BUS="scsi",
PROGRAM="sbin/scsi_id", RESULT="UUID", NAME="devicename"
Replace your existing UUID and devicename with the above UUID retrieved entry. The rule should
resemble the following:
KERNEL="sd*", BUS="scsi",
NAME="mydevicename"
PROGRAM="sbin/scsi_id", RESULT="3600a0b80001327510000015427b625e",
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Chapter 17. Tips and tricks
This enables all devices that match the /dev/sd* pattern to inspect the given UUID. When it finds a
matching device, it creates a device node called /dev/devicename. For this example, the device
node is /dev/mydevice . Finally, append the /etc/rc.local file with this line:
/sbin/start_udev
Implementing LUN persistence with multipath
To implement LUN persistence in a multipath environment, you must define the alias names
for the multipath devices. For this example, you must define four device aliases by editing the
multipath.conf file that resides in the /etc/ directory:
multipath
}
multipath
}
multipath
}
multipath
{
wwid
alias
3600a0b80001327510000015427b625e
oramp1
wwid
alias
3600a0b80001327510000015427b6
oramp2
wwid
alias
3600a0b80001327510000015427b625e
oramp3
wwid
alias
3600a0b80001327510000015427b625e
oramp4
{
{
{
}
This defines 4 LUNs: /dev/mpath/oramp1, /dev/mpath/oramp2, /dev/mpath/oramp3, and
dev/mpath/oramp4. The devices will reside in the /dev/mpath directory. These LUN names are
persistent over reboots as it creates the alias names on the wwid of the LUNs.
17.11. Disable SMART disk monitoring for guests
SMART disk monitoring can be disabled as we are running on virtual disks and the physical storage is
managed by the host.
/sbin/service smartd stop
/sbin/chkconfig --del smartd
17.12. Cloning guest configuration files
You can copy an existing configuration file to create an all new guest. You must modify the name
parameter of the guests' configuration file. The new, unique name then appears in the hypervisor and
is viewable by the management utilities. You must generate an all new UUID as well by using the
uuidgen command. Then for the vif entries you must define a unique MAC address for each guest
(if you are copying a guest configuration from an existing guest, you can create a script to handle it).
For the xen bridge information, if you move an existing guest configuration file to a new host, you must
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Duplicating an existing guest and its configuration file
update the xenbr entry to match your local networking configuration. For the Device entries, you must
modify the entries in the 'disk=' section to point to the correct guest image.
You must also modify these system configuration settings on your guest. You must modify the
HOSTNAME entry of the /etc/sysconfig/network file to match the new guest's hostname.
You must modify the HWADDR address of the /etc/sysconfig/network-scripts/ifcfg-eth0
file to match the output from ifconfig eth0 file and if you use static IP addresses, you must modify
the IPADDR entry.
17.13. Duplicating an existing guest and its configuration
file
This section outlines copying an existing configuration file to create a new guest. There are key
parameters in your guest's configuration file you must be aware of, and modify, to successfully
duplicate a guest.
name
The name of your guest as it is known to the hypervisor and displayed in the management utilities.
This entry should be unique on your system.
uuid
A unique handle for the guest, a new UUID can be regenerated using the uuidgen command. A
sample UUID output:
$ uuidgen
a984a14f-4191-4d14-868e-329906b211e5
vif
• The MAC address must define a unique MAC address for each guest. This is automatically
done if the standard tools are used. If you are copying a guest configuration from an existing
guest you can use the script Section 17.8, “Generating a new unique MAC address”.
• If you are moving or duplicating an existing guest configuration file to a new host you have to
make sure you adjust the xenbr entry to correspond with your local networking configuration
(you can obtain the bridge information using the command brctl show command).
• Device entries, make sure you adjust the entries in the disk= section to point to the correct
guest image.
Now, adjust the system configuration settings on your guest:
/etc/sysconfig/network
Modify the HOSTNAME entry to the guest's new hostname.
/etc/sysconfig/network-scripts/ifcfg-eth0
• Modify the HWADDR address to the output from ifconfig eth0
• Modify the IPADDR entry if a static IP address is used.
223
224
Chapter 18.
Creating custom libvirt scripts
This section provides some information which may be useful to programmers and system
administrators intending to write custom scripts to make their lives easier by using libvirt.
Chapter 17, Tips and tricks is recommended reading for programmers thinking of writing new
applications which use libvirt.
18.1. Using XML configuration files with virsh
virsh can handle XML configuration files. You may want to use this to your advantage for scripting
large deployments with special options. You can add devices defined in an XML file to a running paravirtualized guest. For example, to add a ISO file as hdc to a running guest create an XML file:
# cat satelliteiso.xml
<disk type="file" device="disk">
<driver name="file"/>
<source file="/var/lib/libvirt/images/rhn-satellite-5.0.1-11-redhat-linux-as-i386-4-embeddedoracle.iso"/>
<target dev="hdc"/>
<readonly/>
</disk>
Run virsh attach-device to attach the ISO as hdc to a guest called "satellite" :
# virsh attach-device satellite satelliteiso.xml
225
226
Part VI. Troubleshooting
Introduction to Troubleshooting
and Problem Solving
The following chapters provide information to assist you in troubleshooting issues you may encounter
using virtualization.
Important note on virtualization issues
Your particular problem may not appear in this book due to ongoing development which
creates and fixes bugs. For the most up to date list of known bugs, issues and bug
fixes read the Fedora Release Notes for your version and hardware architecture. The
Release Notes can be found in the documentation section of the Fedora website, http://
docs.fedoraproject.org.
Chapter 19.
Troubleshooting
This chapter covers common problems and solutions with Fedora virtualization.
19.1. Loop device errors
If file based guest images are used you may have to increase the number of configured loop
devices. The default configuration allows up to 8 active loop devices. If more than 8 file based
guests or loop devices are needed the number of loop devices configured can be adjusted in /etc/
modprobe.conf. Edit /etc/modprobe.conf and add the following line to it:
options loop max_loop=64
This example uses 64 but you can specify another number to set the maximum loop value. You may
also have to implement loop device backed guests on your system. To employ loop device backed
guests for a para-virtualized guest, use the phy: block device or tap:aio commands. To employ
loop device backed guests for a full virtualized system, use the phy: device or file: file
commands.
19.2. Enabling Intel VT and AMD-V virtualization hardware
extensions in BIOS
This section describes how to identify hardware virtualization extensions and enable them in your
BIOS if they are disabled.
The Intel VT extensions can be disabled in the BIOS. Certain laptop vendors have disabled the Intel
VT extensions by default in their CPUs.
The virtualization extensions can not be disabled in the BIOS for AMD-V ( capable processors
installed in a Rev 2 socket.
The virtualization extensions are sometimes disabled in BIOS, usually by laptop manufacturers.
Refer to Section 19.2, “Enabling Intel VT and AMD-V virtualization hardware extensions in BIOS” for
instructions on enabling disabled virtualization extensions.
Verify the virtualization extensions are enabled in BIOS. The BIOS settings for Intel® VT or AMDV are usually in the Chipset or Processor menus. The menu names may vary from this guide, the
virtualization extension settings may be found in Security Settings or other non standard menu
names.
Procedure 19.1. Enabling virtualization extensions in BIOS
1. Reboot the computer and open the system's BIOS menu. This can usually be done by pressing
delete or Alt + F4.
2.
Select Restore Defaults, and then select Save & Exit.
3.
Power off the machine and disconnect the power supply.
4.
Power on the machine and open the BIOS Setup Utility. Open the Processor section
and enable Intel®Virtualization Technology or AMD-V. The values may also be called
Virtualization Extensions on some machines. Select Save & Exit.
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Chapter 19. Troubleshooting
5.
Power off the machine and disconnect the power supply.
6.
Run cat /proc/cpuinfo | grep vmx svm. If the command outputs, the virtualization
extensions are now enabled. If there is no output your system may not have the virtualization
extensions or the correct BIOS setting enabled.
230
Appendix A. Additional resources
To learn more about virtualization and Linux, refer to the following resources.
A.1. Online resources
• http://www.cl.cam.ac.uk/research/srg/netos/xen/ The project website of the Xen™ para-virtualization
machine manager from which the Fedora kernel-xen package is derived. The site maintains
the upstream xen project binaries and source code and also contains information, architecture
overviews, documentation, and related links regarding xen and its associated technologies.
• The Xen Community website
http://www.xen.org/
• http://www.libvirt.org/ is the official website for the libvirt virtualization API.
• http://virt-manager.et.redhat.com/ is the project website for the Virtual Machine Manager (virtmanager), the graphical application for managing virtual machines.
• Open Virtualization Center
http://www.openvirtualization.com
1
• Fedora Documentation
http://docs.fedoraproject.org
• Virtualization technologies overview
http://virt.kernelnewbies.org
2
• Red Hat Emerging Technologies group
3
http://et.redhat.com
A.2. Installed documentation
• /usr/share/doc/xen-<version-number>/ is the directory which contains information about
the Xen para-virtualization hypervisor and associated management tools, including various example
configurations, hardware-specific information, and the current Xen upstream user documentation.
• man virsh and /usr/share/doc/libvirt-<version-number> — Contains sub commands
and options for the virsh virtual machine management utility as well as comprehensive information
about the libvirt virtualization library API.
• /usr/share/doc/gnome-applet-vm-<version-number> — Documentation for the GNOME
graphical panel applet that monitors and manages locally-running virtual machines.
• /usr/share/doc/libvirt-python-<version-number> — Provides details on the Python
bindings for the libvirt library. The libvirt-python package allows python developers to
create programs that interface with the libvirt virtualization management library.
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Appendix A. Additional resources
• /usr/share/doc/python-virtinst-<version-number> — Provides documentation on
the virt-install command that helps in starting installations of Fedora and Linux related
distributions inside of virtual machines.
• /usr/share/doc/virt-manager-<version-number> — Provides documentation on the
Virtual Machine Manager, which provides a graphical tool for administering virtual machines.
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Appendix B. Revision History
Revision
12.1.3
Mon Oct 12 2009
Christopher Curran ccurran@redhat.com
Split from Red Hat Enterprise Linux 5.4 Virtualization Guide version 5.4-61.
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Appendix C. Colophon
This manual was written in the DocBook XML v4.3 format.
This book is based on the work of Jan Mark Holzer and Chris Curran.
Other writing credits go to:
• Don Dutile contributed technical editing for the para-virtualized drivers section.
• Barry Donahue contributed technical editing for the para-virtualized drivers section.
• Rick Ring contributed technical editing for the Virtual Machine Manager Section.
• Michael Kearey contributed technical editing for the sections on using XML configuration files with
virsh and virtualized floppy drives.
• Marco Grigull contributed technical editing for the software compatibility and performance section.
• Eugene Teo contributed technical editing for the Managing Guests with virsh section.
Publican, the publishing tool which produced this book, was written by Jeffrey Fearn.
The Red Hat Localization Team consists of the following people:
East Asian Languages
• Simplified Chinese
• Leah Wei Liu
• Traditional Chinese
• Chester Cheng
• Terry Chuang
• Japanese
• Junko Ito
• Korean
• Eun-ju Kim
Latin Languages
• French
• Sam Friedmann
• German
• Hedda Peters
• Italian
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Appendix C. Colophon
• Francesco Valente
• Brazilian Portuguese
• Glaucia de Freitas
• Leticia de Lima
• Spanish
• Angela Garcia
• Gladys Guerrero
• Russian
• Yuliya Poyarkova
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Glossary
This glossary is intended to define the terms used in this Installation Guide.
Bare-metal
The term bare-metal refers to the underlying physical architecture of a
computer. Running an operating system on bare-metal is another way
of referring to running an unmodified version of the operating system
on the physical hardware. Examples of operating systems running on
bare metal are dom0 or a normally installed operating system.
dom0
Also known as the Host or host operating system.
dom0 refers to the host instance of Linux running the Hypervisor
which facilitates virtualization of guest operating systems. Dom0 runs
on and manages the physical hardware and resource allocation for
itself and the guest operating systems.
Domains
domU and Domains are both domains. Domains run on the
Hypervisor. The term domains has a similar meaning to Virtual
machines and the two are technically interchangeable. A domain is a
Virtual Machine.
domU
domU refers to the guest operating system which run on the host
system (Domains).
Full virtualization
Xen and KVM can use full virtualization. Full virtualization uses
hardware features of the processor to provide total abstraction
of the underlying physical system (Bare-metal) and create a new
virtual system in which the guest operating systems can run. No
modifications are needed in the guest operating system. The guest
operating system and any applications on the guest are not aware
of the virtualized environment and run normally. Para-virtualization
requires a modified version of the Linux operating system.
Fully virtualized
See Full virtualization.
Guest system
Also known as guests, virtual machines or domU.
Hardware Virtual Machine
See Full virtualization
Host
The host operating system, also known as dom0.
The host operating system environment runs the virtualization
software for Fully virtualized and Para-virtualized guest systems.
Hypervisor
The hypervisor is the software layer that abstracts the hardware from
the operating system permitting multiple operating systems to run on
the same hardware. The hypervisor runs on a host operating system
allowing other virtualized operating systems to run on the host's
hardware.
I/O
Short for input/output (pronounced "eye-oh"). The term I/O describes
any program, operation or device that transfers data to or from a
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Glossary
computer and to or from a peripheral device. Every transfer is an
output from one device and an input into another. Devices such as
keyboards and mouses are input-only devices while devices such as
printers are output-only. A writable CD-ROM is both an input and an
output device.
Kernel-based Virtual
Machine
KVM (Kernel-based Virtual Machine) is a Full virtualization solution for
Linux on AMD64 and Intel 64 hardware. VM is a Linux kernel module
built for the standard Linux kernel. KVM can run multiple, unmodified
virtualized guest Windows and Linux operating systems. KVM is a
hypervisor which uses the libvirt virtualization tools (virt-manager and
virsh).
KVM is a set of Linux kernel modules which manage devices,
memory and management APIs for the Hypervisor module itself.
Virtualized guests are run as Linux processes and threads which are
controlled by these modules.
LUN
A Logical Unit Number (LUN) is a number assigned to a logical unit (a
SCSI protocol entity).
MAC Addresses
The Media Access Control Address is the hardware address for a
Network Interface Controller. In the context of virtualization MAC
addresses must be generated for virtual network interfaces with each
MAC on your local domain being unique.
Migration
Migration is name for the process of moving a virtualized guest from
one host to another. Migration can be conducted offline (where the
guest is suspended and then moved) or live (where a guest is moved
without suspending). Xen fully virtualized guests, Xen para-virtualized
guest and KVM fully virtualized guests can all be migrated.
Migration is a key feature of virtualization as software is completely
separated from hardware. Migration is useful for:
• Load balancing - guests can be moved to hosts with lower usage
when a host becomes overloaded.
• Hardware failover - when hardware devices on the host start to fail,
guests can be safely relocated so the host can be powered down
and repaired.
• Energy saving - guests can be redistributed to other hosts and host
systems powered off to save energy and cut costs in low usage
periods.
• Geographic migration - guests can be moved to another location for
lower latency or in serious circumstances.
Shared, networked storage is used for storing guest images. Without
shared storage migration is not possible.
An offline migration suspends the guest then moves an image of the
guests memory to the destination host. The guest is resumed on the
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destination host and the memory the guest used on the source host is
freed.
The time an offline migration takes depends network bandwidth and
latency. A guest with 2GB of memory should take several seconds on
a 1 Gbit Ethernet link.
A live migration keeps the guest running on the source host and
begins moving the memory without stopping the guest. All modified
memory pages are tracked and sent to the destination after the image
is sent. The memory is updated with the changed pages. The process
continues until it reaches some heuristic; either it successfully
copied all the pages over, or the source is changing too fast and
the destination host cannot make progress. If the heuristic is met
the guest is briefly paused on the source host and the registers and
buffers are sent. The registers are loaded on the new host and the
guest is then resumed on the destination host. If the guest cannot be
merged (which happens when guests are under extreme loads) the
guest is paused and then an offline migration is started instead.
The time an offline migration takes depends network bandwidth and
latency as well as activity on the guest. If the guest is using significant
I/O or CPU the migration will take much longer.
Para-virtualization
Para-virtualization uses a special kernel, sometimes referred to as the
Xen kernel or the kernel-xen package. Para-virtualized guest kernels
are run concurrently on the host while using the host's libraries and
devices. A para-virtualized installation can have complete access to
all devices on the system which can be limited with security settings
(SELinux and file controls). Para-virtualization is faster than full
virtualization. Para-virtualization can effectively be used for load
balancing, provisioning, security and consolidation advantages.
As of Fedora 9 a special kernel will no longer be needed. Once this
patch is accepted into the main Linux tree all Linux kernels after that
version will have para-virtualization enabled or available.
Para-virtualized
See Para-virtualization,
Para-virtualized drivers
Para-virtualized drivers are device drivers that operate on fully
virtualized Linux guests. These drivers greatly increase performance
of network and block device I/O for fully virtualized guests.
Security Enhanced Linux
Short for Security Enhanced Linux, SELinux uses Linux Security
Modules (LSM) in the Linux kernel to provide a range of minimum
privilege required security policies.
Universally Unique Identifier
A Universally Unique Identifier (UUID) is a standardized numbering
method for devices, systems and certain software objects in
distributed computing environments. Types of UUIDs in virtualization
include: ext2 and ext3 file system identifiers, RAID device
identifiers, iSCSI and LUN device identifiers, MAC addresses and
virtual machine identifiers.
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Glossary
Virtual machines
A virtual machine is a software implementation of a physical
machine or programming language (for example the Java Runtime
Environment or LISP). Virtual machines in the context of virtualization
are operating systems running on virtualized hardware.
Virtualization
Virtualization is a board computing term for running software, usually
operating systems, concurrently and isolated from other programs
on one system. Most existing implementations of virtualization use a
hypervisor, a software layer on top of an operating system, to abstract
hardware. The hypervisor allows multiple operating systems to run
on the same physical system by giving the guest operating system
virtualized hardware. There are various methods for virtualizing
operating systems:
• Hardware-assisted virtualization is the technique used for full
virtualization with Xen and KVM (definition: Full virtualization)
• Para-virtualization is a technique used by Xen to run Linux guests
(definition: Para-virtualization)
• Software virtualization or emulation. Software virtualization uses
binary translation and other emulation techniques to run unmodified
operating systems. Software virtualization is significantly slower
than hardware-assisted virtualization or para-virtualization.
Virtualized CPU
A system has a number of virtual CPUs (VCPUs) relative to the
number of physical processor cores. The number of virtual CPUs is
finite and represents the total number of virtual CPUs that can be
assigned to guest virtual machines.
Xen
Fedora supports the Xen hypervisor and the KVM hypervisor (refer
to Kernel-based Virtual Machine). Both hypervisors have different
architectures and development approaches. The Xen hypervisor runs
underneath a Linux operating system which acts as a host managing
system resources and virtualization APIs. The host is sometimes
referred to as as dom0 or Domain0.
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