Installation guide | Red Hat Enterprise Linux 5 Global File System 2

Red Hat Enterprise Linux 5
Global File System 2
Red Hat Global File System 2
Edition 7
Red Hat Enterprise Linux 5 Global File System 2
Red Hat Global File System 2
Edition 7
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Abstract
This bo o k pro vides info rmatio n abo ut co nfiguring and maintaining Red Hat GFS2 (Red Hat
Glo bal File System 2) fo r Red Hat Enterprise Linux 5.
T able of Cont ent s
T able of Contents
.Int
. .roduct
. . . . . .ion
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. . . . . . . . . .
⁠1. Aud ienc e
4
⁠2 . Related Do c umentatio n
4
⁠3 . Feed b ac k
5
⁠4 . Do c ument Co nventio ns
5
⁠4 .1. Typ o g rap hic Co nventio ns
5
⁠4 .2. Pull-q uo te Co nventio ns
⁠4 .3. No tes and Warning s
6
7
. .hapt
⁠C
. . . .er
. .1. .. G
. .FS2
...O
. .verview
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. . . . . . . . . .
⁠1.1. Befo re Setting Up G FS2
9
⁠1.2. Differenc es b etween G FS and G FS2
10
⁠1.2.1. G FS2 Co mmand Names
10
⁠1.2.2. Ad d itio nal Differenc es Between G FS and G FS2
11
. . . . .ext
Cont
. . .- Dependent
. . . . . . . . . . .Pat
. . .h. Names
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 1. . . . . . . . . .
. . . . .ko
gfs2
. . . Module
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 1. . . . . . . . . .
. . . . . . . . .Q. uot
Enabling
...a
. .Enforcement
. . . . . . . . . . . .in
. .G. FS2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 1. . . . . . . . . .
. . . .a. Journaling
Dat
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 1. . . . . . . . . .
. . . . . . . Journals
Adding
. . . . . . . . Dynamically
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 1. . . . . . . . . .
. . ime_quant
at
. . . . . . . . . .um
. . .paramet
. . . . . . .er
. . removed
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 2. . . . . . . . . .
. .he
T
. . dat
. . . a=
. . . opt
. . . ion
. . . .of
. .t.he
. . mount
. . . . . . .command
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 2. . . . . . . . . .
. .he
T
. . gfs2
. . . . _t
. . ool
. . . .command
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 2. . . . . . . . . .
. .he
T
. . gfs2
. . . . _edit
. . . . . command
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 2. . . . . . . . . .
⁠1.2.3. G FS2 Perfo rmanc e Imp ro vements
12
. .hapt
⁠C
. . . .er
. .2. .. G
. .et. t. ing
. . . .St
. .art
. . ed
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 4. . . . . . . . . .
⁠2 .1. Prereq uis ite Tas ks
14
⁠2 .2. Initial Setup Tas ks
14
. .hapt
⁠C
. . . .er
. .3.
. .Managing
. . . . . . . . .G
. .FS2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 6. . . . . . . . . .
⁠3 .1. Making a File Sys tem
16
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 6. . . . . . . . . .
Usage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 8. . . . . . . . . .
Examples
.Complet
. . . . . . .e. O
. .pt
. .ions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 8. . . . . . . . . .
⁠3 .2. Mo unting a File Sys tem
19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 0. . . . . . . . . .
Usage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 0. . . . . . . . . .
Example
.Complet
. . . . . . .e. Usage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 0. . . . . . . . . .
⁠3 .3. Unmo unting a File Sys tem
22
.Usage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 2. . . . . . . . . .
⁠3 .4. Sp ec ial Co ns id eratio ns when Mo unting G FS2 File Sys tems
22
⁠3 .5. G FS2 Q uo ta Manag ement
23
1
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
⁠3 .5. G FS2 Q uo ta Manag ement
⁠3 .5.1. Setting Q uo tas
23
23
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 3. . . . . . . . . .
Usage
.Examples
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 4. . . . . . . . . .
⁠3 .5.2. Dis p laying Q uo ta Limits and Us ag e
24
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 4. . . . . . . . . .
Usage
. . . . . . . . . .O. ut
Command
. . put
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 5. . . . . . . . . .
. . . . . . . . .s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 5. . . . . . . . . .
Comment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 6. . . . . . . . . .
Examples
⁠3 .5.3. Sync hro niz ing Q uo tas
26
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 6. . . . . . . . . .
Usage
.Examples
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 6. . . . . . . . . .
⁠3 .5.4. Enab ling /Dis ab ling Q uo ta Enfo rc ement
27
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 7. . . . . . . . . .
Usage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 7. . . . . . . . . .
Examples
⁠3 .5.5. Enab ling Q uo ta Ac c o unting
27
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 7. . . . . . . . . .
Usage
.Example
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 8. . . . . . . . . .
⁠3 .6 . G ro wing a File Sys tem
28
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 8. . . . . . . . . .
Usage
. . . . . . . . .s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 8. . . . . . . . . .
Comment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 9. . . . . . . . . .
Examples
. . . . . . . .e. Usage
Complet
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 9. . . . . . . . . .
⁠3 .7. Ad d ing Jo urnals to a File Sys tem
30
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Usage
...........
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Examples
...........
. . . . . . . .e. Usage
Complet
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
...........
⁠3 .8 . Data Jo urnaling
⁠3 .9 . Co nfig uring atime Up d ates
31
32
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Usage
...........
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Example
...........
⁠3 .10 . Sus p end ing Ac tivity o n a File Sys tem
33
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Usage
...........
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Examples
...........
⁠3 .11. Rep airing a File Sys tem
33
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Usage
...........
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Example
...........
2
T able of Cont ent s
.Example
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
...........
⁠3 .12. Bind Mo unts and Co ntext-Dep end ent Path Names
35
⁠3 .13. Bind Mo unts and File Sys tem Mo unt O rd er
⁠3 .14. The G FS2 Withd raw Func tio n
37
38
. . . . . . . ing
Convert
. . . .a. File
. . . .Syst
. . . .em
. . .from
. . . .G
. .FS
. . t. o
. .G. FS2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. 1. . . . . . . . . .
. . . . . . . . .Hist
Revision
. . . ory
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 3. . . . . . . . . .
⁠I.ndex
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 5. . . . . . . . . .
3
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Introduction
This book provides information about configuring and maintaining Red Hat GFS2 (Red Hat Global
File System 2). Red Hat GFS2 can be run in Red Hat Enterprise Linux 5.3 and later. For the Red Hat
Enterprise Linux 5.5 release and later, Red Hat does not support the use of GFS2 as a single-node
file system. For information about Red Hat Cluster Suite see Red Hat Cluster Suite Overview and
Configuring and Managing a Red Hat Cluster.
HTML and PD F versions of all the official Red Hat Enterprise Linux manuals and release notes are
available online at https://access.redhat.com/site/documentation/en-US/.
1. Audience
This book is intended primarily for Linux system administrators who are familiar with the following
activities:
Linux system administration procedures, including kernel configuration
Installation and configuration of shared storage networks, such as Fibre Channel SANs
2. Relat ed Document at ion
For more information about using Red Hat Enterprise Linux, refer to the following resources:
Red Hat Enterprise Linux Installation Guide — Provides information regarding installation of Red Hat
Enterprise Linux.
Red Hat Enterprise Linux Deployment Guide — Provides information regarding the deployment,
configuration and administration of Red Hat Enterprise Linux 5.
For more information about Red Hat Cluster Suite, refer to the following resources:
Red Hat Cluster Suite Overview — Provides a high level overview of the Red Hat Cluster Suite.
Configuring and Managing a Red Hat Cluster — Provides information about installing, configuring
and managing Red Hat Cluster components.
Logical Volume Manager Administration — Provides a description of the Logical Volume Manager
(LVM), including information on running LVM in a clustered environment.
Global File System: Configuration and Administration — Provides information about installing,
configuring, and maintaining Red Hat GFS (Red Hat Global File System).
Using Device-Mapper Multipath — Provides information about using the D evice-Mapper Multipath
feature of Red Hat Enterprise Linux.
Using GNBD with Global File System — Provides an overview on using Global Network Block
D evice (GNBD ) with Red Hat GFS.
Linux Virtual Server Administration — Provides information on configuring high-performance
systems and services with the Linux Virtual Server (LVS).
Red Hat Cluster Suite Release Notes — Provides information about the current release of Red Hat
Cluster Suite.
4
Int roduct ion
Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML, PD F, and
RPM versions on the Red Hat Enterprise Linux D ocumentation CD and online at
https://access.redhat.com/site/documentation/en-US/.
3. Feedback
If you spot a typo, 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/). File the bug
against the product R ed H at En t erp rise Lin u x 5 and against the component D o cu men t at io n clu st er.
Be sure to mention the manual's identifier:
rh-gfs2(EN)-5 (2014-6-30T15:15)
By mentioning this manual's identifier, we know exactly which version of the guide you have.
If you have a suggestion for improving the documentation, try to be as specific as possible. If you
have found an error, please include the section number and some of the surrounding text so we can
find it easily.
4 . Document Convent ions
This manual uses several conventions to highlight certain words and phrases and draw attention to
specific pieces of information.
4 .1. T ypographic Convent ions
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 keys 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 key, all presented in mono-spaced bold and
all distinguishable thanks to context.
Key combinations can be distinguished from an individual key by the plus sign that connects each
part of a key combination. For example:
Press Enter to execute the command.
Press Ctrl+Alt+F2 to switch to a virtual terminal.
The first example highlights a particular key to press. The second example highlights a key
combination: a set of three keys 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:
5
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
File-related classes include filesystem for file systems, file for files, and dir for
directories. Each class has its own associated set of permissions.
Pro p o rt io n al B o ld
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 submenu titles. For
example:
Choose Syst em → Pref eren ces → Mo u se from the main menu bar to launch
Mo u se Pref eren ces. In the Buttons tab, select 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 g ed it file, choose Ap p licat io n s →
Accesso ries → C h aract er Map from the main menu bar. Next, choose Search →
Fin d … from the C h aract er 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. D ouble-click 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 Ed it → Past e from the g ed it 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.
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.
4 .2. Pull-quot e Convent ions
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:
6
Int roduct ion
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:
​static int kvm_vm_ioctl_deassign_device(struct kvm *kvm,
​
struct kvm_assigned_pci_dev *assigned_dev)
​
{
​
int r = 0;
​
struct kvm_assigned_dev_kernel *match;
​
mutex_lock(&kvm->lock);
​
​
match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
assigned_dev->assigned_dev_id);
if (!match) {
printk(KERN_INFO "%s: device hasn't been assigned before, "
"so cannot be deassigned\n", __func__);
r = -EINVAL;
goto out;
}
​
kvm_deassign_device(kvm, match);
​
kvm_free_assigned_device(kvm, match);
​
​
​
​
​
​
​out:
​
mutex_unlock(&kvm->lock);
return r;
​
​}
4 .3. Not es 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” will not cause data loss but may cause irritation and frustration.
Warning
Warnings should not be ignored. Ignoring warnings will most likely cause data loss.
7
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Chapter 1. GFS2 Overview
The Red Hat GFS2 file system is a native file system that interfaces directly with the Linux kernel file
system interface (VFS layer). When implemented as a cluster file system, GFS2 employs distributed
metadata and multiple journals. Red Hat supports the use of GFS2 file systems only as implemented
in Red Hat Cluster Suite.
Note
Although a GFS2 file system can be implemented in a standalone system or as part of a
cluster configuration, for the Red Hat Enterprise Linux 5.5 release and later Red Hat does not
support the use of GFS2 as a single-node file system. Red Hat does support a number of highperformance single node file systems which are optimized for single node and thus have
generally lower overhead than a cluster file system. Red Hat recommends using these file
systems in preference to GFS2 in cases where only a single node needs to mount the file
system.
Red Hat will continue to support single-node GFS2 file systems for existing customers.
Note
Red Hat does not support using GFS2 for cluster file system deployments greater than 16
nodes.
GFS2 is based on a 64-bit architecture, which can theoretically accommodate an 8 EB file system.
However, the current supported maximum size of a GFS2 file system for 64-bit hardware is 100 TB.
The current supported maximum size of a GFS2 file system for 32-bit hardware for Red Hat Enterprise
Linux Release 5.3 and later is 16 TB. If your system requires larger GFS2 file systems, contact your
Red Hat service representative.
When determining the size of your file system, you should consider your recovery needs. Running the
fsck.gfs2 command on a very large file system can take a long time and consume a large amount
of memory. Additionally, in the event of a disk or disk-subsytem failure, recovery time is limited by the
speed of your backup media. For information on the amount of memory the fsck.gfs2 command
requires, see Section 3.11, “ Repairing a File System” .
When configured in a Red Hat Cluster Suite, Red Hat GFS2 nodes can be configured and managed
with Red Hat Cluster Suite configuration and management tools. Red Hat GFS2 then provides data
sharing among GFS2 nodes in a Red Hat cluster, with a single, consistent view of the file system
name space across the GFS2 nodes. This allows processes on different nodes to share GFS2 files in
the same way that processes on the same node can share files on a local file system, with no
discernible difference. For information about Red Hat Cluster Suite refer to Configuring and Managing a
Red Hat Cluster.
While a GFS2 file system may be used outside of LVM, Red Hats supports only GFS2 file systems that
are created on a CLVM logical volume. CLVM is a cluster-wide implementation of LVM, enabled by the
CLVM daemon clvmd, which manages LVM logical volumes in a Red Hat Cluster Suite cluster. The
daemon makes it possible to use LVM2 to manage logical volumes across a cluster, allowing all
nodes in the cluster to share the logical volumes. For information on the LVM volume manager, see
Logical Volume Manager Administration
8
⁠Chapt er 1 . G FS2 O verview
The gfs2.ko kernel module implements the GFS2 file system and is loaded on GFS2 cluster nodes.
Note
When you configure a GFS2 file system as a cluster file system, you must ensure that all nodes
in the cluster have access to the shared storage. Asymmetric cluster configurations in which
some nodes have access to the shared storage and others do not are not supported. This
does not require that all nodes actually mount the GFS2 file system itself.
This chapter provides some basic, abbreviated information as background to help you understand
GFS2. It contains the following sections:
Section 1.1, “ Before Setting Up GFS2”
Section 1.2, “ D ifferences between GFS and GFS2”
1.1. Before Set t ing Up GFS2
Before you install and set up GFS2, note the following key characteristics of your GFS2 file systems:
G FS2 n o d es
D etermine which nodes in the Red Hat Cluster Suite will mount the GFS2 file systems.
N u mb er o f f ile syst ems
D etermine how many GFS2 file systems to create initially. (More file systems can be added
later.)
File syst em n ame
D etermine a unique name for each file system. The name must be unique for all lock_dlm
file systems over the cluster, and for all file systems (lock_dlm and lock_nolock) on
each local node. Each file system name is required in the form of a parameter variable. For
example, this book uses file system names mydata1 and mydata2 in some example
procedures.
Jo u rn als
D etermine the number of journals for your GFS2 file systems. One journal is required for
each node that mounts a GFS2 file system. GFS2 allows you to add journals dynamically
at a later point as additional servers mount a file system. For information on adding
journals to a GFS2 file system, see Section 3.7, “ Adding Journals to a File System” .
G N B D server n o d es
If you are using GNBD , determine how many GNBD server nodes are needed. Note the
hostname and IP address of each GNBD server node for setting up GNBD clients later. For
information on using GNBD with GFS2, see the Using GNBD with Global File System
document.
St o rag e d evices an d p art it io n s
D etermine the storage devices and partitions to be used for creating logical volumes (via
CLVM) in the file systems.
9
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Note
You may see performance problems with GFS2 when many create and delete operations are
issued from more than one node in the same directory at the same time. If this causes
performance problems in your system, you should localize file creation and deletions by a
node to directories specific to that node as much as possible.
1.2. Differences bet ween GFS and GFS2
This section lists the improvements and changes that GFS2 offers over GFS.
Migrating from GFS to GFS2 requires that you convert your GFS file systems to GFS2 with the
gfs2_convert utility. For information on the gfs2_convert utility, see Appendix A, Converting a File
System from GFS to GFS2.
1.2.1. GFS2 Command Names
In general, the functionality of GFS2 is identical to GFS. The names of the file system commands,
however, specify GFS2 instead of GFS. Table 1.1, “ GFS and GFS2 Commands” shows the
equivalent GFS and GFS2 commands.
T ab le 1.1. G FS an d G FS2 C o mman d s
G FS C o mman d
G FS2 C o mman d
D escrip t io n
mount
mount
umount
umount
Mount a file system. The system can determine whether the
file system is a GFS or GFS2 file system type. For
information on the GFS2 mount options see the
gfs2_mount(8) man page.
Unmount a file system.
fsck
fsck
gfs_fsck
fsck.gfs2
gfs_grow
gfs2_grow
Grow a mounted file system.
gfs_jadd
gfs2_jadd
Add a journal to a mounted file system.
gfs_mkfs
mkfs.gfs2
mkfs -t gfs
mkfs -t gfs2
gfs_quota
gfs2_quota
Manage quotas on a mounted file system.
gfs_tool
gfs2_tool
Configure, tune, or gather information about a file system.
gfs_edit
gfs2_edit
gfs_tool
setflag
jdata/inherit
_jdata
chattr +j
(preferred)
D isplay, print, or edit file system internal structures. The
gfs2_edit command can be used for GFS file systems
as well as GFS2 file system.
Enable journaling on a file or directory.
setfacl/getfa
cl
setfacl/getfa
cl
10
Check and repair an unmounted file system.
Create a file system on a storage device.
Set or get file access control list for a file or directory.
Cont ext - Dependent Pat h Names
G FS C o mman d
G FS2 C o mman d
D escrip t io n
setfattr/getf
attr
setfattr/getf
attr
set or get the extended attributes of a file.
For a full listing of the supported options for the GFS2 file system commands, see the man pages for
those commands.
1.2.2. Addit ional Differences Bet ween GFS and GFS2
This section summarizes the additional differences in GFS and GFS2 administration that are not
described in Section 1.2.1, “ GFS2 Command Names” .
Context-Dependent Path Names
GFS2 file systems do not provide support for context-dependent path names, which allow you to
create symbolic links that point to variable destination files or directories. For this functionality in
GFS2, you can use the bind option of the mount command. For information on managing
pathnames in GFS2, see Section 3.12, “ Bind Mounts and Context-D ependent Path Names” .
gfs2.ko Module
The kernel module that implements the GFS file system is gfs.ko. The kernel module that implements
the GFS2 file system is gfs2.ko.
Enabling Quota Enforcement in GFS2
In GFS2 file systems, quota enforcement is disabled by default and must be explicitly enabled. To
enable and disable quotas for GFS2 file systems, you use the quota=on|off|account option for
the mount command. For information on enabling and disabling quota enforcement, see
Section 3.5.4, “ Enabling/D isabling Quota Enforcement” .
Data Journaling
GFS2 file systems support the use of the chattr command to set and clear the j flag on a file or
directory. Setting the +j flag on a file enables data journaling on that file. Setting the +j flag on a
directory means " inherit jdata" , which indicates that all files and directories subsequently created in
that directory are journaled. Using the chattr command is the preferred way to enable and disable
data journaling on a file.
Adding Journals Dynamically
In GFS file systems, journals are embedded metadata that exists outside of the file system, making it
necessary to extend the size of the logical volume that contains the file system before adding
journals. In GFS2 file systems, journals are plain (though hidden) files. This means that for GFS2 file
systems, journals can be dynamically added as additional servers mount a file system, as long as
space remains on the file system for the additional journals. For information on adding journals to a
GFS2 file system, see Section 3.7, “ Adding Journals to a File System” .
11
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
atime_quantum parameter removed
The GFS2 file system does not support the atime_quantum tunable parameter, which can be used
by the GFS file system to specify how often atime updates occur. In its place GFS2 supports the
relatime and noatime mount options. The relatime mount option is recommended to achieve
similar behavior to setting the atime_quantum parameter in GFS.
The data= option of the mount command
When mounting GFS2 file systems, you can specify the data=ordered or data=writeback option
of the mount. When data=ordered is set, the user data modified by a transaction is flushed to the
disk before the transaction is committed to disk. This should prevent the user from seeing
uninitialized blocks in a file after a crash. When data=writeback is set, the user data is written to
the disk at any time after it is dirtied. This does not provide the same consistency guarantee as
ordered mode, but it should be slightly faster for some workloads. The default is ordered mode.
The gfs2_tool command
The gfs2_tool command supports a different set of options for GFS2 than the gfs_tool command
supports for GFS:
The gfs2_tool command supports a journals parameter that prints out information about the
currently configured journals, including how many journals the file system contains.
The gfs2_tool command does not support the counters flag, which the gfs_tool command
uses to display GFS statistics.
The gfs2_tool command does not support the inherit_jdata flag. To flag a directory as
" inherit jdata" , you can set the jdata flag on the directory or you can use the chattr command
to set the +j flag on the directory. Using the chattr command is the preferred way to enable and
disable data journaling on a file.
The gfs2_edit command
The gfs2_edit command supports a different set of options for GFS2 than the gfs_edit command
supports for GFS. For information on the specific options each version of the command supports,
see the gfs2_edit and gfs_edit man pages.
1.2.3. GFS2 Performance Improvement s
There are many features of GFS2 file systems that do not result in a difference in the user interface
from GFS file systems but which improve file system performance.
A GFS2 file system provides improved file system performance in the following ways:
Better performance for heavy usage in a single directory
Faster synchronous I/O operations
Faster cached reads (no locking overhead)
12
at ime_quant um paramet er removed
Faster direct I/O with preallocated files (provided I/O size is reasonably large, such as 4M blocks)
Faster I/O operations in general
Faster Execution of the df command, because of faster statfs calls
Improved atime mode to reduce the number of write I/O operations generated by atime when
compared with GFS
GFS2 file systems provide broader and more mainstream support in the following ways:
GFS2 is part of the upstream kernel (integrated into 2.6.19).
GFS2 supports the following features.
extended file attributes (xattr)
the lsattr() and chattr() attribute settings via standard ioctl() calls
nanosecond timestamps
A GFS2 file system provides the following improvements to the internal efficiency of the file system:
GFS2 uses less kernel memory.
GFS2 requires no metadata generation numbers.
Allocating GFS2 metadata does not require reads. Copies of metadata blocks in multiple journals
are managed by revoking blocks from the journal before lock release.
GFS2 includes a much simpler log manager that knows nothing about unlinked inodes or quota
changes.
The gfs2_grow and gfs2_jadd commands use locking to prevent multiple instances running at
the same time.
The ACL code has been simplified for calls like creat() and mkdir().
Unlinked inodes, quota changes, and statfs changes are recovered without remounting the
journal.
13
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Chapter 2. Getting Started
This chapter describes procedures for initial setup of GFS2 and contains the following sections:
Section 2.1, “ Prerequisite Tasks”
Section 2.2, “ Initial Setup Tasks”
2.1. Prerequisit e T asks
You should complete the following tasks before setting up Red Hat GFS2:
Make sure that you have noted the key characteristics of the GFS2 nodes (refer to Section 1.1,
“ Before Setting Up GFS2” ).
Make sure that the clocks on the GFS2 nodes are synchronized. It is recommended that you use
the Network Time Protocol (NTP) software provided with your Red Hat Enterprise Linux
distribution.
Note
The system clocks in GFS2 nodes must be within a few minutes of each other to prevent
unnecessary inode time-stamp updating. Unnecessary inode time-stamp updating severely
impacts cluster performance.
In order to use GFS2 in a clustered environment, you must configure your system to use the
Clustered Logical Volume Manager (CLVM), a set of clustering extensions to the LVM Logical
Volume Manager. In order to use CLVM, the Red Hat Cluster Suite software, including the clvmd
daemon, must be running. For information on using CLVM, see Logical Volume Manager
Administration. For information on installing and administering Red Hat Cluster Suite, see Cluster
Administration.
2.2. Init ial Set up T asks
Initial GFS2 setup consists of the following tasks:
1. Setting up logical volumes.
2. Making a GFS2 files system.
3. Mounting file systems.
Follow these steps to set up GFS2 initially.
1. Using LVM, create a logical volume for each Red Hat GFS2 file system.
Note
You can use init.d scripts included with Red Hat Cluster Suite to automate
activating and deactivating logical volumes. For more information about init.d
scripts, refer to Configuring and Managing a Red Hat Cluster.
14
⁠Chapt er 2 . G et t ing St art ed
2. Create GFS2 file systems on logical volumes created in Step 1. Choose a unique name for
each file system. For more information about creating a GFS2 file system, refer to Section 3.1,
“ Making a File System” .
You can use either of the following formats to create a clustered GFS2 file system:
mkfs.gfs2 -p lock_dlm -t ClusterName:FSName -j NumberJournals BlockDevice
mkfs -t gfs2 -p lock_dlm -t LockTableName -j NumberJournals BlockDevice
You can use either of the following formats to create a local GFS2 file system:
mkfs.gfs2 -p lock_nolock -j NumberJournals BlockDevice
mkfs -t gfs2 -p lock_nolock -j NumberJournals BlockDevice
For more information on creating a GFS2 file system, see Section 3.1, “ Making a File System” .
3. At each node, mount the GFS2 file systems. For more information about mounting a GFS2 file
system, see Section 3.2, “ Mounting a File System” .
Command usage:
mount BlockDevice MountPoint
mount -o acl BlockDevice MountPoint
The -o acl mount option allows manipulating file ACLs. If a file system is mounted without
the -o acl mount option, users are allowed to view ACLs (with getfacl), but are not
allowed to set them (with setfacl).
Note
You can use init.d scripts included with Red Hat Cluster Suite to automate mounting
and unmounting GFS2 file systems. For more information about init.d scripts, refer
to Configuring and Managing a Red Hat Cluster.
15
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Chapter 3. Managing GFS2
This chapter describes the tasks and commands for managing GFS2 and consists of the following
sections:
Section 3.1, “ Making a File System”
Section 3.2, “ Mounting a File System”
Section 3.3, “ Unmounting a File System”
Section 3.5, “ GFS2 Quota Management”
Section 3.6, “ Growing a File System”
Section 3.7, “ Adding Journals to a File System”
Section 3.8, “ D ata Journaling”
Section 3.9, “ Configuring atime Updates”
Section 3.10, “ Suspending Activity on a File System”
Section 3.11, “ Repairing a File System”
Section 3.12, “ Bind Mounts and Context-D ependent Path Names”
Section 3.13, “ Bind Mounts and File System Mount Order”
Section 3.14, “ The GFS2 Withdraw Function”
3.1. Making a File Syst em
You create a GFS2 file system with the mkfs.gfs2 command. You can also use the mkfs command
with the -t gfs2 option specified. A file system is created on an activated LVM volume. The following
information is required to run the mkfs.gfs2 command:
Lock protocol/module name (the lock protocol for a cluster is lock_dlm)
Cluster name (when running as part of a cluster configuration)
Number of journals (one journal required for each node that may be mounting the file system)
When creating a GFS2 file system, you can use the mkfs.gfs2 command directly, or you can use
the mkfs command with the -t parameter specifying a file system of type gfs2, followed by the gfs2
file system options.
Note
Once you have created a GFS2 file system with the mkfs.gfs2 command, you cannot
decrease the size of the file system. You can, however, increase the size of an existing file
system with the gfs2_grow command, as described in Section 3.6, “ Growing a File System” .
Usage
16
⁠Chapt er 3. Managing G FS2
When creating a clustered GFS2 file system, you can use either of the following formats:
mkfs.gfs2 -p LockProtoName -t LockTableName -j NumberJournals BlockDevice
mkfs -t gfs2 -p LockProtoName -t LockTableName -j NumberJournals BlockDevice
When creating a local GFS2 file system, you can use either of the following formats:
Note
For the Red Hat Enterprise Linux 5.5 release and later Red Hat does not support the use of
GFS2 as a single-node file system. Red Hat will continue to support single-node GFS2 file
systems for existing customers.
mkfs.gfs2 -p LockProtoName -j NumberJournals BlockDevice
mkfs -t gfs2 -p LockProtoName -j NumberJournals BlockDevice
Warning
Make sure that you are very familiar with using the LockProtoName and LockTableName
parameters. Improper use of the LockProtoName and LockTableName parameters may
cause file system or lock space corruption.
LockProtoName
Specifies the name of the locking protocol to use. The lock protocol for a cluster is
lock_dlm.
LockTableName
This parameter is specified for GFS2 file system in a cluster configuration. It has two parts
separated by a colon (no spaces) as follows: ClusterName:FSName
ClusterName, the name of the Red Hat cluster for which the GFS2 file system is being
created.
FSName, the file system name, can be 1 to 16 characters long. The name must be unique
for all lock_dlm file systems over the cluster, and for all file systems (lock_dlm and
lock_nolock) on each local node.
Number
Specifies the number of journals to be created by the mkfs.gfs2 command. One journal is
required for each node that mounts the file system. For GFS2 file systems, more journals
can be added later without growing the file system, as described in Section 3.7, “ Adding
Journals to a File System” .
BlockDevice
Specifies a logical or physical volume.
17
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Examples
In these examples, lock_dlm is the locking protocol that the file system uses, since this is a
clustered file system. The cluster name is alpha, and the file system name is mydata1. The file
system contains eight journals and is created on /dev/vg01/lvol0.
mkfs.gfs2 -p lock_dlm -t alpha:mydata1 -j 8 /dev/vg01/lvol0
mkfs -t gfs2 -p lock_dlm -t alpha:mydata1 -j 8 /dev/vg01/lvol0
In these examples, a second lock_dlm file system is made, which can be used in cluster alpha. The
file system name is mydata2. The file system contains eight journals and is created on
/dev/vg01/lvol1.
mkfs.gfs2 -p lock_dlm -t alpha:mydata2 -j 8 /dev/vg01/lvol1
mkfs -t gfs2 -p lock_dlm -t alpha:mydata2 -j 8 /dev/vg01/lvol1
Complete Options
Table 3.1, “ Command Options: mkfs.gfs2” describes the mkfs.gfs2 command options (flags and
parameters).
T ab le 3.1. C o mman d O p t io n s: mkfs.gfs2
Flag
Paramet er
D escrip t io n
-c
Megabytes
-D
Sets the initial size of each journal's quota change file
to Megabytes .
Enables debugging output.
-h
Help. D isplays available options.
-J
MegaBytes
-j
Number
-O
-p
LockProtoName
Specifies the size of the journal in megabytes. D efault
journal size is 128 megabytes. The minimum size is 8
megabytes. Larger journals improve performance,
although they use more memory than smaller journals.
Specifies the number of journals to be created by the
mkfs.gfs2 command. One journal is required for
each node that mounts the file system. If this option is
not specified, one journal will be created. For GFS2
file systems, you can add additional journals at a later
time without growing the file system.
Prevents the mkfs.gfs2 command from asking for
confirmation before writing the file system.
Specifies the name of the locking protocol to use.
Recognized locking protocols include:
lock_dlm — The standard locking module, required
for a clustered file system.
lock_nolock — Used when GFS2 is acting as a
local file system (one node only).
18
Examples
Flag
Paramet er
D escrip t io n
Quiet. D o not display anything.
-q
-r
MegaBytes
Specifies the size of the resource groups in
megabytes. The minimum resource group size is 32
MB. The maximum resource group size is 2048 MB. A
large resource group size may increase performance
on very large file systems. If this is not specified,
mkfs.gfs2 chooses the resource group size based on
the size of the file system: average size file systems will
have 256 MB resource groups, and bigger file
systems will have bigger RGs for better performance.
-t
LockTableName
A unique identifier that specifies the lock table field
when you use the lock_dlm protocol; the
lock_nolock protocol does not use this parameter.
This parameter has two parts separated by a colon
(no spaces) as follows: ClusterName:FSName .
ClusterName is the name of the Red Hat cluster for
which the GFS2 file system is being created; only
members of this cluster are permitted to use this file
system. The cluster name is set in the
/etc/cluster/cluster.conf file via the C lu st er
C o n f ig u rat io n T o o l and displayed at the C lu st er
St at u s T o o l in the Red Hat Cluster Suite cluster
management GUI.
FSName , the file system name, can be 1 to 16
characters in length, and the name must be unique
among all file systems in the cluster.
-u
MegaBytes
-V
Specifies the initial size of each journal's unlinked tag
file.
D isplays command version information.
3.2. Mount ing a File Syst em
Before you can mount a GFS2 file system, the file system must exist (refer to Section 3.1, “ Making a
File System” ), the volume where the file system exists must be activated, and the supporting
clustering and locking systems must be started (refer to Configuring and Managing a Red Hat Cluster).
After those requirements have been met, you can mount the GFS2 file system as you would any Linux
file system.
To manipulate file ACLs, you must mount the file system with the -o acl mount option. If a file system
is mounted without the -o acl mount option, users are allowed to view ACLs (with getfacl), but are
not allowed to set them (with setfacl).
Usage
Mo u n t in g Wit h o u t AC L Man ip u lat io n
19
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
mount BlockDevice MountPoint
Mo u n t in g Wit h AC L Man ip u lat io n
mount -o acl BlockDevice MountPoint
-o acl
GFS2-specific option to allow manipulating file ACLs.
BlockDevice
Specifies the block device where the GFS2 file system resides.
MountPoint
Specifies the directory where the GFS2 file system should be mounted.
Example
In this example, the GFS2 file system on /dev/vg01/lvol0 is mounted on the /mygfs2 directory.
mount /dev/vg01/lvol0 /mygfs2
Complete Usage
mount BlockDevice MountPoint -o option
The -o option argument consists of GFS2-specific options (refer to Table 3.2, “ GFS2-Specific
Mount Options” ) or acceptable standard Linux mount -o options, or a combination of both. Multiple
option parameters are separated by a comma and no spaces.
Note
The mount command is a Linux system command. In addition to using GFS2-specific options
described in this section, you can use other, standard, mount command options (for example,
-r). For information about other Linux mount command options, see the Linux mount man
page.
Table 3.2, “ GFS2-Specific Mount Options” describes the available GFS2-specific -o option values
that can be passed to GFS2 at mount time.
Note
This table includes descriptions of options that are used with local file systems only For the
Red Hat Enterprise Linux 5.5 release and later Red Hat does not support the use of GFS2 as a
single-node file system. Red Hat will continue to support single-node GFS2 file systems for
existing customers.
20
Usage
T ab le 3.2. G FS2- Sp ecif ic Mo u n t O p t io n s
O p t io n
acl
data=[ordered|writeback]
ignore_local_fs
Caution: This option should not be used
when GFS2 file systems are shared.
localflocks
Caution: This option should not be
used when GFS2 file systems are shared.
D escrip t io n
Allows manipulating file ACLs. If a file system is
mounted without the acl mount option, users are
allowed to view ACLs (with getfacl ), but are not
allowed to set them (with setfacl ).
When data=ordered is set, the user data modified by
a transaction is flushed to the disk before the
transaction is committed to disk. This should prevent
the user from seeing uninitialized blocks in a file after
a crash. When data=writeback mode is set, the
user data is written to the disk at any time after it is
dirtied; this does not provide the same consistency
guarantee as ordered mode, but it should be slightly
faster for some workloads. The default value is
ordered mode.
Forces GFS2 to treat the file system as a multihost file
system. By default, using lock_nolock automatically
turns on the localflocks flags.
Tells GFS2 to let the VFS (virtual file system) layer do
all flock and fcntl. The localflocks flag is
automatically turned on by lock_nolock .
Note that the localflocks mount option affects only
advisory fcntl() /POSIX locks and flock locks that
are issued by applications. The internal locking that
ensures coherency of data across the cluster by
means of GFS2's glock abstraction is separate from
and not affected by the localflocks setting.
If you are unsure whether an application uses
fcntl() /POSIX locks and thus requires that you
mount your file system with the localflocks , you
can use the strace utility to print out the system calls
that are made during a test run of the application.
Look for fcntl calls that have F_GETLK , F_SETLK , or
F_SETLKW as the cmd argument.
Note that GFS2 does not currently support either
leases or mandatory locking.
lockproto=LockModuleName
locktable=LockTableName
Allows the user to specify which locking protocol to
use with the file system. If LockModuleName is not
specified, the locking protocol name is read from the
file system superblock.
Allows the user to specify which locking table to use
with the file system.
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
O p t io n
D escrip t io n
quota=[off/account/on]
Turns quotas on or off for a file system. Setting the
quotas to be in the account state causes the per
UID /GID usage statistics to be correctly maintained by
the file system; limit and warn values are ignored. The
default value is off .
errors=panic|withdraw
When errors=panic is specified, file system errors
will cause a kernel panic. The default behavior, which
is the same as specifying errors=withdraw , is for
the system to withdraw from the file system and make it
inaccessible until the next reboot; in some cases the
system may remain running. For information on the
GFS2 withdraw function, see Section 3.14, “ The GFS2
Withdraw Function” .
3.3. Unmount ing a File Syst em
The GFS2 file system can be unmounted the same way as any Linux file system — by using the
umount command.
Note
The umount command is a Linux system command. Information about this command can be
found in the Linux umount command man pages.
Usage
umount MountPoint
MountPoint
Specifies the directory where the GFS2 file system is currently mounted.
3.4 . Special Considerat ions when Mount ing GFS2 File Syst ems
GFS2 file systems that have been mounted manually rather than automatically through an entry in
the fstab file will not be known to the system when file systems are unmounted at system shutdown.
As a result, the GFS2 script will not unmount the GFS2 file system. After the GFS2 shutdown script is
run, the standard shutdown process kills off all remaining user processes, including the cluster
infrastructure, and tries to unmount the file system. This unmount will fail without the cluster
infrastructure and the system will hang.
To prevent the system from hanging when the GFS2 file systems are unmounted, you should do one
of the following:
Always use an entry in the fstab file to mount the GFS2 file system.
If a GFS2 file system has been mounted manually with the mount command, be sure to unmount
the file system manually with the umount command before rebooting or shutting down the system.
22
Usage
If your file system hangs while it is being unmounted during system shutdown under these
circumstances, perform a hardware reboot. It is unlikely that any data will be lost since the file system
is synced earlier in the shutdown process.
3.5. GFS2 Quot a Management
File-system quotas are used to limit the amount of file system space a user or group can use. A user
or group does not have a quota limit until one is set. GFS2 keeps track of the space used by each
user and group even when there are no limits in place. GFS2 updates quota information in a
transactional way so system crashes do not require quota usages to be reconstructed.
To prevent a performance slowdown, a GFS2 node synchronizes updates to the quota file only
periodically. The " fuzzy" quota accounting can allow users or groups to slightly exceed the set limit.
To minimize this, GFS2 dynamically reduces the synchronization period as a " hard" quota limit is
approached.
GFS2 uses its gfs2_quota command to manage quotas. Other Linux quota facilities cannot be
used with GFS2.
3.5.1. Set t ing Quot as
Two quota settings are available for each user ID (UID ) or group ID (GID ): a hard limit and a warn limit.
A hard limit is the amount of space that can be used. The file system will not let the user or group use
more than that amount of disk space. A hard limit value of zero means that no limit is enforced.
A warn limit is usually a value less than the hard limit. The file system will notify the user or group
when the warn limit is reached to warn them of the amount of space they are using. A warn limit value
of zero means that no limit is enforced.
Limits are set using the gfs2_quota command. The command only needs to be run on a single
node where GFS2 is mounted.
By default, quota enforcement is not set on GFS2 file systems. To enable quota accounting, use the
quota= of the mount command when mounting the GFS2 file system, as described in Section 3.5.4,
“ Enabling/D isabling Quota Enforcement” .
Usage
Set t in g Q u o t as, H ard Limit
gfs2_quota limit -u User -l Size -f MountPoint
gfs2_quota limit -g Group -l Size -f MountPoint
Set t in g Q u o t as, Warn Limit
gfs2_quota warn -u User -l Size -f MountPoint
gfs2_quota warn -g Group -l Size -f MountPoint
User
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
A user ID to limit or warn. It can be either a user name from the password file or the UID
number.
Group
A group ID to limit or warn. It can be either a group name from the group file or the GID
number.
Size
Specifies the new value to limit or warn. By default, the value is in units of megabytes. The
additional -k, -s and -b flags change the units to kilobytes, sectors, and file system
blocks, respectively.
MountPoint
Specifies the GFS2 file system to which the actions apply.
Examples
This example sets the hard limit for user Bert to 1024 megabytes (1 gigabyte) on file system /mygfs2.
gfs2_quota limit -u Bert -l 1024 -f /mygfs2
This example sets the warn limit for group ID 21 to 50 kilobytes on file system /mygfs2.
gfs2_quota warn -g 21 -l 50 -k -f /mygfs2
3.5.2. Displaying Quot a Limit s and Usage
Quota limits and current usage can be displayed for a specific user or group using the gfs2_quota
get command. The entire contents of the quota file can also be displayed using the gfs2_quota
list command, in which case all ID s with a non-zero hard limit, warn limit, or value are listed.
Usage
D isp layin g Q u o t a Limit s f o r a U ser
gfs2_quota get -u User -f MountPoint
D isp layin g Q u o t a Limit s f o r a G ro u p
gfs2_quota get -g Group -f MountPoint
D isp layin g En t ire Q u o t a File
gfs2_quota list -f MountPoint
User
A user ID to display information about a specific user. It can be either a user name from the
password file or the UID number.
24
Command O ut put
Group
A group ID to display information about a specific group. It can be either a group name
from the group file or the GID number.
MountPoint
Specifies the GFS2 file system to which the actions apply.
Command Output
GFS2 quota information from the gfs2_quota command is displayed as follows:
user User: limit:LimitSize warn:WarnSize value:Value
group Group: limit:LimitSize warn:WarnSize value:Value
The LimitSize, WarnSize, and Value numbers (values) are in units of megabytes by default.
Adding the -k, -s, or -b flags to the command line change the units to kilobytes, sectors, or file
system blocks, respectively.
User
A user name or ID to which the data is associated.
Group
A group name or ID to which the data is associated.
LimitSize
The hard limit set for the user or group. This value is zero if no limit has been set.
Value
The actual amount of disk space used by the user or group.
Comments
When displaying quota information, the gfs2_quota command does not resolve UID s and GID s
into names if the -n option is added to the command line.
Space allocated to GFS2's hidden files can be left out of displayed values for the root UID and GID
by adding the -d option to the command line. This is useful when trying to match the numbers from
gfs2_quota with the results of a du command.
Examples
This example displays quota information for all users and groups that have a limit set or are using
any disk space on file system /mygfs2.
gfs2_quota list -f /mygfs2
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
This example displays quota information in sectors for group users on file system /mygfs2.
gfs2_quota get -g users -f /mygfs2 -s
3.5.3. Synchroniz ing Quot as
GFS2 stores all quota information in its own internal file on disk. A GFS2 node does not update this
quota file for every file system write; rather, it updates the quota file once every 60 seconds. This is
necessary to avoid contention among nodes writing to the quota file, which would cause a slowdown
in performance.
As a user or group approaches their quota limit, GFS2 dynamically reduces the time between its
quota-file updates to prevent the limit from being exceeded. The normal time period between quota
synchronizations is a tunable parameter, quota_quantum, and can be changed using the
gfs2_tool command. By default, the time period is 60 seconds. Also, the quota_quantum
parameter must be set on each node and each time the file system is mounted. (Changes to the
quota_quantum parameter are not persistent across unmounts.)
You can use the gfs2_quota sync command to synchronize the quota information from a node to
the on-disk quota file between the automatic updates performed by GFS2.
Usage
Syn ch ro n iz in g Q u o t a In f o rmat io n
gfs2_quota sync -f MountPoint
MountPoint
Specifies the GFS2 file system to which the actions apply.
T u n in g t h e T ime B et ween Syn ch ro n iz at io n s
gfs2_tool settune MountPoint quota_quantum Seconds
MountPoint
Specifies the GFS2 file system to which the actions apply.
Seconds
Specifies the new time period between regular quota-file synchronizations by GFS2.
Smaller values may increase contention and slow down performance.
Examples
This example synchronizes the quota information from the node it is run on to file system /mygfs2.
gfs2_quota sync -f /mygfs2
This example changes the default time period between regular quota-file updates to one hour (3600
seconds) for file system /mygfs2 on a single node.
26
Usage
gfs2_tool settune /mygfs2 quota_quantum 3600
3.5.4 . Enabling/Disabling Quot a Enforcement
In GFS2 file systems, quota enforcement is disabled by default. To enable quota enforcement for a
file system, mount the file system with the quota=on option specified.
Usage
mount -o quota=on BlockDevice MountPoint
To mount a file system with quota enforcement disabled, mount the file system with the quota=off
option specified. This is the default setting.
mount -o quota=off BlockDevice MountPoint
-o quota={on|off}
Specifies that quota enforcement is enabled or disabled when the file system is mounted.
BlockDevice
Specifies the block device where the GFS2 file system resides.
MountPoint
Specifies the directory where the GFS2 file system should be mounted.
Examples
In this example, the GFS2 file system on /dev/vg01/lvol0 is mounted on the /mygfs2 directory
with quota enforcement enabled.
mount -o quota=on /dev/vg01/lvol0 /mygfs2
3.5.5. Enabling Quot a Account ing
It is possible to keep track of disk usage and maintain quota accounting for every user and group
without enforcing the limit and warn values. To do this, mount the file system with the
quota=account option specified.
Usage
mount -o quota=account BlockDevice MountPoint
-o quota=account
Specifies that user and group usage statistics are maintained by the file system, even
though the quota limits are not enforced.
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
BlockDevice
Specifies the block device where the GFS2 file system resides.
MountPoint
Specifies the directory where the GFS2 file system should be mounted.
Example
In this example, the GFS2 file system on /dev/vg01/lvol0 is mounted on the /mygfs2 directory
with quota accounting enabled.
mount -o quota=account /dev/vg01/lvol0 /mygfs2
3.6. Growing a File Syst em
The gfs2_grow command is used to expand a GFS2 file system after the device where the file system
resides has been expanded. Running a gfs2_grow command on an existing GFS2 file system fills
all spare space between the current end of the file system and the end of the device with a newly
initialized GFS2 file system extension. When the fill operation is completed, the resource index for the
file system is updated. All nodes in the cluster can then use the extra storage space that has been
added.
The gfs2_grow command must be run on a mounted file system, but only needs to be run on one
node in a cluster. All the other nodes sense that the expansion has occurred and automatically start
using the new space.
Note
Once you have created a GFS2 file system with the mkfs.gfs2 command, you cannot
decrease the size of the file system.
Usage
gfs2_grow MountPoint
MountPoint
Specifies the GFS2 file system to which the actions apply.
Comments
Before running the gfs2_grow command:
Back up important data on the file system.
28
Examples
D etermine the volume that is used by the file system to be expanded by running a df
MountPoint command.
Expand the underlying cluster volume with LVM. For information on administering LVM volumes,
see Logical Volume Manager Administration.
After running the gfs2_grow command, run a df command to check that the new space is now
available in the file system.
Examples
In this example, the file system on the /mygfs2fs directory is expanded.
[root@dash-01 ~]# gfs2_grow /mygfs2fs
FS: Mount Point: /mygfs2fs
FS: Device:
/dev/mapper/gfs2testvg-gfs2testlv
FS: Size:
524288 (0x80000)
FS: RG size:
65533 (0xfffd)
DEV: Size:
655360 (0xa0000)
The file system grew by 512MB.
gfs2_grow complete.
Complete Usage
gfs2_grow [Options] {MountPoint | Device} [MountPoint | Device]
MountPoint
Specifies the directory where the GFS2 file system is mounted.
Device
Specifies the device node of the file system.
Table 3.3, “ GFS2-specific Options Available While Expanding A File System” describes the GFS2specific options that can be used while expanding a GFS2 file system.
T ab le 3.3. G FS2- sp ecif ic O p t io n s Availab le Wh ile Exp an d in g A File Syst em
O p t io n
D escrip t io n
-h
Help. D isplays a short usage message.
-q
Quiet. Turns down the verbosity level.
-r MegaBytes
Specifies the size of the new resource group. The default size is
256MB.
Test. D o all calculations, but do not write any data to the disk and do
not expand the file system.
D isplays command version information.
-T
-V
3.7. Adding Journals t o a File Syst em
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
The gfs2_jadd command is used to add journals to a GFS2 file system. You can add journals to a
GFS2 file system dynamically at any point without expanding the underlying logical volume. The
gfs2_jadd command must be run on a mounted file system, but it needs to be run on only one node
in the cluster. All the other nodes sense that the expansion has occurred.
Note
If a GFS2 file system is full, the gfs2_jadd will fail, even if the logical volume containing the
file system has been extended and is larger than the file system. This is because in a GFS2 file
system, journals are plain files rather than embedded metadata, so simply extending the
underlying logical volume will not provide space for the journals.
Before adding journals to a GFS file system, you can use the journals option of the gfs2_tool to
find out how many journals the GFS2 file system currently contains. The following example displays
the number and size of the journals in the file system mounted at /mnt/gfs2.
[root@roth-01 ../cluster/gfs2]# gfs2_tool journals /mnt/gfs2
journal2 - 128MB
journal1 - 128MB
journal0 - 128MB
3 journal(s) found.
Usage
gfs2_jadd -j Number MountPoint
Number
Specifies the number of new journals to be added.
MountPoint
Specifies the directory where the GFS2 file system is mounted.
Examples
In this example, one journal is added to the file system on the /mygfs2 directory.
gfs2_jadd -j1 /mygfs2
In this example, two journals are added to the file system on the /mygfs2 directory.
gfs2_jadd -j2 /mygfs2
Complete Usage
gfs2_jadd [Options] {MountPoint | Device} [MountPoint | Device]
MountPoint
30
Usage
Specifies the directory where the GFS2 file system is mounted.
Device
Specifies the device node of the file system.
Table 3.4, “ GFS2-specific Options Available When Adding Journals” describes the GFS2-specific
options that can be used when adding journals to a GFS2 file system.
T ab le 3.4 . G FS2- sp ecif ic O p t io n s Availab le Wh en Ad d in g Jo u rn als
Flag
Paramet er
D escrip t io n
Help. D isplays short usage message.
-h
-J
MegaBytes
-j
Number
Specifies the size of the new journals in megabytes.
D efault journal size is 128 megabytes. The minimum
size is 32 megabytes. To add journals of different sizes
to the file system, the gfs2_jadd command must be
run for each size journal. The size specified is rounded
down so that it is a multiple of the journal-segment size
that was specified when the file system was created.
Specifies the number of new journals to be added by
the gfs2_jadd command. The default value is 1.
-q
Quiet. Turns down the verbosity level.
-V
D isplays command version information.
3.8. Dat a Journaling
Ordinarily, GFS2 writes only metadata to its journal. File contents are subsequently written to disk by
the kernel's periodic sync that flushes file system buffers. An fsync() call on a file causes the file's
data to be written to disk immediately. The call returns when the disk reports that all data is safely
written.
D ata journaling can result in a reduced fsync() time for very small files because the file data is
written to the journal in addition to the metadata. This advantage rapidly reduces as the file size
increases. Writing to medium and larger files will be much slower with data journaling turned on.
Applications that rely on fsync() to sync file data may see improved performance by using data
journaling. D ata journaling can be enabled automatically for any GFS2 files created in a flagged
directory (and all its subdirectories). Existing files with zero length can also have data journaling
turned on or off.
Enabling data journaling on a directory sets the directory to " inherit jdata" , which indicates that all
files and directories subsequently created in that directory are journaled. You can enable and
disable data journaling on a file with the chattr command.
The following commands enable data journaling on the /mnt/gfs2/gfs2_dir/newfile file and
then check whether the flag has been set properly.
[root@roth-01 ~]# chattr +j /mnt/gfs2/gfs2_dir/newfile
[root@roth-01 ~]# lsattr /mnt/gfs2/gfs2_dir
---------j--- /mnt/gfs2/gfs2_dir/newfile
The following commands disable data journaling on the /mnt/gfs2/gfs2_dir/newfile file and
then check whether the flag has been set properly.
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
[root@roth-01 ~]# chattr -j /mnt/gfs2/gfs2_dir/newfile
[root@roth-01 ~]# lsattr /mnt/gfs2/gfs2_dir
------------- /mnt/gfs2/gfs2_dir/newfile
You can also use the chattr command to set the j flag on a directory. When you set this flag for a
directory, all files and directories subsequently created in that directory are journaled. The following
set of commands sets the j flag on the gfs2_dir directory, then checks whether the flag has been
set properly. After this, the commands create a new file called newfile in the /mnt/gfs2/gfs2_dir
directory and then check whether the j flag has been set for the file. Since the j flag is set for the
directory, then newfile should also have journaling enabled.
[root@roth-01
[root@roth-01
---------j--[root@roth-01
[root@roth-01
---------j---
~]# chattr -j /mnt/gfs2/gfs2_dir
~]# lsattr /mnt/gfs2
/mnt/gfs2/gfs2_dir
~]# touch /mnt/gfs2/gfs2_dir/newfile
~]# lsattr /mnt/gfs2/gfs2_dir
/mnt/gfs2/gfs2_dir/newfile
3.9. Configuring atime Updat es
Each file inode and directory inode has three time stamps associated with it:
ctime — The last time the inode status was changed
mtime — The last time the file (or directory) data was modified
atime — The last time the file (or directory) data was accessed
If atime updates are enabled as they are by default on GFS2 and other Linux file systems then every
time a file is read, its inode needs to be updated.
Because few applications use the information provided by atime, those updates can require a
significant amount of unnecessary write traffic and file locking traffic. That traffic can degrade
performance; therefore, it may be preferable to turn off or reduce the frequency of atime updates.
To reduce the effects of atime updating, you can mount with the noatime option, which disables
atime updates on that file system. The noatime Linux mount option can be specified when the file
system is mounted, which disables atime updates on that file system.
Usage
mount BlockDevice MountPoint -o noatime
BlockDevice
Specifies the block device where the GFS2 file system resides.
MountPoint
Specifies the directory where the GFS2 file system should be mounted.
Example
32
Example
In this example, the GFS2 file system resides on the /dev/vg01/lvol0 and is mounted on directory
/mygfs2 with atime updates turned off.
mount /dev/vg01/lvol0 /mygfs2 -o noatime
3.10. Suspending Act ivit y on a File Syst em
You can suspend write activity to a file system by using the gfs2_tool freeze command.
Suspending write activity allows hardware-based device snapshots to be used to capture the file
system in a consistent state. The gfs2_tool unfreeze command ends the suspension.
Usage
St art Su sp en sio n
gfs2_tool freeze MountPoint
En d Su sp en sio n
gfs2_tool unfreeze MountPoint
MountPoint
Specifies the file system.
Examples
This example suspends writes to file system /mygfs2.
gfs2_tool freeze /mygfs2
This example ends suspension of writes to file system /mygfs2.
gfs2_tool unfreeze /mygfs2
3.11. Repairing a File Syst em
When nodes fail with the file system mounted, file system journaling allows fast recovery. However, if
a storage device loses power or is physically disconnected, file system corruption may occur.
(Journaling cannot be used to recover from storage subsystem failures.) When that type of corruption
occurs, you can recover the GFS2 file system by using the fsck.gfs2 command.
Important
The fsck.gfs2 command must be run only on a file system that is unmounted from all nodes.
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Important
You should not check a GFS2 file system at boot time with the fsck.gfs2 command. The
fsck.gfs2 command can not determine at boot time whether the file system is mounted by
another node in the cluster. You should run the fsck.gfs2 command manually only after the
system boots.
To ensure that the fsck.gfs2 command does not run on a GFS2 file system at boot time,
modify the /etc/fstab file so that the final two columns for a GFS2 file system mount point
show " 0 0" rather than " 1 1" (or any other numbers), as in the following example:
/dev/VG12/lv_svr_home
/svr_home
defaults,noatime,nodiratime,noquota
gfs2
0 0
Note
If you have previous experience using the gfs_fsck command on GFS file systems, note that
the fsck.gfs2 command differs from some earlier releases of gfs_fsck in the in the
following ways:
Pressing Ctrl+C while running the fsck.gfs2 interrupts processing and displays a
prompt asking whether you would like to abort the command, skip the rest of the current
pass, or continue processing.
You can increase the level of verbosity by using the -v flag. Adding a second -v flag
increases the level again.
You can decrease the level of verbosity by using the -q flag. Adding a second -q flag
decreases the level again.
The -n option opens a file system as read-only and answers no to any queries
automatically. The option provides a way of trying the command to reveal errors without
actually allowing the fsck.gfs2 command to take effect.
Refer to the fsck.gfs2 man page for additional information about other command options.
Running the fsck.gfs2 command requires system memory above and beyond the memory used for
the operating system and kernel. Each block of memory in the GFS2 file system itself requires
approximately five bits of additional memory, or 5/8 of a byte. So to estimate how many bytes of
memory you will need to run the fsck.gfs2 command on your file system, determine how many
blocks the file system contains and multiply that number by 5/8.
For example, to determine approximately how much memory is required to run the fsck.gfs2
command on a GFS2 file system that is 16TB with a block size of 4K, first determine how many blocks
of memory the file system contains by dividing 16Tb by 4K:
17592186044416 / 4096 = 4294967296
Since this file system contains 4294967296 blocks, multiply that number by 5/8 to determine how
many bytes of memory are required:
4294967296 * 5/8 = 2684354560
34
Usage
This file system requires approximately 2.6GB of free memory to run the fsck.gfs2 command. Note
that if the block size was 1K, running the fsck.gfs2 command would require four times the memory,
or approximately 11GB.
Usage
fsck.gfs2 -y BlockDevice
-y
The -y flag causes all questions to be answered with yes. With the -y flag specified, the
fsck.gfs2 command does not prompt you for an answer before making changes.
BlockDevice
Specifies the block device where the GFS2 file system resides.
Example
In this example, the GFS2 file system residing on block device /dev/testvol/testlv is repaired.
All queries to repair are automatically answered with yes.
[root@dash-01 ~]# fsck.gfs2 -y /dev/testvg/testlv
Initializing fsck
Validating Resource Group index.
Level 1 RG check.
(level 1 passed)
Clearing journals (this may take a while)...
Journals cleared.
Starting pass1
Pass1 complete
Starting pass1b
Pass1b complete
Starting pass1c
Pass1c complete
Starting pass2
Pass2 complete
Starting pass3
Pass3 complete
Starting pass4
Pass4 complete
Starting pass5
Pass5 complete
Writing changes to disk
fsck.gfs2 complete
3.12. Bind Mount s and Cont ext -Dependent Pat h Names
GFS2 file systems do not provide support for Context-D ependent Path Names (CD PNs), which allow
you to create symbolic links that point to variable destination files or directories. For this functionality
in GFS2, you can use the bind option of the mount command.
The bind option of the mount command allows you to remount part of a file hierarchy at a different
location while it is still available at the original location. The format of this command is as follows.
35
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
mount --bind olddir newdir
After executing this command, the contents of the olddir directory are available at two locations:
olddir and newdir. You can also use this option to make an individual file available at two
locations.
For example, after executing the following commands the contents of /root/tmp will be identical to
the contents of the previously mounted /var/log directory.
[root@menscryfa ~]# cd ~root
[root@menscryfa ~]# mkdir ./tmp
[root@menscryfa ~]# mount --bind /var/log /tmp
Alternately, you can use an entry in the /etc/fstab file to achieve the same results at mount time.
The following /etc/fstab entry will result in the contents of /root/tmp being identical to the
contents of the /var/log directory.
/var/log
/root/tmp
none
bind
0 0
After you have mounted the file system, you can use the mount command to see that the file system
has been mounted, as in the following example.
[root@menscryfa ~]# mount | grep /tmp
/var/log on /root/tmp type none (rw,bind)
With a file system that supports Context-D ependent Path Names, you might have defined the /bin
directory as a Context-D ependent Path Name that would resolve to one of the following paths,
depending on the system architecture.
/usr/i386-bin
/usr/x86_64-bin
/usr/ppc64-bin
You can achieve this same functionality by creating an empty /bin directory. Then, using a script or
an entry in the /etc/fstab file, you can mount each of the individual architecture directories onto
the /bin directory with a mount -bind command. For example, you can use the following
command as a line in a script.
mount --bind /usr/i386-bin /bin
Alternately, you can use the following entry in the /etc/fstab file.
/usr/1386-bin
/bin
none
bind
0 0
A bind mount can provide greater flexibility than a Context-D ependent Path Name, since you can use
this feature to mount different directories according to any criteria you define (such as the value of
%fill for the file system). Context-D ependent Path Names are more limited in what they can
encompass. Note, however, that you will need to write your own script to mount according to a criteria
such as the value of %fill.
36
Usage
Warning
When you mount a file system with the bind option and the original file system was mounted
rw, the new file system will also be mounted rw even if you use the ro flag; the ro flag is
silently ignored. In this case, the new file system might be marked as ro in the /proc/mounts
directory, which may be misleading.
3.13. Bind Mount s and File Syst em Mount Order
When you use the bind option of the mount command, you must be sure that the file systems are
mounted in the correct order. In the following example, the /var/log directory must be mounted
before executing the bind mount on the /tmp directory:
# mount --bind /var/log /tmp
The ordering of file system mounts is determined as follows:
In general, file system mount order is determined by the order in which the file systems appear in
the fstab file. The exceptions to this ordering are file systems mounted with the _netdev flag or
file systems that have their own init scripts.
A file system with its own init script is mounted later in the initialization process, after the file
systems in the fstab file.
File systems mounted with the _netdev flag are mounted when the network has been enabled on
the system.
If your configuration requires that you create a bind mount on which to mount a GFS2 file system,
you can order your fstab file as follows:
1. Mount local file systems that are required for the bind mount.
2. Bind mount the directory on which to mount the GFS2 file system.
3. Mount the GFS2 file system.
If your configuration requires that you bind mount a local directory or file system onto a GFS2 file
system, listing the file systems in the correct order in the fstab file will not mount the file systems
correctly since the GFS2 file system will not be mounted until the GFS2 init script is run. In this
case, you should write an init script to execute the bind mount so that the bind mount will not take
place until after the GFS2 file system is mounted.
The following script is an example of a custom init script. This script performs a bind mount of two
directories onto two directories of a GFS2 file system. In this example, there is an existing GFS2
mount point at /mnt/gfs2a, which is mounted when the GFS2 init script runs, after cluster startup.
In this example script, the values of the chkconfig statement indicate the following:
345 indicates the run levels that the script will be started in
29 is the start priority, which in this case indicates that the script will run at startup time after the
GFS2 init script, which has a start priority of 26
37
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
73 is the stop priority, which in this case indicates that the script will be stopped during shutdown
before the GFS2 script, which has a stop priority of 74
The start and stop values indicate that you can manually perform the indicated action by executing a
service start and a service stop command. For example, if the script is named fredwilma,
then you can execute service fredwilma start.
This script should be put in the /etc/init.d directory with the same permissions as the other
scripts in that directory. You can then execute a chkconfig on command to link the script to the
indicated run levels. For example, if the script is named fredwilma, then you can execute
chkconfig fredwilma on.
#!/bin/bash
#
# chkconfig: 345 29 73
# description: mount/unmount my custom bind mounts onto a gfs2 subdirectory
#
#
### BEGIN INIT INFO
# Provides:
### END INIT INFO
. /etc/init.d/functions
case "$1" in
start)
# In this example, fred and wilma want their home directories
# bind-mounted over the gfs2 directory /mnt/gfs2a, which has
# been mounted as /mnt/gfs2a
mkdir -p /mnt/gfs2a/home/fred &> /dev/null
mkdir -p /mnt/gfs2a/home/wilma &> /dev/null
/bin/mount --bind /mnt/gfs2a/home/fred /home/fred
/bin/mount --bind /mnt/gfs2a/home/wilma /home/wilma
;;
stop)
/bin/umount /mnt/gfs2a/home/fred
/bin/umount /mnt/gfs2a/home/wilma
;;
status)
;;
restart)
$0 stop
$0 start
;;
reload)
$0 start
;;
*)
echo $"Usage: $0 {start|stop|restart|reload|status}"
exit 1
esac
exit 0
3.14 . T he GFS2 Wit hdraw Funct ion
The GFS2 withdraw function is a data integrity feature of GFS2 file systems in a cluster. If the GFS2
38
Usage
kernel module detects an inconsistency in a GFS2 file system following an I/O operation, the file
system becomes unavailable to the cluster. The I/O operation stops and the system waits for further
I/O operations to stop with an error, preventing further damage. When this occurs, you can stop any
other services or applications manually, after which you can reboot and remount the GFS2 file
system to replay the journals. If the problem persists, you can unmount the file system from all nodes
in the cluster and perform file system recovery with the fsck.gfs2 command. The GFS withdraw
function is less severe than a kernel panic, which would cause another node to fence the node.
If your system is configured with the gfs2 startup script enabled and the GFS2 file system is included
in the /etc/fstab file, the GFS2 file system will be remounted when you reboot. If the GFS2 file
system withdrew because of perceived file system corruption, it is recommended that you run the
fsck.gfs2 command before remounting the file system. In this case, in order to prevent your file
system from remounting at boot time, you can perform the following procedure:
1. Temporarily disable the startup script on the affected node with the following command:
# chkconfig gfs2 off
2. Reboot the affected node, starting the cluster software. The GFS2 file system will not be
mounted.
3. Unmount the file system from every node in the cluster.
4. Run the fsck.gfs2 on the file system from one node only to ensure there is no file system
corruption.
5. Re-enable the startup script on the affected node by running the following command:
# chkconfig gfs2 on
6. Remount the GFS2 file system from all nodes in the cluster.
An example of an inconsistency that would yield a GFS2 withdraw is an incorrect block count. When
the GFS kernel deletes a file from a file system, it systematically removes all the data and metadata
blocks associated with that file. When it is done, it checks the block count. If the block count is not
one (meaning all that is left is the disk inode itself), that indicates a file system inconsistency since
the block count did not match the list of blocks found.
You can override the GFS2 withdraw function by mounting the file system with the -o
errors=panic option specified. When this option is specified, any errors that would normally cause
the system to withdraw cause the system to panic instead. This stops the node's cluster
communications, which causes the node to be fenced.
Internally, the GFS2 withdraw function works by having the kernel send a message to the
gfs_controld daemon requesting withdraw. The gfs_controld daemon runs the dmsetup
program to place the device mapper error target underneath the filesystem preventing further access
to the block device. It then tells the kernel that this has been completed. This is the reason for the
GFS2 support requirement to always use a CLVM device under GFS2, since otherwise it is not
possible to insert a device mapper target.
The purpose of the device mapper error target is to ensure that all future I/O operations will result in
an I/O error that will allow the filesystem to be unmounted in an orderly fashion. As a result, when the
withdraw occurs, it is normal to see a number of I/O errors from the device mapper device reported in
the system logs.
Occasionally, the withdraw may fail if it is not possible for the dmsetup program to insert the error
target as requested. This can happen if there is a shortage of memory at the point of the withdraw
and memory cannot be reclaimed due to the problem that triggered the withdraw in the first place.
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Red Hat Ent erprise Linux 5 G lobal File Syst em 2
A withdraw does not always mean that there is an error in GFS2. Sometimes the withdraw function
can be triggered by device I/O errors relating to the underlying block device. It is highly
recommended to check the logs to see if that is the case if a withdraw occurs.
40
Convert ing a File Syst em from G FS t o G FS2
Converting a File System from GFS to GFS2
Use the gfs2_convert command. To convert a GFS file system to a GFS2 file system.
Warning
Before converting the GFS file system, you must back up the file system, since the conversion
process is irreversible and any errors encountered during the conversion can result in the
abrupt termination of the program and consequently an unusable file system.
Before converting the GFS file system, you must use the gfs_fsck command to check the file
system and fix any errors.
If the conversion from GFS to GFS2 is interrupted by a power failure or any other issue, restart
the conversion tool. D o not attempt to execute the fsck.gfs2 command on the file system
until the conversion is complete.
Context-Dependent Path Names
GFS2 file systems do not provide support for Context-D ependent Path Names (CD PNs), which
allow you to create symbolic links that point to variable destination files or directories. To
achieve the same functionality as CD PNs in GFS2 file systems, you can use the bind option
of the mount command.
The gfs2_convert command identifies CD PNs and replaces them with empty directories with
the same name. In order to configure bind mounts to replace the CD PNs, however, you need to
know the full paths of the link targets of the CD PNs you are replacing. Before converting your
file system, you can use the find command to identify the links.
The following command lists the symlinks that point to a hostname CD PN:
[root@smoke-01 gfs]# find /mnt/gfs -lname @hostname
/mnt/gfs/log
Similarly, you can execute the find command for other CD PNs (mach, os, sys, uid, gid,
jid). Note that since CD PN names can be of the form @hostname or {hostname}, you will
need to run the find command for each variant.
For more information on bind mounts and context-dependent pathnames in GFS2, see
Section 3.12, “ Bind Mounts and Context-D ependent Path Names” .
When converting full or nearly full file systems, it is possible that there will not be enough space
available to fit all the GFS2 file system data structures. In such cases, the size of all the journals is
reduced uniformly such that everything fits in the available space.
1. Make a backup of your existing GFS file system.
2. Unmount the GFS file system from all nodes in the cluster.
41
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
3. Execute the gfs_fsck command on the GFS file system to ensure there is no file system
corruption.
4. Execute gfs2_convert gfsfilesystem. The system will display warnings and
confirmation questions before converting gfsfilesystem to GFS2.
The following example converts a GFS filesystem on block device /dev/shell_vg/500g to a GFS2
filesystem.
[root@shell-01 ~]# /root/cluster/gfs2/convert/gfs2_convert /dev/shell_vg/500g
gfs2_convert version 2 (built May 10 2010 10:05:40)
Copyright (C) Red Hat, Inc. 2004-2006 All rights reserved.
Examining file system..................
This program will convert a gfs1 filesystem to a gfs2 filesystem.
WARNING: This can't be undone. It is strongly advised that you:
1. Back up your entire filesystem first.
2. Run gfs_fsck first to ensure filesystem integrity.
3. Make sure the filesystem is NOT mounted from any node.
4. Make sure you have the latest software versions.
Convert /dev/shell_vg/500g from GFS1 to GFS2? (y/n)y
Converting resource groups...................
Converting inodes.
24208 inodes from 1862 rgs converted.
Fixing file and directory information.
18 cdpn symlinks moved to empty directories.
Converting journals.
Converting journal space to rg space.
Writing journal #1...done.
Writing journal #2...done.
Writing journal #3...done.
Writing journal #4...done.
Building GFS2 file system structures.
Removing obsolete GFS1 file system structures.
Committing changes to disk.
/dev/shell_vg/500g: filesystem converted successfully to gfs2.
42
Revision Hist ory
Revision History
R evisio n 9 .0- 7
Version for 5.11 GA release
Mo n Sep 8 2014
St even Levin e
R evisio n 9 .0- 5
T u e Ju l 1 2014
Beta release of Red Hat Enterprise Linux 5.11
St even Levin e
R evisio n 9 .0- 3
Mo n Ju n 30 2014
Test build for Red Hat Enterprise Linux 5.11 release
St even Levin e
R evisio n 8.0- 7
Mo n Sep 30 2013
Version for Red Hat Enterprise Linux 5.10 GA release
St even Levin e
R evisio n 8.0- 5
Wed Ju l 10 2013
Beta release of Red Hat Enterprise Linux 5.10
St even Levin e
R evisio n 8.0- 4
Resolves: #965843
Clarifies support issues.
St even Levin e
T u e May 28 2013
R evisio n 8.0- 3
Wed May 22 2013
St even Levin e
Restoring reference to extended attributes from Overview, but without reference to SELinux as per
BZ #965843.
R evisio n 8.0- 2
T u e May 21 2013
Removing reference to SELinux attributes from Overview
St even Levin e
R evisio n 7.0- 3
Fri Jan 4 2013
Version for Red Hat Enterprise Linux 5.9 GA release
St even Levin e
R evisio n 7.0- 2
Wed Au g 29 2012
Beta release of Red Hat Enterprise Linux 5.9
St even Levin e
R evisio n 6 .0- 3
T h u Feb 16 2012
Release for GA of Red Hat Enterprise Linux 5.8
St even Levin e
R evisio n 6 .0- 2
T h u D ec 15 2011
Beta release of Red Hat Enterprise Linux 5.8
St even Levin e
R evisio n 6 .0- 1
T h u N o v 10 2011
Resolves: #758841
Notes CLVM requirement for clustered environment.
St even Levin e
Resolves: #736156
Adds note warning not to check a GFS2 file system at boot time.
Resolves: #750328
Corrects small typographical errors.
R evisio n 5.0- 1
T h u Ju l 21 2011
St even Levin e
43
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
Resolves: #664848
Updates documentation of GFS to GFS2 conversion process to clarify procedure for replacing
Context-D ependent Path Names.
Resolves: #676131
Clarifies section on the withdraw function.
Resolves: #654490
Corrects minor typos.
R evisio n 4 .0- 1
T h u D ec 23 2010
Resolves: #661519
Corrects maximum file system size numbers.
St even Levin e
Resolves: #588374
Updates gfs2_convert documentation appendix.
Resolves: #606224
Removes relatime documentation.
R evisio n 3.0- 2
T u e Au g 3 2010
St even Levin e
Resolves: #562251
Adds information about the localflocks mount option and when it may be required.
R evisio n 3.0- 1
T h u Mar 11 2010
St even Levin e
Resolves: #546687
D ocuments features for the Red Hat Enterprise Linux 5.5 release.
Resolves: #568179
Adds note clarifying support policy for single-node system.
Resolves: #562199
Adds note clarifying 16-node limitation.
Resolves: #515348
D ocuments new -o errors mount option.
Resolves: #573750
D ocuments memory requirements for fsck.gfs2.
Resolves: #574470
Clarifies issue of gfs2 requiring CLVM for Red Hat support.
R evisio n 2.0- 1
44
T u e Au g 18 2009
St even Levin e
⁠Index
Resolves: #515807
Adds note clarifying that you cannot reduce the size of an existing file system.
Resolves: #480002
Adds caveat about unmounting a file system manually if you mounted it manually, adds section on
bind mounting a non-GFS2 file system to a GFS2 file system, adds sample custom init script.
Resolves: #458604
Adds section on GFS2 withdraw function.
Resolves: #498292
Clarifies documentation on adding journals.
R evisio n 1.0- 1
T h u Jan 29 2009
Index
A
acl mo u n t o p t io n , Mo u n t in g a File Syst em
ad d in g jo u rn als t o a f ile syst em, Ad d in g Jo u rn als t o a File Syst em
at ime, co n f ig u rin g u p d at es, C o n f ig u rin g at ime U p d at es
- mounting with noatime , Configuring atime Updates
au d ien ce, Au d ien ce
B
b in d mo u n t
- mount order, Bind Mounts and File System Mount Order
b in d mo u n t s, B in d Mo u n t s an d C o n t ext - D ep en d en t Pat h N ames
C
co n f ig u rat io n , b ef o re, B ef o re Set t in g U p G FS2
co n f ig u rat io n , in it ial, G et t in g St art ed
- prerequisite tasks, Prerequisite Tasks
D
d at a jo u rn alin g , D at a Jo u rn alin g
F
f eed b ack, Feed b ack
f ile syst em
- adding journals, Adding Journals to a File System
- atime, configuring updates, Configuring atime Updates
- mounting with noatime , Configuring atime Updates
- bind mounts, Bind Mounts and Context-D ependent Path Names
- context-dependent path names (CD PNs), Bind Mounts and Context-D ependent Path
Names
45
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
- data journaling, D ata Journaling
- growing, Growing a File System
- making, Making a File System
- mount order, Bind Mounts and File System Mount Order
- mounting, Mounting a File System, Special Considerations when Mounting GFS2
File Systems
- quota management, GFS2 Quota Management
- displaying quota limits, D isplaying Quota Limits and Usage
- enabling quota accounting, Enabling Quota Accounting
- enabling/disabling quota enforcement, Enabling/D isabling Quota
Enforcement
- setting quotas, Setting Quotas
- synchronizing quotas, Synchronizing Quotas
- repairing, Repairing a File System
- suspending activity, Suspending Activity on a File System
- unmounting, Unmounting a File System, Special Considerations when Mounting
GFS2 File Systems
f sck.g f s2 co mman d , R ep airin g a File Syst em
G
G FS2
- atime, configuring updates, Configuring atime Updates
- mounting with noatime , Configuring atime Updates
- managing, Managing GFS2
- quota management, GFS2 Quota Management
- displaying quota limits, D isplaying Quota Limits and Usage
- enabling quota accounting, Enabling Quota Accounting
- enabling/disabling quota enforcement, Enabling/D isabling Quota
Enforcement
- setting quotas, Setting Quotas
- synchronizing quotas, Synchronizing Quotas
- withdraw function, The GFS2 Withdraw Function
G FS2 f ile syst em maximu m siz e, G FS2 O verview
G FS2- sp ecif ic o p t io n s f o r ad d in g jo u rn als t ab le, C o mp let e U sag e
G FS2- sp ecif ic o p t io n s f o r exp an d in g f ile syst ems t ab le, C o mp let e U sag e
g f s2_g ro w co mman d , G ro win g a File Syst em
g f s2_jad d co mman d , Ad d in g Jo u rn als t o a File Syst em
g f s2_q u o t a co mman d , G FS2 Q u o t a Man ag emen t
g ro win g a f ile syst em, G ro win g a File Syst em
I
in it ial t asks
- setup, initial, Initial Setup Tasks
in t ro d u ct io n , In t ro d u ct io n
- audience, Audience
M
46
⁠Index
makin g a f ile syst em, Makin g a File Syst em
man ag in g G FS2, Man ag in g G FS2
maximu m siz e, G FS2 f ile syst em, G FS2 O verview
mkf s co mman d , Makin g a File Syst em
mkf s.g f s2 co mman d o p t io n s t ab le, C o mp let e O p t io n s
mo u n t co mman d , Mo u n t in g a File Syst em
mo u n t t ab le, C o mp let e U sag e
mo u n t in g a f ile syst em, Mo u n t in g a File Syst em, Sp ecial C o n sid erat io n s wh en
Mo u n t in g G FS2 File Syst ems
O
o verview, G FS2 O verview
- configuration, before, Before Setting Up GFS2
P
p at h n ames, co n t ext - d ep en d en t ( C D PN s) , B in d Mo u n t s an d C o n t ext - D ep en d en t
Pat h N ames
p ref ace ( see in t ro d u ct io n )
p rereq u isit e t asks
- configuration, initial, Prerequisite Tasks
Q
q u o t a man ag emen t , G FS2 Q u o t a Man ag emen t
- displaying quota limits, D isplaying Quota Limits and Usage
- enabling quota accounting, Enabling Quota Accounting
- enabling/disabling quota enforcement, Enabling/D isabling Quota Enforcement
- setting quotas, Setting Quotas
- synchronizing quotas, Synchronizing Quotas
q u o t a= mo u n t o p t io n , Set t in g Q u o t as
q u o t a_q u an t u m t u n ab le p aramet er, Syn ch ro n iz in g Q u o t as
R
rep airin g a f ile syst em, R ep airin g a File Syst em
S
set u p , in it ial
- initial tasks, Initial Setup Tasks
su sp en d in g act ivit y o n a f ile syst em, Su sp en d in g Act ivit y o n a File Syst em
syst em h an g at u n mo u n t , Sp ecial C o n sid erat io n s wh en Mo u n t in g G FS2 File
Syst ems
T
t ab les
-
GFS2-specific options for adding journals, Complete Usage
GFS2-specific options for expanding file systems, Complete Usage
mkfs.gfs2 command options, Complete Options
mount options, Complete Usage
47
Red Hat Ent erprise Linux 5 G lobal File Syst em 2
U
u mo u n t co mman d , U n mo u n t in g a File Syst em
u n mo u n t , syst em h an g , Sp ecial C o n sid erat io n s wh en Mo u n t in g G FS2 File Syst ems
u n mo u n t in g a f ile syst em, U n mo u n t in g a File Syst em, Sp ecial C o n sid erat io n s wh en
Mo u n t in g G FS2 File Syst ems
W
wit h d raw f u n ct io n , G FS2, T h e G FS2 Wit h d raw Fu n ct io n
48
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