Learn Linux, 101: Manage disk quotas

Overview

In this article, learn to manage disk quotas for users. Learn to:

• Set up a disk quota for a filesystem
• Set quota limits
• Check quotas
• Generate quota reports

Unless otherwise noted, the examples in this article use Fedora 13 with a 2.6.34 kernel. Your results on other systems may differ.

This article helps you prepare for Objective 104.4 in Topic 104 of the Linux Professional Institute's Junior Level Administration (LPIC-1) exam 101. The objective has a weight of 1.

Prerequisites

To get the most from the articles in this series, you should have a basic knowledge of Linux and a working Linux system on to practice the commands covered in this article. Sometimes different versions of a program will format output differently, so your results may not always look exactly like the listings and figures shown here.

You should also be familiar with the material in our article "Learn Linux 101: Create partitions and filesystems."

Introducing quotas

Quotas allow you to control disk usage by user or by group. Quotas prevent individual users and groups from using a larger portion of a filesystem than they are permitted, or from filling it up altogether. XFS filesystems also support project quotas, which limit the amount of space used by a project, regardless of which users create files in the project's directory tree.

Quotas must be enabled and managed by the root user or by a user with root authority. They are often used on multiuser systems, but less often on single-user workstations.

There are three different types of quota support:

1. vfsold, or version 1 quota
2. vfsv0, or version 2 quota
3. xfs, the quota on XFS filesystems

This article covers version 2 quota on non-XFS filesystems and xfs quota on XFS filesystems. Note that the LPI 101 exam focuses on version 2 quotas.

Quotas require kernel support that was introduced in later 2.4 kernels. 2.6 kernels have the support you need.

XFS quotas are always journaled. Journaled version 2 quotas are supported on kernel 2.6.11 and above.

Our test setup

So that you can better understand some of the examples, we will first describe the test partition setup we are using for this article. If you already understand file ownership and permissions, and you have the quota package already installed, you may skip to the Enabling quotas section. Refer to our IBM Developer roadmap for LPIC-1 for links to other articles in this series that provide more detail about these commands than the brief explanations provided here.

Test partitions and users

We use a 110GB ext4 partition (/dev/sda7) and a 40GB XFS partition (/dev/sda8) for demonstration purposes. These are mounted at /quotatest/ext4 and /quotatest/xfs, respectively.

Listing 1. Setting up the partitions

[root@echidna ~]# mkfs -t ext4 /dev/sda7
mke2fs 1.41.10 (10-Feb-2009)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
7159808 inodes, 28637862 blocks
1431893 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
874 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@echidna ~]# mkfs -t xfs /dev/sda8
meta-data=/dev/sda8              isize=256    agcount=4, agsize=2622108 blks
         =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=10488429, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal log           bsize=4096   blocks=5121, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
[root@echidna ~]# mkdir -p /quotatest/ext4
[root@echidna ~]# mkdir -p /quotatest/xfs
[root@echidna ~]# mount /dev/sda7 /quotatest/ext4
[root@echidna ~]# mount /dev/sda8 /quotatest/xfs

For this example. we want regular users to be able to create files in the new filesystems. As created, the filesystems are owned by root, and normal users cannot create files or directories on them. We will change the ownership so that the new filesystems are owned by user development who has a private group also called development. We will also change the permissions so that users in the development group can create files and directories. Listing 2 shows how we have set up the ownership and permissions.

Listing 2. Changing ownership and permissions for our test partitions

[root@echidna ~]# # Show default ownership and permissions
[root@echidna ~]# ls -l /quotatest/
total 4
drwxr-xr-x. 3 root root 4096 Nov 18 22:43 ext4
drwxr-xr-x. 2 root root    6 Nov 18 22:43 xfs
[root@echidna ~]# # Change user and group ownership to development
[root@echidna ~]# chown development:development /quotatest/*
[root@echidna ~]# # Allow group members to create files and directories
[root@echidna ~]# chmod g+w /quotatest/*
[root@echidna ~]# ls -l /quotatest/
total 4
drwxrwxr-x. 3 development development 4096 Nov 18 22:43 ext4
drwxrwxr-x. 2 development development    6 Nov 18 22:43 xfs
[root@echidna ~]# # Set default group of new files and directories
[root@echidna ~]# # to development
[root@echidna ~]# chmod g+s /quotatest/ext4/
[root@echidna ~]# ls -l /quotatest/
total 4
drwxrwsr-x. 3 development development 4096 Nov 19 11:39 ext4
drwxrwxr-x. 2 development development    6 Nov 18 22:43 xfs

We also make use of three users, ian, gretchen, and tom, each having a private group with the same name as the user name. Each of these users is also a member of the development group.

Checking for the quota package

If you are using a desktop system, you may not have the quota package installed since quotas are not part of the usual default desktop install. Use dpkg or rpm to check that you have the package installed as shown in Checking for quota packages.

Listing 3. Checking for quota packages

# On Debian-based systems
ian@pinguino:~$ dpkg -l quota
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-============================================
ii  quota          4.00~pre1-3    implementation of the disk quota system

# On systems that use RPM
[ian@echidna ~]$ rpm -q quota
quota-3.17-11.fc13.x86_64

If you do not have the quota package installed already see our articles, "Learn Linux 101: Use Debian package management." and Learn Linux 101: Use RPM and YUM package management for help on installing packages.

Enabling quotas

Adding quota support to /etc/fstab

The next step to enable quotas is to add the appropriate options to the filesystem definitions in /etc/fstab, according to whether you want to implement user quotas, group quotas, or both. XFS filesystems also support project quotas.

At the time of writing, the options for enabling quotas are not centrally documented in an obvious man page. Quota options in /etc/fstab shows the options that are available and the type of quota system they are used for.

Listing 4. Quota options in /etc/fstab

We use an ext4 partition and an XFS partition for demonstration purposes. We'll add user and group quota to these filesystems so you can see how quotas work on two different filesystems. Our /etc/fstab entries are shown in Enabling quota support in /etc/fstab.

Listing 5. Enabling quota support in /etc/fstab

/dev/sda7  /quotatest/ext4  ext4    defaults,usrquota,grpquota          1 2
/dev/sda8  /quotatest/xfs   xfs     defaults,usrquota,grpquota          1 2

Remount the filesystem

After you edit /etc/fstab and add quotas, you need to remount the filesystems. For XFS filesystems, quota data is considered part of the filesystem metadata. For other filesystems, user quota information is stored in the aquota.user file in the root of the filesystem, and group quota is similarly stored in aquota.group. Version 1 quotas used quota.user and quota.group. For these filesystems, after you remount the filesystem, you must create the quota files and enable quota checking. The quotacheck command checks the quotas on all filesystems and creates the required aquota.user and aquota.group files if they do not exist. It can also repair damaged quota files. See the man pages for more information.

The following are some of the common options used with the quotacheck command:

• -a or --all: Check all mounted filesystems in /etc/mtab (except NFS filesystems)
• -c or --create-files: Ignore existing quota files. Run a new scan and write the results to disk
• -u or --user: Check user quotas (this is the default)
• -g or --group: Check group quotas
• -v or --verbose: Verbose output

Creating quota database files for vfsold and vfsv0 shows the result of running the quotacheck command on our freshly remounted filesystems. If you do not use the -a option, you must specify the filesystem that you want to check.

Listing 6. Creating quota database files for vfsold and vfsv0

[root@echidna ~]# quotacheck -augvc
quotacheck: Skipping /dev/sda8 [/quotatest/xfs]
quotacheck: Your kernel probably supports journaled quota but you are not using it.
Consider switching to journaled quota to avoid running quotacheck after an unclean
shutdown.
quotacheck: Scanning /dev/sda7 [/quotatest/ext4] done
quotacheck: Cannot stat old user quota file: No such file or directory
quotacheck: Cannot stat old group quota file: No such file or directory
quotacheck: Cannot stat old user quota file: No such file or directory
quotacheck: Cannot stat old group quota file: No such file or directory
quotacheck: Checked 2 directories and 1 files
quotacheck: Old file not found.
quotacheck: Old file not found.

Notice the warning from the quotacheck command suggesting that we switch to using journaled quotas. Do this by changing the options in /etc/fstab for the ext4 filesystem on /dev/sda7 from

defaults,usrquota,grpquota

to

defaults,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0

Notice also that the XFS filesystem was skipped by the quotacheck command because the XFS quota structures are contained in the meta-data and journaled.

Start or stop quota checking

To enforce vfsold and vfsv0 quota checking, you must turn it on using the quotaon command. The common options -a, -g, -u, and -v have the same meaning as for the quotacheck command. Similarly, if you do not specify the -a option, you must specify a filesystem. Use the -p option if you just want to display whether quotas are on or off. Use the quotaoff command to turn off quota checking. Turning on quota checking for vfsold and vfsv0 quotas shows examples of both these commands.

Listing 7. Turning on quota checking for vfsold and vfsv0 quotas

[root@echidna ~]# quotaon -p /quotatest/ext4/
group quota on /quotatest/ext4 (/dev/sda7) is off
user quota on /quotatest/ext4 (/dev/sda7) is off
[root@echidna ~]# quotaon -uagv
/dev/sda7 [/quotatest/ext4]: group quotas turned on
/dev/sda7 [/quotatest/ext4]: user quotas turned on
[root@echidna ~]# quotaoff -ugv /quotatest/ext4/
/dev/sda7 [/quotatest/ext4]: group quotas turned off
/dev/sda7 [/quotatest/ext4]: user quotas turned off
[root@echidna ~]# quotaon -ugv /quotatest/ext4/
/dev/sda7 [/quotatest/ext4]: group quotas turned on
/dev/sda7 [/quotatest/ext4]: user quotas turned on

For XFS filesystems, quota checking is turned on by default, unless the file is mounted with the uqnoenforce, gqnoenforce, or pqnoenforce options. Use the xfs_quota command with the -x (for expert) option to manipulate xfs quotas. Without the -x option you are limited to displaying quota information. The command has several subcommands, including help to display a list of available subcommands, state to display overall state, enable to enable quota checking, and disable to disable it. The options -u, -g, and -p limit the action to users, groups, or projects, respectively. Use -v for verbose output. You can also run the command in command-line mode where the individual subcommand is specified with the -c option. You may specify this option multiple times for multiple subcommands. If you are specifying options for your subcommand, you will probably need to quote your command. Some examples are shown in listing 7.

Listing 8. Turning on quota checking for xfs quotas

[root@echidna ~]# xfs_quota -x
xfs_quota> state
User quota state on /quotatest/xfs (/dev/sda8)
  Accounting: ON
  Enforcement: ON
  Inode: #131 (3 blocks, 3 extents)
Group quota state on /quotatest/xfs (/dev/sda8)
  Accounting: ON
  Enforcement: ON
  Inode: #132 (3 blocks, 3 extents)
Project quota state on /quotatest/xfs (/dev/sda8)
  Accounting: OFF
  Enforcement: OFF
  Inode: #132 (3 blocks, 3 extents)
Blocks grace time: [7 days 00:00:30]
Inodes grace time: [7 days 00:00:30]
Realtime Blocks grace time: [7 days 00:00:30]
xfs_quota> disable
xfs_quota> quit
[root@echidna ~]# xfs_quota -x  -c "enable -gu -v"  /quotatest/xfs
User quota state on /quotatest/xfs (/dev/sda8)
  Accounting: ON
  Enforcement: ON
  Inode: #131 (3 blocks, 3 extents)
Group quota state on /quotatest/xfs (/dev/sda8)
  Accounting: ON
  Enforcement: ON
  Inode: #132 (3 blocks, 3 extents)
Blocks grace time: [7 days 00:00:30]
Inodes grace time: [7 days 00:00:30]
Realtime Blocks grace time: [7 days 00:00:30]

Checking vfsold and vfsv0 quotas on boot

Although beyond the scope of this article, the quotacheck and quotaon commands are usually included in initialization scripts so that quotas are enabled whenever you reboot the system. The Quota Mini HOWTO (see Resources for a link) has additional information. If you are using journaled quotas, you should not need to run quotacheck at boot time.

Setting quota limits

As you have seen, quotas are controlled either through binary files in the root of the filesystem or through filesystem metadata. To set a quota for a particular user, use the edquota command. This command extracts the quota information for the user from the various filesystems with quotas enabled, creates a temporary file, and opens an editor for you to adjust the quotas. By default, edquota uses the vi editor. Set the EDITOR or the VISUAL environment variables if you want to use a different editor. To edit user quotas, use the -u option (default) with one or more user names. To edit group quotas, use the -g with one or more group names.

You must be root to edit quotas. Using vi as the editor, the information displayed will look something like Running edquota.

Listing 9. Running edquota

Disk quotas for user ian (uid 1000):
  Filesystem                   blocks       soft       hard     inodes     soft     hard
  /dev/sda7                         0          0          0          0        0        0
  /dev/sda8                         0          0          0          0        0        0
~
~

As you can see in Running edquota, edquota displays my current usage of both 1K blocks and inodes on each of the filesystems that have quota turned on. There are also soft and hard limits for both block and inode usage. In this example, these are 0, meaning no quota limit is enforced.

The soft limit is the value at which a user will receive email warnings about being over quota. The hard limit is the value that a user may not exceed. You can think of block limits as an approximate limit on the amount of data that a user may store, and inode limits as a limit on the number of files and directories.

Changing quota limits

You change the quota limits by changing the values in the temporary file and then saving the file. If you do not want to make changes, quit the file without saving. We will use some very small limits in our examples, so you can easily see the effects. Suppose you want to set my quota to 10MB of data and 50 files on each of our test filesystems. Allowing 10% additional for hard limits, you would set values as shown in Setting limits.

Listing 10. Setting limits

Disk quotas for user ian (uid 1000):
  Filesystem                   blocks       soft       hard     inodes     soft     hard
  /dev/sda7                         0      10240      11264          0       50       55
  /dev/sda8                         0      10240      11264          0       50       55

Save the file, and the new quotas will take effect. Note that any changes you make to the used blocks or inodes values will be ignored.

Copying quotas

Now suppose you are creating ids for additional developers. Assume you have users gretchen and tom, and you'd like them both to have the same quota as ian. You do this using the -p option of edquota, which uses the quota values of ian as a prototype for those of the other users as shown in Setting quotas from a prototype.

Listing 11. Setting quotas from a prototype

root@pinguino:~# edquota -p ian gretchen tom

Group limits

You can also use edquota to restrict the allocation of disk space based on the group ownership of files. For example, the three developers above are members of the development group. To limit the total amounts used by the all members of the group to 250MB and 100 files, use the command edquota -g development and set the values as shown in Setting quotas for a group.

Listing 12. Setting quotas for a group

Disk quotas for group development (gid 505):
  Filesystem                   blocks       soft       hard     inodes     soft     hard
  /dev/sda7                         4      25600      28160          1      100      110
  /dev/sda8                         0      25600      28160          0      100      110

You may wonder why there are already some blocks and inodes used on /dev/sda7, our ext4 filesystem. Remember back in Changing ownership and permissions for our test partitions we used chown and chmod to set the default group for all new files to be the development group? That also applies to the two quota database files. You can change these back to being in root's group as shown in Resetting group owner for quota database files. Be sure to turn off quota checking to make the change and then turn it back on again.

Listing 13. Resetting group owner for quota database files

[root@echidna ~]# quotaoff /quotatest/ext4/
[root@echidna ~]# chown :root /quotatest/ext4/aquota.*
[root@echidna ~]# quotaon /quotatest/ext4/

The grace period

Users or groups may exceed their soft limit for a grace period, which defaults to 7 days. After the grace period, the soft limit is enforced as a hard limit. Once the hard limit is reached, some files must be deleted before new files can be created. Set grace periods with the -t option of edquota. Again, you will be placed in an editor with data similar to that of Setting grace periods. As before, save changes to update the values. Be sure to leave your users enough time to receive their warning email and delete some files accordingly.

Listing 14. Setting grace periods

Grace period before enforcing soft limits for users:
Time units may be: days, hours, minutes, or seconds
  Filesystem             Block grace period     Inode grace period
  /dev/sda7                     7days                  7days
  /dev/sda8                     7days                  7days

Checking quotas

The quota command with no options displays the quotas for the invoking user on any filesystems for which the user has quotas set if the user has files on that system. The -v option displays the information for all filesystems that have quota enabled. The root user may also add a user name to the command to view quotas for a particular user. In Displaying quotas, we create a 1MB file on our ext4 filesystem and show the use of the quota command with and without the -v option.

Listing 15. Displaying quotas

[ian@echidna ~]$ dd if=/dev/zero of=/quotatest/ext4/ianfile1 bs=1024 count=1024
1024+0 records in
1024+0 records out
1048576 bytes (1.0 MB) copied, 0.00793796 s, 132 MB/s
[ian@echidna ~]$ quota
Disk quotas for user ian (uid 1000):
     Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
      /dev/sda7    1024   10240   11264               1      50      55
[ian@echidna ~]$ quota -v
Disk quotas for user ian (uid 1000):
     Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
      /dev/sda7    1024   10240   11264               1      50      55
      /dev/sda8       0   10240   11264               0      50      55

Along with the statistics on current usage, you see the soft and hard quota limits displayed. If you run the quota command immediately after creating the file, you may see a slightly larger block count displayed for a short time. Exceeding quotas shows what happens if you exceed the soft limit and then what happens if you attempt to exceed the hard limit. In this example, we add a 9.5MB file to the 1MB we already created, which is sufficient to exceed the soft limit. Notice how the soft limit has an asterisk beside it indicating that the user is over quota. Note also that the grace period columns now indicate how long the user has to correct the problem. Finally, when we try to make a copy of the 1MB file, the operation fails because this would exceed the hard limit for user ian.

Listing 16. Exceeding quotas

[ian@echidna ~]$ dd if=/dev/zero of=/quotatest/ext4/ianfile2 bs=1024 count=9500
9500+0 records in
9500+0 records out
9728000 bytes (9.7 MB) copied, 0.0754223 s, 129 MB/s
[ian@echidna ~]$ quota
Disk quotas for user ian (uid 1000):
     Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
      /dev/sda7   10552*  10240   11264   7days       2      50      55
[ian@echidna ~]$ cp /quotatest/ext4/ianfile1 /quotatest/ext4/ianfile3
cp: writing `/quotatest/ext4/ianfile3': Disk quota exceeded

Quota reports

Checking user quotas one user at a time is not very useful, so you will want to use the repquota command to generate quota reports. Generating quota reports shows how to see the quotas for all users and groups on /quotatest/ext4/.

Listing 17. Generating quota reports

[root@echidna ~]# repquota -ug /quotatest/ext4/
*** Report for user quotas on device /dev/sda7
Block grace time: 7days; Inode grace time: 7days
                        Block limits                File limits
User            used    soft    hard  grace    used  soft  hard  grace
----------------------------------------------------------------------
root      --      24       0       0              2     0     0
ian       +-   11260   10240   11264  6days       3    50    55
gretchen  --    2080   10240   11264             44    50    55
tom       -+     660   10240   11264             55    50    55  6days
development --       4       0       0              1     0     0

*** Report for group quotas on device /dev/sda7
Block grace time: 7days; Inode grace time: 7days
                        Block limits                File limits
Group           used    soft    hard  grace    used  soft  hard  grace
----------------------------------------------------------------------
root      --      24       0       0              2     0     0
development -+   14004   25600   28160            103   100   110  7days

Note the plus sign in Generating quota reports for users ian and tom and for group development indicating that each is now over quota. User ian has too much data. User tom has too many files. And group development also has too many files.

As with other quota commands, the -a option produces a report for all mounted filesystems that have quota enabled. The -v option produces more verbose output. And the -n option produces the listing by numeric user number rather than resolving the user number to a name. This may provide a performance boost for large reports, but is generally less useful to human readers.

Project quotas on XFS filesystems

The xfs quota system also supports project quotas, which are an alternative to group quotas. You cannot use both group and project quotas on one XFS filesystem. Project quotas must be enabled by adding the prjquota (or pquota) to /etc/fstab.

Project quotas use the notion of a numeric id and a more descriptive project name. The file /etc/projects is used to map the numeric project identifiers to directory trees, while the file /etc/projid maps the numeric project identifiers to project names. It is possible, but less convenient, to operate without these two files in /etc. See the man pages for details.

To set project quotas, you must use the xfs_quota command in expert mode (-x option). First you must use the project subcommand with the -s option to set up the project quotas by marking all the affected inodes as part of the project. You then use the limit subcommand to set hard or soft limits. Setting up an xfs project quota shows how to set up a project tree under /quotatest/xfs/proj-dir1, with a 15MB project hard limit. We will also set up a parallel /quotatest/xfs/proj-dir2 with no limits for illustration.

Listing 18. Setting up an xfs project quota

[root@echidna ~]# mkdir -m ag+w /quotatest/xfs/proj-dir{1,2}
[root@echidna ~]# chown development:development /quotatest/xfs/proj-dir*
[root@echidna ~]# echo "50:/quotatest/xfs/proj-dir1" >> /etc/projects
[root@echidna ~]# echo "dev-projects:50" >> /etc/projid
[root@echidna ~]# xfs_quota -x
xfs_quota> path
      Filesystem          Pathname
 000  /quotatest/xfs      /dev/sda8 (uquota, pquota)
[001] /quotatest/xfs/proj-dir1 /dev/sda8 (project 50, dev-projects)
xfs_quota> project -s dev-projects
Setting up project dev-projects (path /quotatest/xfs/proj-dir1)...
Processed 1 (/etc/projects and cmdline) paths for project dev-projects with recursion
depth infinite (-1).
xfs_quota> limit -p bhard=15m dev-projects
xfs_quota> q

We'll illustrate the project quota in action by having user chris create some files. User chris is not a member of the development group and does not have any quotas set for either his id or group. Project quotas in action shows that chris cannot create more than 15MB of data in /quotatest/xfs/proj-dir1, but is not limited in /quotatest/xfs/proj-dir2.

Listing 19. Project quotas in action

[chris@echidna xfs]$ id chris
uid=1010(chris) gid=1010(chris) groups=1010(chris)
[chris@echidna xfs]$ dd if=/dev/zero of=proj-dir1/chris1 bs=1024 count=10000
10000+0 records in
10000+0 records out
10240000 bytes (10 MB) copied, 0.0379557 s, 270 MB/s
[chris@echidna xfs]$ cp proj-dir1/chris1 proj-dir1/chris2
cp: writing `proj-dir1/chris2': No space left on device
[chris@echidna xfs]$ ls -l proj-dir1
total 15356
-rw-rw-r--. 1 chris chris 10240000 Nov 23 13:16 chris1
-rw-rw-r--. 1 chris chris  5484544 Nov 23 13:16 chris2
[chris@echidna xfs]$ # Note: second copy was truncated at hard limit
[chris@echidna xfs]$ cp proj-dir1/chris1 proj-dir2/chris1
[chris@echidna xfs]$ cp proj-dir1/chris1 proj-dir2/chris2
[chris@echidna xfs]$ cp proj-dir1/chris1 proj-dir2/chris3
[chris@echidna xfs]$ du -sh *
15M     proj-dir1
30M     proj-dir2

Warning users

The warnquota command is used to send email warnings to users who are over quota. When a group is over quota, the email is sent to the user specified in /etc/quotagrpadmins for the group. The format of the email is controlled by the file /etc/warnquota.conf. The file /etc/quotatab is used to map names such as /dev/sda7 to more user-friendly descriptions such as "Shared EXT3 filesystem." Normally warnquota is run periodically as a cron job. See the man pages for cron and warnquota for more information.

This completes your introduction to quotas on Linux.