Disk quota

From Wikipedia:

"A disk quota is a limit set by a system administrator that restricts certain aspects of file system usage on modern operating systems. The function of setting quotas to disks is to allocate limited disk-space in a reasonable way."

This article covers the installation and setup of disk quota.

Installing

Disk quota only requires one package:

# pacman -S quota-tools

Enabling

For journaled quota, see the notes in #Journaled quota.

1. First, edit /etc/fstab to enable the quota mount option(s) on selected file systems:

 /dev/sda1 /home ext4 defaults 1 1

edit it as follows;

 /dev/sda1 /home ext4 defaults,usrquota 1 1

or aditionally enable the group quota mount option;

 /dev/sda1 /home ext4 defaults,usrquota,grpquota 1 1

2. Create the quota files in the file system:

 # touch /home/aquota.user
 # touch /home/aquota.group     # For group quota

2. The next step is to remount:

 # mount -vo remount /home

4. Create the quota index:

 # quotacheck -vgum /home

or for all partitions with the quota mount options in /etc/mtab;

 # quotacheck -vguma

Tip: If you end up with the output "[...]Quotafile $FILE was probably truncated. Cannot save quota settings..." you can try removing the previously created files aquota*

Tip: If you get the output "quotacheck: Mountpoint (or device) /home not found or has no quota enabled.
quotacheck: Cannot find filesystem to check or filesystem not mounted with quota option." and you are using a custom kernel, make sure quota support is enabled in your kernel.

Tip: In Addition you can try to use "-F vfsold" and "-F vfsv0" afterwards NOTE: As of 3.1.6-1, Arch does not support "vfsv1"

5. Finally, enable quotas:

 # quotaon -av

Tip: to automatically enable quota on boot, add quotaon -a >/dev/null 2>&1 to /etc/rc.local.

Journaled quota

Enabling journaling for disk quota adds the same benefits journaled file systems do for forced shutdowns, meaning that data is less likely to become corrupt.

Setting up journaled quota is the same as above, except for the mount options:

/dev/sda1 /home ext4 defaults,usrjquota=aquota.user,jqfmt=vfsv0 1 1

or aditionally enable the group quota mount option;

/dev/sda1 /home ext4 defaults,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0 1 1

Configuring

Replace $USER as appropriate and edit the quota as root:

$ edquota $USER

Disk quotas for user $USER (uid 1000):
  Filesystem                   blocks       soft       hard     inodes     soft     hard
  /dev/sda1                      1944          0          0        120        0        0

Note: to edit group quotas, use edquota -g $GROUP.

blocks

Number of 1k blocks currently used by $USER

inodes

Number of entries by $USER in directory file

soft

Max number of blocks/inodes $USER may have on partition before warning is issued and grace period countdown begins. If set to "0" (zero) then no limit is enforced.

hard

Max number of blocks/inodes $USER may have on partition. If set to "0" (zero) then no limit is enforced.

Example configuration:

Disk quotas for user testuser (uid 1000):
Filesystem      blocks       soft       hard     inodes     soft   hard       
/dev/sda1       695879       10000      15000     6741        0      0

The soft limit means that once testuser uses over 10MB of space a warning email gets ensued, and after a period of time the soft limit gets enforced.

The hard limit is stricter, so to speak; a user cannot go over this limit.

Next configure the soft limit grace period:

# edquota -t

Managing

Checking for quota limits and advanced operations

Basics

Use this command to check for quotas on a specific partition:

# repquota /home

Use this command to check for all quotas that apply to a user:

# quota -u $USER

for groups;

# quota -g $GROUP

Copying quota settings

To copy quota from one user or group to the other, use this command:

# edquota -p user1 user2

User1 is the user you copy from, user2 is the user you copy quota to. Of course you can replace user with group, when necessary.

Multiple users

The idea is to make a temporary user acount, modify the quota settings for that user, and then copy the generated quota files for all users to use. After setting quota settings for quotauser, copy the settings:

# edquota -p quotauser `awk -F: '$3 > 999 {print $1}' /etc/passwd`

This applies the settings to users with a UID equal to or greater than 1000.

Other commands

There are several useful commands:

repquota -a      # Shows the status on disk usage
warnquota        # Can be used to warn the users about their quota
setquota         # Non-interactive quota setting--useful for scripting

Lasty, quotastats is used to give thorough information about the quota system:

$ quotastats

Number of dquot lookups: 101289
Number of dquot drops: 101271
Number of still active inodes with quota : 18
Number of dquot reads: 93
Number of dquot writes: 2077
Number of quotafile syncs: 134518740
Number of dquot cache hits: 7391
Number of allocated dquots: 90
Number of free dquots: 2036
Number of in use dquot entries (user/group): -1946

More resources

• http://tldp.org/HOWTO/Quota.html
• http://www.sf.net/projects/linuxquota/
• http://www.yolinux.com/TUTORIALS/LinuxTutorialQuotas.html
• http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/admin-primer/s1-storage-quotas.html