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Chapter 36. Limiting storage space usage on ext4 with quotas

You have to enable disk quotas on your system before you can assign them. You can assign disk quotas per user, per group or per project. However, if there is a soft limit set, you can exceed these quotas for a configurable period of time, known as the grace period.

36.1. Installing the quota tool

You must install the quota RPM package to implement disk quotas.

Procedure

  • Install the quota package:

    # yum install quota

36.2. Enabling quota feature on file system creation

This procedure describes how to enable quotas on file system creation.

Procedure

  1. Enable quotas on file system creation:

    # mkfs.ext4 -O quota /dev/sda
    Note

    Only user and group quotas are enabled and initialized by default.

  2. Change the defaults on file system creation:

    # mkfs.ext4 -O quota -E quotatype=usrquota:grpquota:prjquota /dev/sda
  3. Mount the file system:

    # mount /dev/sda

Additional resources

  • ext4(5) man page.

36.3. Enabling quota feature on existing file systems

This procedure describes how to enable the quota feature on existing file system using the tune2fs command.

Procedure

  1. Unmount the file system:

    # umount /dev/sda
  2. Enable quotas on existing file system:

    # tune2fs -O quota /dev/sda
    Note

    Only user and group quotas are initialized by default.

  3. Change the defaults:

    # tune2fs -Q usrquota,grpquota,prjquota /dev/sda
  4. Mount the file system:

    # mount /dev/sda

Additional resources

  • ext4(5) man page.

36.4. Enabling quota enforcement

The quota accounting is enabled by default after mounting the file system without any additional options, but quota enforcement is not.

Prerequisites

  • Quota feature is enabled and the default quotas are initialized.

Procedure

  • Enable quota enforcement by quotaon for the user quota:

    # mount /dev/sda /mnt
    # quotaon /mnt
    Note

    The quota enforcement can be enabled at mount time using usrquota, grpquota, or prjquota mount options.

    # mount -o usrquota,grpquota,prjquota /dev/sda /mnt
  • Enable user, group, and project quotas for all file systems:

    # quotaon -vaugP
    • If neither of the -u, -g, or -P options are specified, only the user quotas are enabled.
    • If only -g option is specified, only group quotas are enabled.
    • If only -P option is specified, only project quotas are enabled.
  • Enable quotas for a specific file system, such as /home:

    # quotaon -vugP /home

Additional resources

  • quotaon(8) man page.

36.5. Assigning quotas per user

The disk quotas are assigned to users with the edquota command.

Note

The text editor defined by the EDITOR environment variable is used by edquota. To change the editor, set the EDITOR environment variable in your ~/.bash_profile file to the full path of the editor of your choice.

Prerequisites

  • User must exist prior to setting the user quota.

Procedure

  1. Assign the quota for a user:

    # edquota username

    Replace username with the user to which you want to assign the quotas.

    For example, if you enable a quota for the /dev/sda partition and execute the command edquota testuser, the following is displayed in the default editor configured on the system:

    Disk quotas for user testuser (uid 501):
    Filesystem   blocks   soft   hard   inodes   soft   hard
    /dev/sda      44043      0      0    37418      0      0
  2. Change the desired limits.

    If any of the values are set to 0, limit is not set. Change them in the text editor.

    For example, the following shows the soft and hard block limits for the testuser have been set to 50000 and 55000 respectively.

    Disk quotas for user testuser (uid 501):
    Filesystem   blocks   soft   hard   inodes   soft   hard
    /dev/sda      44043  50000  55000    37418      0      0
    • The first column is the name of the file system that has a quota enabled for it.
    • The second column shows how many blocks the user is currently using.
    • The next two columns are used to set soft and hard block limits for the user on the file system.
    • The inodes column shows how many inodes the user is currently using.
    • The last two columns are used to set the soft and hard inode limits for the user on the file system.

      • The hard block limit is the absolute maximum amount of disk space that a user or group can use. Once this limit is reached, no further disk space can be used.
      • The soft block limit defines the maximum amount of disk space that can be used. However, unlike the hard limit, the soft limit can be exceeded for a certain amount of time. That time is known as the grace period. The grace period can be expressed in seconds, minutes, hours, days, weeks, or months.

Verification steps

  • Verify that the quota for the user has been set:

    # quota -v testuser
    Disk quotas for user testuser:
    Filesystem  blocks  quota  limit  grace  files  quota  limit  grace
    /dev/sda      1000*  1000   1000             0      0      0

36.6. Assigning quotas per group

You can assign quotas on a per-group basis.

Prerequisites

  • Group must exist prior to setting the group quota.

Procedure

  1. Set a group quota:

    # edquota -g groupname

    For example, to set a group quota for the devel group:

    # edquota -g devel

    This command displays the existing quota for the group in the text editor:

    Disk quotas for group devel (gid 505):
    Filesystem   blocks  soft  hard  inodes  soft  hard
    /dev/sda     440400     0     0   37418     0     0
  2. Modify the limits and save the file.

Verification steps

  • Verify that the group quota is set:

    # quota -vg groupname

36.7. Assigning quotas per project

This procedure assigns quotas per project.

Prerequisites

  • Project quota is enabled on your file system.

Procedure

  1. Add the project-controlled directories to /etc/projects. For example, the following adds the /var/log path with a unique ID of 11 to /etc/projects. Your project ID can be any numerical value mapped to your project.

    # echo 11:/var/log >> /etc/projects
  2. Add project names to /etc/projid to map project IDs to project names. For example, the following associates a project called Logs with the project ID of 11 as defined in the previous step.

    # echo Logs:11 >> /etc/projid
  3. Set the desired limits:

    # edquota -P 11
    Note

    You can choose the project either by its project ID (11 in this case), or by its name (Logs in this case).

  4. Using quotaon, enable quota enforcement:

    See Enabling quota enforcement.

Verification steps

  • Verify that the project quota is set:

    # quota -vP 11
    Note

    You can verify either by the project ID, or by the project name.

Additional resources

  • edquota(8) man page.
  • projid(5) man page.
  • projects(5) man page.

36.8. Setting the grace period for soft limits

If a given quota has soft limits, you can edit the grace period, which is the amount of time for which a soft limit can be exceeded. You can set the grace period for users, groups, or projects.

Procedure

  • Edit the grace period:

    # edquota -t
Important

While other edquota commands operate on quotas for a particular user, group, or project, the -t option operates on every file system with quotas enabled.

Additional resources

  • edquota(8) man page.

36.9. Turning file system quotas off

Use quotaoff to turn disk quota enforcement off on the specified file systems. Quota accounting stays enabled after executing this command.

Procedure

  • To turn all user and group quotas off:

    # quotaoff -vaugP
    • If neither of the -u, -g, or -P options are specified, only the user quotas are disabled.
    • If only -g option is specified, only group quotas are disabled.
    • If only -P option is specified, only project quotas are disabled.
    • The -v switch causes verbose status information to display as the command executes.

Additional resources

  • quotaoff(8) man page.

36.10. Reporting on disk quotas

You can create a disk quota report using the repquota utility.

Procedure

  1. Run the repquota command:

    # repquota

    For example, the command repquota /dev/sda produces this output:

    *** Report for user quotas on device /dev/sda
    Block grace time: 7days; Inode grace time: 7days
    			Block limits			File limits
    User		used	soft	hard	grace	used	soft	hard	grace
    ----------------------------------------------------------------------
    root      --      36       0       0              4     0     0
    kristin   --     540       0       0            125     0     0
    testuser  --  440400  500000  550000          37418     0     0
  2. View the disk usage report for all quota-enabled file systems:

    # repquota -augP

The -- symbol displayed after each user determines whether the block or inode limits have been exceeded. If either soft limit is exceeded, a + character appears in place of the corresponding - character. The first - character represents the block limit, and the second represents the inode limit.

The grace columns are normally blank. If a soft limit has been exceeded, the column contains a time specification equal to the amount of time remaining on the grace period. If the grace period has expired, none appears in its place.

Additional resources

The repquota(8) man page for more information.