Chapter 13. Implementing Disk Quotas
Disk space can be restricted by implementing disk quotas which alert a system administrator before a user consumes too much disk space or a partition becomes full.
Disk quotas can be configured for individual users as well as user groups. This kind of flexibility makes it possible to give each user a small quota to handle "personal" files (such as email and reports), while allowing the projects they work on to have more sizable quotas (assuming the projects are given their own groups).
In addition, quotas can be set not just to control the number of disk blocks consumed but to control the number of inodes (data structures that contain information about files in UNIX file systems). Because inodes are used to contain file-related information, this allows control over the number of files that can be created.
quotaRPM must be installed to implement disk quotas.
13.1. Configuring Disk Quotas
To implement disk quotas, use the following steps:
- Enable quotas per file system by modifying the
- Remount the file system(s).
- Create the quota database files and generate the disk usage table.
- Assign quota policies.
Each of these steps is discussed in detail in the following sections.
13.1.1. Enabling Quotas
As root, using a text editor, edit the
/etc/fstabfile. Add the
grpquotaoptions to the file systems that require quotas:
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1 LABEL=/boot /boot ext3 defaults 1 2 none /dev/pts devpts gid=5,mode=620 0 0 none /dev/shm tmpfs defaults 0 0 none /proc proc defaults 0 0 none /sys sysfs defaults 0 0 /dev/VolGroup00/LogVol02 /home ext3 defaults,usrquota,grpquota 1 2 /dev/VolGroup00/LogVol01 swap swap defaults 0 0 . . .
In this example, the
/homefile system has both user and group quotas enabled.
The following examples assume that a separate
/homepartition was created during the installation of Red Hat Enterprise Linux. Although not ideal, the root (
/) partition (the installation default created partition) can be used for setting quota policies in the
13.1.2. Remounting the File Systems
After adding the
grpquotaoptions, remount each file system whose
fstabentry has been modified. If the file system is not in use by any process, use one of the following methods:
- Issue the
umountcommand followed by the
mountcommand to remount the file system.
- Issue the
mount -o remount /homecommand to remount the file system.
If the file system is currently in use, the easiest method for remounting the file system is to reboot the system.
13.1.3. Creating the Quota Database Files
After each quota-enabled file system is remounted, the system is capable of working with disk quotas. However, the file system itself is not yet ready to support quotas. The next step is to run the
quotacheckcommand examines quota-enabled file systems and builds a table of the current disk usage per file system. The table is then used to update the operating system's copy of disk usage. In addition, the file system's disk quota files are updated.
To create the quota files (
aquota.group) on the file system, use the
-coption of the
quotacheckcommand. For example, if user and group quotas are enabled for the
/homefile system, create the files in the
quotacheck -cug /home
-coption specifies that the quota files should be created for each file system with quotas enabled, the
-uoption specifies to check for user quotas, and the
-goption specifies to check for group quotas.
If neither the
-goptions are specified, only the user quota file is created. If only
-gis specified, only the group quota file is created.
After the files are created, run the following command to generate the table of current disk usage per file system with quotas enabled:
The options used are as follows:
a— Check all quota-enabled, locally-mounted file systems
v— Display verbose status information as the quota check proceeds
u— Check user disk quota information
g— Check group disk quota information
quotacheckhas finished running, the quota files corresponding to the enabled quotas (user and/or group) are populated with data for each quota-enabled locally-mounted file system such as
13.1.4. Assigning Quotas per User
The last step is assigning the disk quotas with the
To configure the quota for a user, as root in a shell prompt, execute the command:
Perform this step for each user who needs a quota. For example, if a quota is enabled in
/dev/VolGroup00/LogVol02) and the command
edquota testuseris executed, the following is shown in the editor configured as the default for the system:
Disk quotas for user testuser (uid 501): Filesystem blocks soft hard inodes soft hard /dev/VolGroup00/LogVol02 440436 0 0 37418 0 0
The text editor defined by the
EDITORenvironment variable is used by
edquota. To change the editor, set the
EDITORenvironment variable in your
~/.bash_profilefile to the full path of the editor of your choice.
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
inodescolumn 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.
A hard 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 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.
If any of the values are set to 0, that limit is not set. In the text editor, change the desired limits. For example:
Disk quotas for user testuser (uid 501): Filesystem blocks soft hard inodes soft hard /dev/VolGroup00/LogVol02 440436 500000 550000 37418 0 0
To verify that the quota for the user has been set, use the command:
13.1.5. Assigning Quotas per Group
Quotas can also be assigned on a per-group basis. For example, to set a group quota for the
develgroup (the group must exist prior to setting the group quota), use the command:
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/VolGroup00/LogVol02 440400 0 0 37418 0 0
Modify the limits, save the file, and then configure the quota.
To verify that the group quota has been set, use the command:
quota -g devel
13.1.6. Assigning Quotas per File System
To assign quotas based on each file system enabled for quotas, use the command:
Like the other
edquotacommands, this one opens the current quotas for the file system in the text editor:
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/mapper/VolGroup00-LogVol02 7days 7days
Change the block grace period or inode grace period, save the changes to the file, and exit the text editor.