9.2. Managing Disk Quotas

If quotas are implemented, they need some maintenance — mostly in the form of watching to see if the quotas are exceeded and making sure the quotas are accurate.
Of course, if users repeatedly exceed their quotas or consistently reach their soft limits, a system administrator has a few choices to make depending on what type of users they are and how much disk space impacts their work. The administrator can either help the user determine how to use less disk space or increase the user's disk quota.

9.2.1. Enabling and Disabling

It is possible to disable quotas without setting them to 0. To turn all user and group quotas off, use the following command: 
quotaoff -vaug
If neither the -u or -g options are specified, only the user quotas are disabled. If only -g is specified, only group quotas are disabled. The -v switch causes verbose status information to display as the command executes.
To enable quotas again, use the quotaon command with the same options.
For example, to enable user and group quotas for all file systems, use the following command: 
quotaon -vaug
To enable quotas for a specific file system, such as /home, use the following command: 
quotaon -vug /home
If neither the -u or -g options are specified, only the user quotas are enabled. If only -g is specified, only group quotas are enabled.

9.2.2. Reporting on Disk Quotas

Creating a disk usage report entails running the repquota utility. For example, the command repquota /home produces this output: 
*** Report for user quotas on device /dev/mapper/VolGroup00-LogVol02
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
To view the disk usage report for all (option -a) quota-enabled file systems, use the command: 
repquota -a
While the report is easy to read, a few points should be explained. The -- displayed after each user is a quick way to determine whether the block or inode limits have been exceeded. If either soft limit is exceeded, a + appears in place of the corresponding -; the first - 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.

9.2.3. Keeping Quotas Accurate

Whenever a file system is not unmounted cleanly (due to a system crash, for example), it is necessary to run quotacheck. However, quotacheck can be run on a regular basis, even if the system has not crashed. Safe methods for periodically running quotacheck include:
Ensuring quotacheck runs on next reboot

Note

This method works best for (busy) multiuser systems which are periodically rebooted.
As root, place a shell script into the /etc/cron.daily/ or /etc/cron.weekly/ directory—or schedule one using the crontab -e command—that contains the touch /forcequotacheck command. This creates an empty forcequotacheck file in the root directory, which the system init script looks for at boot time. If it is found, the init script runs quotacheck. Afterward, the init script removes the /forcequotacheck file; thus, scheduling this file to be created periodically with cron ensures that quotacheck is run during the next reboot.
Refer to Chapter 39, Automated Tasks for more information about configuring cron.
Running quotacheck in single user mode
An alternative way to safely run quotacheck is to (re-)boot the system into single-user mode to prevent the possibility of data corruption in quota files and run: 
~]# quotaoff -vaug /<file_system>
~]# quotacheck -vaug /<file_system>
~]# quotaon -vaug /<file_system>
Running quotacheck on a running system
If necessary, it is possible to run quotacheck on a machine during a time when no users are logged in, and thus have no open files on the file system being checked. Run the command quotacheck -vaug <file_system> ; this command will fail if quotacheck cannot remount the given <file_system> as read-only. Note that, following the check, the file system will be remounted read-write.

Important

Running quotacheck on a live file system mounted read-write is not recommended due to the possibility of quota file corruption.
Refer to Chapter 39, Automated Tasks for more information about configuring cron.