19.13. File System Quotas

Quotas are an optional feature of the operating system that can be used to limit the amount of disk space or the number of files a user or members of a group may allocate on a per-file system basis. This is used most often on timesharing systems where it is desirable to limit the amount of resources any one user or group of users may allocate. This prevents one user or group of users from consuming all of the available disk space.

19.13.1. Configuring the System to Enable Disk Quotas

Before using disk quotas, quota support must be added to the kernel by adding the following line to the kernel configuration file:

options QUOTA

Before FreeBSD 9.2, the GENERIC kernel usually did not include this option. sysctl kern.features.ufs_quota can be used to test whether the current kernel supports quotas. If the option is not present, a custom kernel must be compiled. Refer to Κεφάλαιο 9, Ρυθμίζοντας τον Πυρήνα του FreeBSD for more information on kernel configuration.

Next, enable disk quotas in /etc/rc.conf:

quota_enable="YES"

For finer control over quota startup, an additional configuration variable is available. Normally on bootup, the quota integrity of each file system is checked by quotacheck(8). This program insures that the data in the quota database properly reflects the data on the file system. This is a time consuming process that will significantly affect the time the system takes to boot. To skip this step, add this variable to /etc/rc.conf:

check_quotas="NO"

Finally, edit /etc/fstab to enable disk quotas on a per-file system basis. This is when user or group quotas can be enabled on the file systems.

To enable per-user quotas on a file system, add userquota to the options field in the /etc/fstab entry for the file system to enable quotas on. For example:

/dev/da1s2g   /home    ufs rw,userquota 1 2

To enable group quotas, instead use groupquota. To enable both user and group quotas, change the entry as follows:

/dev/da1s2g    /home    ufs rw,userquota,groupquota 1 2

By default, the quota files are stored in the root directory of the file system as quota.user and quota.group. Refer to fstab(5) for more information. Even though an alternate location for the quota files can be specified, this is not recommended because the various quota utilities do not seem to handle this properly.

Once the configuration is complete, reboot the system with the new kernel. /etc/rc will automatically run the appropriate commands to create the initial quota files for all of the quotas enabled in /etc/fstab. There is no need to manually create any zero length quota files.

In the normal course of operations, there should be no need to manually run quotacheck(8), quotaon(8), or quotaoff(8). However, one should read their manual pages to be familiar with their operation.

19.13.2. Setting Quota Limits

Once the system has been configured to enable quotas, verify they really are enabled by running:

# quota -v

There should be a one line summary of disk usage and current quota limits for each file system that quotas are enabled on.

The system is now ready to be assigned quota limits with edquota(8).

Several options are available to enforce limits on the amount of disk space a user or group may allocate, and how many files they may create. Allocations can be limited based on disk space (block quotas), number of files (inode quotas), or a combination of both. Each limits is further broken down into two categories: hard and soft limits.

A hard limit may not be exceeded. Once a user reaches a hard limit, no further allocations can be made on that file system by that user. For example, if the user has a hard limit of 500 kbytes on a file system and is currently using 490 kbytes, the user can only allocate an additional 10 kbytes. Attempting to allocate an additional 11 kbytes will fail.

Soft limits can be exceeded for a limited amount of time, known as the grace period, which is one week by default. If a user stays over their limit longer than the grace period, the soft limit turns into a hard limit and no further allocations are allowed. When the user drops back below the soft limit, the grace period is reset.

The following is an example output from edquota(8). When edquota(8) is invoked, the editor specified by EDITOR is opened in order to edit the quota limits. The default editor is set to vi.

# edquota -u test
Quotas for user test:
/usr: kbytes in use: 65, limits (soft = 50, hard = 75)
        inodes in use: 7, limits (soft = 50, hard = 60)
/usr/var: kbytes in use: 0, limits (soft = 50, hard = 75)
        inodes in use: 0, limits (soft = 50, hard = 60)

There are normally two lines for each file system that has quotas enabled. One line represents the block limits and the other represents the inode limits. Change the value to modify the quota limit. For example, to raise this user's block limit from a soft limit of 50 and a hard limit of 75 to a soft limit of 500 and a hard limit of 600, change:

/usr: kbytes in use: 65, limits (soft = 50, hard = 75)

to:

/usr: kbytes in use: 65, limits (soft = 500, hard = 600)

The new quota limits take affect upon exiting the editor.

Sometimes it is desirable to set quota limits on a range of UIDs. This can be done by passing -p to edquota(8). First, assign the desired quota limit to a user, then run edquota -p protouser startuid-enduid. For example, if test has the desired quota limits, the following command will duplicate those quota limits for UIDs 10,000 through 19,999:

# edquota -p test 10000-19999

For more information, refer to edquota(8).

19.13.3. Checking Quota Limits and Disk Usage

Either quota(1) or repquota(8) can be used to check quota limits and disk usage. To check individual user or group quotas and disk usage, use quota(1). A user may only examine their own quota and the quota of a group they are a member of. Only the superuser may view all user and group quotas. To get a summary of all quotas and disk usage for file systems with quotas enabled, use repquota(8).

The following is sample output from quota -v for a user that has quota limits on two file systems.

Disk quotas for user test (uid 1002):
     Filesystem  usage    quota   limit   grace   files   quota   limit   grace
           /usr      65*     50      75   5days       7      50      60
       /usr/var       0      50      75               0      50      60

In this example, the user is currently 15 kbytes over the soft limit of 50 kbytes on /usr and has 5 days of grace period left. The asterisk * indicates that the user is currently over the quota limit.

Normally, file systems that the user is not using any disk space on will not show in the output of quota(1), even if the user has a quota limit assigned for that file system. Use -v to display those file systems, such as /usr/var in the above example.

19.13.4. Quotas over NFS

Quotas are enforced by the quota subsystem on the NFS server. The rpc.rquotad(8) daemon makes quota information available to quota(1) on NFS clients, allowing users on those machines to see their quota statistics.

Enable rpc.rquotad in /etc/inetd.conf like so:

rquotad/1      dgram rpc/udp wait root /usr/libexec/rpc.rquotad rpc.rquotad

Now restart inetd:

# service inetd restart

Αυτό το κείμενο, και άλλα κείμενα, μπορεί να βρεθεί στο ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/

Για ερωτήσεις σχετικά με το FreeBSD, διαβάστε την τεκμηρίωση πριν να επικοινωνήσετε με την <questions@FreeBSD.org>.

Για ερωτήσεις σχετικά με αυτή την τεκμηρίωση, στείλτε e-mail στην <doc@FreeBSD.org>.