18.15 File System Quotas

18.15.1 Configuring Your System to Enable Disk Quotas

Before attempting to use disk quotas, it is necessary to make sure that quotas are configured in your kernel. This is done by adding the following line to your kernel configuration file:

options QUOTA

The stock GENERIC kernel does not have this enabled by default, so you will have to configure, build and install a custom kernel in order to use disk quotas. Please refer to Κεφάλαιο 8 for more information on kernel configuration.

Next you will need to enable disk quotas in /etc/rc.conf. This is done by adding the line:

enable_quotas="YES"

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

check_quotas="NO"

Finally you will need to edit /etc/fstab to enable disk quotas on a per-file system basis. This is where you can either enable user or group quotas or both for all of your file systems.

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

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

Similarly, to enable group quotas, use the groupquota option instead of userquota. 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 with the names quota.user and quota.group for user and group quotas respectively. See fstab(5) for more information. Even though the fstab(5) manual page says that you can specify an alternate location for the quota files, this is not recommended because the various quota utilities do not seem to handle this properly.

At this point you should reboot your system with your new kernel. /etc/rc will automatically run the appropriate commands to create the initial quota files for all of the quotas you enabled in /etc/fstab, so there is no need to manually create any zero length quota files.

In the normal course of operations you should not be required to run the quotacheck(8), quotaon(8), or quotaoff(8) commands manually. However, you may want to read their manual pages just to be familiar with their operation.

18.15.2 Setting Quota Limits

Once you have configured your system to enable quotas, verify that they really are enabled. An easy way to do this is to run:

# quota -v

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

You are now ready to start assigning quota limits with the edquota(8) command.

You have several options on how to enforce limits on the amount of disk space a user or group may allocate, and how many files they may create. You may limit allocations based on disk space (block quotas) or number of files (inode quotas) or a combination of both. Each of these limits are further broken down into two categories: hard and soft limits.

A hard limit may not be exceeded. Once a user reaches his hard limit he may not make any further allocations on the file system in question. 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, on the other hand, can be exceeded for a limited amount of time. This period of time is known as the grace period, which is one week by default. If a user stays over his or her soft limit longer than the grace period, the soft limit will turn into a hard limit and no further allocations will be allowed. When the user drops back below the soft limit, the grace period will be reset.

The following is an example of what you might see when you run the edquota(8) command. When the edquota(8) command is invoked, you are placed into the editor specified by the EDITOR environment variable, or in the vi editor if the EDITOR variable is not set, to allow you to edit the quota limits.

# 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)

You will normally see two lines for each file system that has quotas enabled. One line for the block limits, and one line for inode limits. Simply change the value you want updated 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 will be in place when you exit the editor.

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

# edquota -p test 10000-19999

For more information see edquota(8) manual page.

18.15.3 Checking Quota Limits and Disk Usage

You can use either the quota(1) or the repquota(8) commands to check quota limits and disk usage. The quota(1) command can be used to check individual user or group quotas and disk usage. A user may only examine his own quota, and the quota of a group he is a member of. Only the super-user may view all user and group quotas. The repquota(8) command can be used to get a summary of all quotas and disk usage for file systems with quotas enabled.

The following is some sample output from the quota -v command 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

On the /usr file system in the above example, this user is currently 15 kbytes over the soft limit of 50 kbytes and has 5 days of the grace period left. Note the asterisk * which indicates that the user is currently over his quota limit.

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

18.15.4 Quotas over NFS

Quotas are enforced by the quota subsystem on the NFS server. The rpc.rquotad(8) daemon makes quota information available to the quota(1) command 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:

# kill -HUP `cat /var/run/inetd.pid`