Managing filesystem types

Quotas on the ufs filesystem

The quota system (available only on ufs and vxfs filesystems) is built around limits on the two principal resources of a filesystem:

inodes
data blocks

For each of these resources, users can be assigned quotas. A quota in this case consists of two limits, known as the soft and hard limits.

The hard limit represents an absolute limit on the resource, blocks or inodes, that the user can never exceed under any circumstances.

Associated with the soft limit is a time limit set by the administrator. Users can exceed the soft limits assigned to them, but only for a limited amount of time--the time limit set by the administrator. This allows users to temporarily exceed limits if needed, as long as they are back under those limits before the time limit expires. An example of such a situation might be the generation of a large file that is printed and then deleted.

In summary, for each user, you can assign quotas (soft and hard limits) for both blocks and inodes. You can also define a time limit that applies to all users on a filesystem indicating how long they can exceed the soft limits. There are actually two time limits: one for blocks and one for inodes. You can define different time limits for different filesystems.

Using quotas

Before turning quotas on for a filesystem for the first time, do the following:

Mount the filesystem and change directory to the mount point.
Create a file called quotas, owned by root; others should not be able to write to it.
To change the time limits for exceeding the soft limits for blocks owned and/or inodes owned, enter:
```
   edquota -t
```
These limits are initially set to the values defined for DQ_FTIMELIMIT and DQ_BTIMELIMIT in /usr/include/sys/fs/sfs_quota.h--604800 (the number of seconds in one week). If you leave either time limit (the one for exceeding the block limit or the one for exceeding the inode limit) at 0, or if you set either limit to 0, the default values apply. You can change them to something else.
To set user quotas, enter:
```
   edquota
```
See edquota(1M) for details on its use.
Once you have set the quotas for a user, you can use the -p option to set the same quotas for another user. Because you are not limited to UIDs that are already being used, you can set quotas for future users.

NOTE: Before turning on quotas on a filesystem, always run quotacheck(1M) on the filesystem. This will sync up the quotas with the actual state of the filesystem, so that if the filesystem has been used since the last time the quotas were turned on, all of the quotas will be updated to reflect the current state. This also provides a sanity check on the quotas file.

You can also do other quota-related functions:

To turn quotas on, enter:
```
   quotaon
```
To turn quotas off, enter:
```
   quotaoff
```
To report on quotas, enter:
```
   repquota
```
To get information on all users on a filesystem, enter:
```
   quot
```
To get information on a single user, enter:
```
   quota
```

NOTE: Regular users can use quota to get information on their own quotas; they cannot get information on other user's quotas.

What effect do quotas have on the user?

The following are the major effects of the use of quotas on users:

If a user exceeds the soft limit for blocks or inodes, the timer is started. If the user then reduces usage to a level under the soft limit, the timer is turned off and all is well. But if the user still has not reduced usage to an appropriate level when the timer expires, any further attempts by the user to acquire more filesystem resources fail and the user receives error messages saying that the filesystem is full. These messages persist until the user has reduced usage to a level below the soft limit.
If a user tries to exceed the hard limit at any time, the attempt fails and the utility indicates it has run out of space.
Because no warning is given when the user has exceeded the soft limit, advise users to run quota frequently. Encourage users to include quota in their .profile so it runs when they log in.