User and Group Quotas

Although there may be multiple users of a filesystem, it is possible for a single user to consume all of the space within the filesystem. User and group quotas provide the mechanisms by which the amount of space used by a single user or all users within a specific group can be limited to a value defined by the administrator.

Quotas are based on the number of files used and the number of blocks. Some filesystems have a limited number of inodes available. Even though the amount of space consumed by a user may be small, it is still possible to consume all of the files in the filesystem even though most of the free space is still available.

Quotas operate around two limits that allow the user to take some action if the amount of space or number of disk blocks start to exceed the administrator defined limits:

Soft Limit. If the user exceeds the limit defined, there is a grace period that allows the user to free up some space. The quota can be exceeded during this time. However, after the time period has expired, no more files or data blocks may be allocated.

Hard Limit. When the hard limit is reached, regardless of the grace period, no further files or blocks can be allocated.

The grace period is set on a per-filesystem basis. For the VxFS filesystem, the default is seven days. The soft limit allows for users running applications that may create a lot of temporary files that only exist for the duration of the application. If the soft limit is exceeded, no action ...

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