What Are Quotas?

Quotas are a way of controlling the amount of space that a user, or a number of users, is allowed to utilize on the system. By setting limits for users, quotas force users to clean up and generally maintain their allocated directories.

Quotas are normally only used on systems where disk space is critical. They are set on a per-filesystem basis and control both disk space and the number of files. Users are allowed a soft limit and a hard limit for both the amount of disk space they can use and the number of files they can create. They may use up to their soft limit without any problems; in fact, they can even exceed it for a predefined time period—a soft limit is there to provide a buffer for the user. The hard limit is a finite limit—users cannot use more than this value.

Users are notified if their soft limit is exceeded. From here, they must tidy up their files. Otherwise, if the usage still exceeds the soft limit, when the time period expires it becomes a hard limit and is enforced as such.