What Are Quotas

Quotas enable system administrators to control the size of UFS file systems by limiting the amount of disk space and the number of inodes (which roughly corresponds to the number of files) that individual users can acquire. For this reason, quotas are especially useful on the file systems where user home directories reside. (As a rule, public and /tmp file systems probably wouldn't benefit as much from the establishment of quotas.)

Setting up quotas involves these general steps:

1. A series of commands prepares a file system to accept quotas, ensuring that quotas will be enforced each time the system is rebooted and the file system is mounted. Entries must be added to the /etc/vfstab file, and a quotas file must be created in the top-level directory of the file system.

2. After a quota is created for one user, it can be copied as a prototype to set up other user quotas.

3. Before quotas are actually turned on, another command checks for consistency by comparing the proposed quotas to the current disk usage making sure there are no conflicts.

4. Finally, a command turns the quotas on for one or more entire file systems.

These steps ensure that quotas are automatically activated on a file system each time it is mounted. See Chapter 58, Managing Quotas (Tasks) for specific information about these procedures.

Once they are in place, quotas can be changed to adjust the amount of disk space or number of inodes that users can consume. Additionally, quotas can be added or removed as system needs change. See "Changing and Removing Quotas" for instructions on how to change quotas, disable individual quotas, or remove quotas from file systems.

In addition, quota status can be monitored. Quota commands enable administrators to display information about quotas on a file system, or search for users who have exceeded their quotas. For procedures that describe how to use these commands, see "Checking Quotas".