The use of disk quotas allows system administrators to effectively manage disk space shared by multiple users. Quota systems are implemented on Microsoft Windows NT and its derivatives (but only on NTFS-formatted volumes), Unix-like operating systems, and Novell Netware, amongst others.
Quotas restrict the ability of users to access file system resources, such as blocks (allocation units) and inodes (file system entries). Once a user has exceeded their quota limit, a new policy takes effect describing the range of the user's behavoir. Quota limits are administered on individual file systems and are unique to users or groups. Users who can write to more than one file system must have an entry on each. Various tools are available for administrating and automating quota policies on a system.
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