Filesystem, Missing Space

A portion of each UFS partition (8%, by default) is reserved for use by the operating system and the root user. This helps keep the system from immediately crashing when users fill up important partitions, and ensures that the system administrator will be able to buy himself/herself some immediate time to secure more storage space before serious problems occur - the users will see "filesystem full" once the 92% limit is reached, but root processes continue working fine, and the admin can immediately "fix" the problem afterwards on a temporary basis simply by removing the 92% cap until s/he has secured and attached more storage space.

(See also: tunefs)