"SYSTEM ADMINISTRATORS ROUTINELY "CLEAN" their file systems by
removing unused files and organizing files into directories. The
term "clean" is also associated with performing file system checks
to ensure structural integrity with tools such as fsck.ext3(8). In
addition to these critical activities, you should routinely "clean"
file system access controls — ownerships and permissions.
"Unowned Files and Directories
"An unowned file or directory is one in which no owner or group
has been assigned. All accounts and group have a numerical
identifier associated with them — referred to as the user
identifier (uid) and group identifier (gid).
"For example, I have an account called darth (uid=502) and it
belongs to two groups: darth (gid=502) and vader (gid=503). I
created the file /tmp/deathstar which is owned by darth and
assigned group vader:"