User. The "/
usr" directory hierarchy on
Unix systems. Once
upon a time, in the early days of Unix, this area actually
held users' home directories and files. Since these tend to
expand much faster than system files, /
usr would be mounted on
the biggest disk on the system. The root directory, "/" in
contrast, contains only what is needed to
boot the
kernel,
after which /
usr and other disks could be mounted as part of
the multi-user start-up process.
/
usr has been used as the "everything else" area, with many
"system" files such as compiler libraries (/
usr/include,
/
usr/lib), utilty programs (/
usr/bin, /
usr/ucb), games
(/
usr/games), local additions (/
usr/local), manuals
(/
usr/man), temporary files and queues for various
daemons
(/
usr/spool). These optional extras have grown in size as
Unix has evolved and disks have dropped in price. Under later
versions of
SunOS, the user files have fled /
usr altogether
for a new "/home"
partition and temporary files have moved
to "/var". This allows /
usr to be mounted read-only with some
gain in security and performance since access times are not
updated for files on read-only file systems.