System information

/usr/src
This directory stores source code.
/usr/tmp lin ked t o /var/tmp
This directory stores temporary files.
The /usr/ directory should also contain a /l o cal / subdirectory. As per the FHS, this subdirectory
is used by the system administrator when installing software locally, and should be safe from being
overwritten during system updates. The /usr/l o cal directory has a structure similar to /usr/, and
contains the following subdirectories:
/usr/l o cal /bi n
/usr/l o cal /etc
/usr/l o cal /g ames
/usr/l o cal /i ncl ud e
/usr/l o cal /l i b
/usr/l o cal /l i bexec
/usr/l o cal /sbi n
/usr/l o cal /share
/usr/l o cal /src
Red Hat Enterprise Linux's usage of /usr/l o cal / differs slightly from the FHS. The FHS states that
/usr/l o cal / should be used to store software that should remain safe from system software
upgrades. Since the RPM Packag e Man ag er can perform software upgrades safely, it is not
necessary to protect files by storing them in /usr/l o cal /.
Instead, Red Hat Enterprise Linux uses /usr/l o cal / for software local to the machine. For
instance, if the /usr/ directory is mounted as a read-only NFS share from a remote host, it is still
possible to install a package or program under the /usr/l o cal / directory.
2.1 .1 .1 4 . T he /var/ Direct o ry
Since the FHS requires Linux to mount /usr/ as read-only, any programs that write log files or need
spo o l / or l o ck/ directories should write them to the /var/ directory. The FHS states /var/ is for
variable data, which includes spool directories and files, logging data, transient and temporary files.
Below are some of the directories found within the /var/ directory depending on what is installed on
the system:
/var/acco unt/
/var/arpwatch/
/var/cache/
/var/crash/
/var/d b/
/var/empty/
⁠Chapt er 2 . File Syst em St ruct ure and Maint enance
21