The `/usr/local/` Directory

The FHS says:

The /usr/local hierarchy is for use by the system administrator when installing software locally. It needs to be safe from being overwritten when the system software is updated. It may be used for programs and data that are shareable among a group of hosts, but not found in /usr.

The /usr/local/ directory is similar in structure to the /usr/ directory. It has the following subdirectories, which are similar in purpose to those in the /usr/ directory:

/usr/local
 |- bin/
 |- etc/
 |- games/
 |- include/
 |- lib/
 |- libexec/
 |- sbin/
 |- share/
 |- src/

In Community Enterprise Linux, the intended use for the /usr/local/ directory is slightly different from that specified by the FHS. The FHS says that /usr/local/ should be where software that is to remain safe from system software upgrades is stored. Since software upgrades can be performed safely with RPM Package Manager (RPM), it is not necessary to protect files by putting them in /usr/local/. Instead, the /usr/local/ directory is used for software that is 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/local/ directory.