/usr/lib<qual> : Alternate format libraries (optional)
Purpose
/usr/lib<qual> performs the same role as /usr/lib for an alternate binary format, except that the symbolic links /usr/lib<qual>/sendmail and /usr/lib<qual>/X11 are not required. [26]
/usr/local : Local hierarchy
Purpose
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 amongst a group of hosts, but not found in /usr.
Locally installed software must be placed within /usr/local rather than /usr unless it is being installed to replace or upgrade software in /usr. [27]
Requirements
The following directories, or symbolic links to directories, must be in /usr/local
| Directory | Description |
|---|---|
| bin | Local binaries |
| etc | Host-specific system configuration for local binaries |
| games | Local game binaries |
| include | Local C header files |
| lib | Local libraries |
| man | Local online manuals |
| sbin | Local system binaries |
| share | Local architecture-independent hierarchy |
| src | Local source code |
No other directories, except those listed below, may be in /usr/local after first installing a FHS-compliant system.
Specific Options
If directories /lib<qual> or /usr/lib<qual> exist, the equivalent directories must also exist in /usr/local.
/usr/local/etc may be a symbolic link to /etc/local.
The consistency of /usr/local/etc is beneficial to installers, and is already used in other systems. As all of /usr/local needs to be backed up to reproduce a system, it introduces no additional maintenance overhead, but a symlink to /etc/local is suitable if systems want alltheir configuration under one hierarchy.
Note that /usr/etc is still not allowed: programs in /usr should place configuration files in /etc.