/usr (System Resources)

The /usr hierarchy is for vendor supplied Operating System resources. Except for the /usr/local hierarchy, nothing should modify anything under /usr except the OS package manager.

Software applications must assume that /usr can be read-only. The /usr hierarchy must not be used for volitile data. Except for /usr/local, the /usr hierarchy must not be used for any data that is added or changed outside of package installation/removal as done by the OS package manager. The OS package manager may assume that all of the /usr hierarchy (except /usr/local) is the same mountpoint.

Software being installed outside of the OS package manager should not store data in /usr as this may impede any future invocation of the OS package manager. The /usr/local hierarchy is the exception, and is reserved for software outside of the OS package manager.

/usr/bin (Executables)

Executable files which should appear in the standard search $PATH, and are useful to invoke from a shell. Daemons and executables which are not useful to invoke from a shell instead live in /usr/lib or /usr/libexec.

/usr/include (C/C++ Headers)

The /usr/include directory contains C and C++ header files, usually contained in packages with the -devel suffix.

/usr/lib and /usr/lib64 (Shared libraries)

On Amazon Linux 2023, the /usr/lib64 path is used for 64-bit shared libraries, and package data which is architecture dependent. Since AL2023 does not ship with any 32-bit userspace support, there are only 64-bit shared libraries available.

The /usr/lib path is for static data from OS packages which is compatible with all architectures. This may include executables not usually invoked from a shell, which may also be found in /usr/libexec. Shared libraries are found in /usr/lib64 rather than /usr/lib.

/usr/local (System administrator installed software)

On Amazon Linux 2023, the /usr/local path is available for the system administrator to install software in, software that is not owned by the OS, and will not be touched by the OS. The default /usr/local hierarchy mirrors the / hierarchy.

/usr/share (Shared resources)

Shared resources such as documentation, fonts, and time zone data live in /usr/share. It is common for various specifications to dictate exactly where and in what format data is stored in this directory.

/usr/share/doc (Documentation)

Documentation that comes with packages will be stored in /usr/share/doc.