The /usr file system contains executable files that can be shared among machines. The major subdirectories of the /usr directory are shown in the /usr File System diagram.
On a standalone machine the /usr file system is a separate file system (in the /dev/hd2 logical volume). On a diskless or disk-poor machine, a directory from a remote server is mounted with read-only permissions over the local /usr file system. The /usr file system contains read-only commands, libraries, and data.
Except for the contents of the /usr/share directory, the files and directories in the /usr file system can be shared by all machines of the same hardware architecture.
The /usr file system includes the following directories:
|/usr/bin||Contains ordinary commands and shell scripts. For example, the /usr/bin directory contains the ls, cat, and mkdir commands.|
|/usr/ccs||Contains unbundled development package binaries.|
|/usr/include||Contains include, or header, files.|
|/usr/lbin||Contains executable files that are backends to commands.|
|/usr/lib||Contains architecture-independent libraries with names of the form lib*.a. The /lib directory in / (root) is a symbolic link to the /usr/lib directory, so all files that were once in the /lib directory are now in the /usr/lib directory. This includes a few nonlibrary files for compatibility.|
|/usr/lpp||Contains optionally installed products.|
|/usr/sbin||Contains utilities used in system administration, including System Management Interface Tool (SMIT) commands. Most of the commands that once resided in the /etc directory now reside in the /usr/sbin directory.|
|/usr/share||Contains files that can be shared among machines with different architectures. See "Understanding the /usr/share Directory" for more information.|
|/usr/adm||Symbolic link to the /var/adm directory.|
|/usr/mail||Symbolic link to the /var/spool/mail directory.|
|/usr/news||Symbolic link to the /var/news directory.|
|/usr/preserve||Symbolic link to the /var/preserve directory.|
|/usr/spool||Symbolic link to the /var/spool directory.|
|/usr/tmp||Symbolic link to the /var/tmp directory, since the /usr directory is potentially shared by many nodes and is read-only.|
|/usr/dict||Symbolic link to the /usr/share/dict directory.|
|/usr/man||Symbolic link to the /usr/share/man directory.|
|/usr/lpd||Symbolic link to the /usr/lib/lpd directory.|