Filesystem Hierarchy Standard

3.12 /opt : Add-on application software packages

3.12.1 Purpose

/opt is reserved for the installation of add-on application software packages.

A package to be installed in /opt must locate its static files in a separate /opt/<package> directory tree, where <package> is a name that describes the software package.

3.12.2 Requirements

"Add-on application software packages"
Static package objects


The directories /opt/bin, /opt/doc, /opt/include, /opt/info, /opt/lib, and /opt/man are reserved for local system administrator use. Packages may provide "front-end" files intended to be placed in (by linking or copying) these reserved directories by the local system administrator, but must function normally in the absence of these reserved directories.

Programs to be invoked by users must be located in the directory /opt/<package>/bin. If the package includes UNIX manual pages, they must be located in /opt/<package>/man and the same substructure as /usr/share/man must be used.

Package files that are variable (change in normal operation) must be installed in /var/opt. See the section on /var/opt for more information.

Host-specific configuration files must be installed in /etc/opt. See the section on /etc for more information.

No other package files may exist outside the /opt, /var/opt, and /etc/opt hierarchies except for those package files that must reside in specific locations within the filesystem tree in order to function properly. For example, device lock files must be placed in /var/lock and devices must be located in /dev.

Distributions may install software in /opt, but must not modify or delete software installed by the local system administrator without the assent of the local system administrator.


The use of /opt for add-on software is a well-established practice in the UNIX community. The System V Application Binary Interface [AT&T 1990], based on the System V Interface Definition (Third Edition), provides for an /opt structure very similar to the one defined here.

The Intel Binary Compatibility Standard v. 2 (iBCS2) also provides a similar structure for /opt.

Generally, all data required to support a package on a system must be present within /opt/<package>, including files intended to be copied into /etc/opt/<package> and /var/opt/<package> as well as reserved directories in /opt.

The minor restrictions on distributions using /opt are necessary because conflicts are possible between distribution-installed and locally-installed software, especially in the case of fixed pathnames found in some binary software.


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Translated by troff2html v1.5 on 29 March 2002 by Daniel Quinlan