Filesystem Hierarchy Standard

3.7 /etc : Host-specific system configuration

3.7.1 Purpose

/etc contains configuration files and directories that are specific to the current system.[footnote 4]

3.7.2 Requirements

No binaries may be located under /etc.

The following directories, or symbolic links to directories are required in /etc:

"Host-specific system configuration"
Configuration for /opt


3.7.3 Specific Options

The following directories, or symbolic links to directories must be in /etc, if the corresponding subsystem is installed:

"Host-specific system configuration"
Configuration for the X Window System (optional)
Configuration for SGML and XML (optional)


The following files, or symbolic links to files, must be in /etc if the corresponding subsystem is installed:[footnote 5]

csh.login Systemwide initialization file for C shell logins (optional)
exports NFS filesystem access control list (optional)
fstab Static information about filesystems (optional)
ftpusers FTP daemon user access control list (optional)
gateways File which lists gateways for routed (optional)
gettydefs Speed and terminal settings used by getty (optional)
group User group file (optional)
host.conf Resolver configuration file (optional)
hosts Static information about host names (optional)
hosts.allow Host access file for TCP wrappers (optional)
hosts.deny Host access file for TCP wrappers (optional)
hosts.equiv List of trusted hosts for rlogin, rsh, rcp (optional)
hosts.lpd List of trusted hosts for lpd (optional)
inetd.conf Configuration file for inetd (optional)
inittab Configuration file for init (optional)
issue Pre-login message and identification file (optional) List of extra directories to search for shared libraries (optional)
motd Post-login message of the day file (optional)
mtab Dynamic information about filesystems (optional)
mtools.conf Configuration file for mtools (optional)
networks Static information about network names (optional)
passwd The password file (optional)
printcap The lpd printer capability database (optional)
profile Systemwide initialization file for sh shell logins (optional)
protocols IP protocol listing (optional)
resolv.conf Resolver configuration file (optional)
rpc RPC protocol listing (optional)
securetty TTY access control for root login (optional)
services Port names for network services (optional)
shells Pathnames of valid login shells (optional)
syslog.conf Configuration file for syslogd (optional)


mtab does not fit the static nature of /etc: it is excepted for historical reasons.[footnote 6]

3.7.4 /etc/opt : Configuration files for /opt Purpose

Host-specific configuration files for add-on application software packages must be installed within the directory /etc/opt/<package>, where <package> is the name of the subtree in /opt where the static data from that package is stored. Requirements

No structure is imposed on the internal arrangement of /etc/opt/<package>.

If a configuration file must reside in a different location in order for the package or system to function properly, it may be placed in a location other than /etc/opt/<package>.


Refer to the rationale for /opt.

3.7.5 /etc/X11 : Configuration for the X Window System (optional) Purpose

/etc/X11 is the location for all X11 host-specific configuration. This directory is necessary to allow local control if /usr is mounted read only. Specific Options

The following files, or symbolic links to files, must be in /etc/X11 if the corresponding subsystem is installed:

Xconfig The configuration file for early versions of XFree86 (optional)
XF86Config The configuration file for XFree86 versions 3 and 4 (optional)
Xmodmap Global X11 keyboard modification file (optional)


Subdirectories of /etc/X11 may include those for xdm and for any other programs (some window managers, for example) that need them.[footnote 7]

3.7.6 /etc/sgml : Configuration files for SGML and XML (optional) Purpose

Generic configuration files defining high-level parameters of the SGML or XML systems are installed here. Files with names *.conf indicate generic configuration files. File with names *.cat are the DTD-specific centralized catalogs, containing references to all other catalogs needed to use the given DTD. The super catalog file catalog references all the centralized catalogs.

[4] The setup of command scripts invoked at boot time may resemble System V, BSD or other models. Further specification in this area may be added to a future version of this standard.

[5] Systems that use the shadow password suite will have additional configuration files in /etc (/etc/shadow and others) and programs in /usr/sbin (useradd, usermod, and others).

[6] On some Linux systems, this may be a symbolic link to /proc/mounts, in which case this exception is not required.

[7] /etc/X11/xdm holds the configuration files for xdm. These are most of the files previously found in /usr/lib/X11/xdm. Some local variable data for xdm is stored in /var/lib/xdm. We recommend that window managers with only one configuration file which is a default .*wmrc file must name it system.*wmrc (unless there is a widely-accepted alternative name) and not use a subdirectory. Any window manager subdirectories must be identically named to the actual window manager binary.

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