Manual - Section 5: autofs


autofs - Format of the automounter maps


The automounter maps are FILE, NIS, NISPLUS or LDAP maps referred to by the master map of the automounter (see auto.master(5)). These maps describe how file systems below the mount point of the map (given in the master map) are to be mounted. This page describes the sun map format; if another map format is specified (e.g. hesiod), this documentation does not apply.

Indirect maps can be changed on the fly and the automouter will recognize those changes on the next operation it performs on that map. Direct maps require a HUP signal be sent to the daemon to refresh their contents as does the master map.


This is a description of the text file format. Other methods of specifying these files may exist. All empty lines or lines beginning with # are ignored. The basic format of one line in such maps is:

key [-options] location


For indirect mounts this is the part of the path name between the mount point and the path into the filesystem when it is mounted. Usually you can think about the key as a sub-directory name below the autofs managed mount point.

For direct mounts this is the full path of each mount point. This map is always associated with the /- mount point in the master map.


Zero or more options may be given. Options can also be given in the auto.master file in which case both values are cumulative (this is a difference from SunOS). The options are a list of comma separated options as customary for the mount(8) command. There are two special options -fstype= used to specify a filesystem type if the filesystem is not of the default NFS type. This option is processed by the automounter and not by the mount command. -strict is used to treat errors when mounting file systems as fatal. This is important when multiple file systems should be mounted (‘multi-mounts’). If this option is given, no file system is mounted at all if at least one file system can’t be mounted.


The location specifies from where the file system is to be mounted. In the most cases this will be an NFS volume and the usual notation host:pathname is used to indicate the remote filesystem and path to be mounted. If the filesystem to be mounted begins with a / (such as local /dev entries or smbfs shares) a : needs to be prefixed (e.g. :/dev/sda1).


Indirect map:

kernel    -ro,soft,intr boot      -fstype=ext2        :/dev/hda1 windoze   -fstype=smbfs       ://windoze/c removable -fstype=ext2        :/dev/hdd cd        -fstype=iso9660,ro  :/dev/hdc floppy    -fstype=auto        :/dev/fd0 server    -rw,hard,intr       / -ro \                               /usr \                               /home

In the first line we have a NFS remote mount of the kernel directory on This is mounted read-only. The second line mounts an ext2 volume from a local ide drive. The third makes a share exported from a Windows machine available for automounting. The rest should be fairly self-explanatory. The last entry (the last three lines) is an example of a multi-map (see below).

If you use the automounter for a filesystem without access permissions (like vfat), users usually can’t write on such a filesystem because it is mounted as user root. You can solve this problem by passing the option gid=<gid>, e.g. gid=floppy. The filesystem is then mounted as group floppy instead of root. Then you can add the users to this group, and they can write to the filesystem. Here’s an example entry for an autofs map:

floppy-vfat -fstype=vfat,sync,gid=floppy,umask=002 :/dev/fd0

Direct map:

/nfs/apps/mozilla             bogus:/usr/local/moxill /nfs/data/budgets             tiger:/usr/local/budgets /tst/sbin                     bogus:/usr/sbin


Map Key Substitution

An & character in the location is expanded to the value of the key field that matched the line (which probably only makes sense together with a wildcard key).

Wildcard Key

A map key of * denotes a wild-card entry. This entry is consulted if the specified key does not exist in the map. A typical wild-card entry looks like this:

*         server:/export/home/&

The special character ’&’ will be replaced by the provided key. So, in the example above, a lookup for the key ’foo’ would yield a mount of server:/export/home/foo.

Variable Substitution

The following special variables will be substituted in the key and location fields of an automounter map if prefixed with $ as customary from shell scripts (Curly braces can be used to separate the field name):

ARCH           Architecture (uname -m) CPU            Processor Type HOST           Hostname (uname -n) OSNAME         Operating System (uname -s) OSREL          Release of OS (uname -r) OSVERS         Version of OS (uname -v)

autofs provides additional variables that are set based on the user requesting the mount:

USER           The user login name UID            The user login ID GROUP          The user group name GID            The user group ID HOME           The user home directory HOST           Hostname (uname -n)

Additional entries can be defined with the -Dvariable=Value map-option to automount(8).

Executable Maps

A map can be marked as executable. A program map will be called with the key as an argument. It may return no lines of output if there’s an error, or one or more lines containing a map entry (with \ quoting line breaks). The map entry corresponds to what would normally follow a map key.

An executable map can return an error code to indicate the failure in addition to no output at all. All output sent to stderr is logged into the system logs.

Multiple Mounts

A multi-mount map can be used to name multiple filesystems to mount. It takes the form:

key [-options] [mount-point [-options] location...]...

This may extend over multiple lines, quoting the line-breaks with `#39;. If present, the per-mountpoint mount-options are appended to the default mount-options.

Replicated Server

Multiple replicated hosts, same path: <path> host1,host2,hostn:/path/path

Multiple hosts, some with same path, some with another <path> host1,host2:/blah host3:/some/other/path

Multiple replicated hosts, different (potentially) paths: <path> host1:/path/pathA host2:/path/pathB

Mutliple weighted, replicated hosts same path: <path> host1(5),host2(6),host3(1):/path/path

Multiple weighted, replicated hosts different (potentially) paths: <path> host1(3):/path/pathA host2(5):/path/pathB

Anything else is questionable and unsupported, but these variations will also work: <path> host1(3),host:/blah


This version of the automounter supports direct maps stored in FILE, NIS, NISPLUS and LDAP only.


automount(8), auto.master(5), autofs(8), mount(8).


This manual page was written by Christoph Lameter <>, for the Debian GNU/Linux system. Edited by H. Peter Avian <>, Jeremy Fitzhardinge <> and Ian Kent <>.