Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
AUTO_MASTER(5)		    BSD	File Formats Manual		AUTO_MASTER(5)

     auto_master -- auto_master	and map	file format

     The automounter configuration consists of the auto_master configuration
     file, which assigns filesystem paths to map names,	and maps, which	con-
     tain actual mount information.  The auto_master configuration file	is
     used by the automount(8) command.	Map files are read by the
     automountd(8) daemon.

     The auto_master file consists of lines with two or	three entries sepa-
     rated by whitespace and terminated	by newline character:

	   mountpoint map_name [-options]

     mountpoint	is either a fully specified path, or /-.  When mountpoint is a
     full path,	map_name must reference	an indirect map.  Otherwise, map_name
     must reference a direct map.  See MAP SYNTAX below.

     map_name specifies	map to use.  If	map_name begins	with -,	it specifies a
     special map.  See MAP SYNTAX below.  If map_name is not a fully specified
     path (it does not start with /), automountd(8) will search	for that name
     in	/etc.  Otherwise it will use the path as given.	 If the	file indicated
     by	map_name is executable,	automountd(8) will assume it is	an executable
     map.  See MAP SYNTAX below.  Otherwise, the file is opened	and the	con-
     tents parsed.

     -options is an optional field that	starts with - and can contain generic
     filesystem	mount options.

     The following example specifies that the /etc/auto_example	indirect map
     will be mounted on	/example.

	   /example auto_example

     Map files consist of lines	with a number of entries separated by white-
     space and terminated by newline character:

	   key [-options] [mountpoint [-options]] location [...]

     In	most cases, it can be simplified to:

	   key [-options] location

     key is the	path component used by automountd(8) to	find the right map en-
     try to use.  It is	also used to form the final mountpoint.	 A wildcard
     (`*') can be used for the key.  It	matches	every directory	that does not
     match other keys.	Those directories will not be visible to the user un-
     til accessed.

     The options field,	if present, must begin with -.	When mounting the
     filesystem, options supplied to auto_master and options specified in the
     map entry are concatenated	together.  The special option fstype is	used
     to	specify	filesystem type.  It is	not passed to the mount	program	as an
     option.  Instead, it is passed as an argument to mount -t.	 The default
     fstype is `nfs'.  The special option nobrowse is used to disable creation
     of	top-level directories for special and executable maps.

     The optional mountpoint field is used to specify multiple mount points
     for a single key.

     The location field	specifies the filesystem to be mounted.	 Ampersands
     (`&') in the location field are replaced with the value of	key.  This is
     typically used with wildcards, like:


     The location field	may contain references to variables, like:


     Defined variables are:

     ARCH     Expands to the output of uname -p.
     CPU      Same as ARCH.
     DOLLAR   A	literal	$ sign.
     HOST     Expands to the output of uname -n.
     OSNAME   Expands to the output of uname -s.
     OSREL    Expands to the output of uname -r.
     OSVERS   Expands to the output of uname -v.

     Additional	variables can be defined with the -D option of automount(8)
     and automountd(8).

     To	pass a location	that begins with /, prefix it with a colon.  For exam-
     ple, :/dev/cd0.

     This example, when	put into /etc/auto_example, and	with auto_master re-
     ferring to	the map	as described above, specifies that the NFS share will be mounted on /example/x/ when any
     process attempts to access	that mountpoint, with intr and nfsv4 mount op-
     tions, described in mount_nfs(8):

	   x -intr,nfsv4

     Automatically mount an SMB	share on access, as a guest user, without
     prompting for a password:

	   share -fstype=smbfs,-N ://@server/share

     Automatically mount the CD	drive on access:

	   cd -fstype=cd9660 :/dev/cd0

     Special maps have names beginning with -.	Supported special maps are:

     -hosts  Query the remote NFS server and map exported shares.  This	map is
	     traditionally mounted on /net.  Access to files on	a remote NFS
	     server is provided	through	the /net/nfs-server-ip/share-name/ di-
	     rectory without any additional configuration.  Directories	for
	     individual	NFS servers are	not present until the first access,
	     when they are automatically created.
     -media  Query devices that	are not	yet mounted, but contain valid
	     filesystems.  Generally used to access files on removable media.
	     Mount filesystems configured in fstab(5) as "noauto".  This needs
	     to	be set up as a direct map.
     -null   Prevent automountd(8) from	mounting anything on the mountpoint.

     It	is possible to add custom special maps by adding them, as executable
     maps named	special_foo, to	the /etc/autofs/ directory.

     If	the map	file specified in auto_master has the execute bit set,
     automountd(8) will	execute	it and parse the standard output instead of
     parsing the file contents.	 When called without command line arguments,
     the executable is expected	to output a list of available map keys sepa-
     rated by newline characters.  Otherwise, the executable will be called
     with a key	name as	a command line argument.  Output from the executable
     is	expected to be the entry for that key, not including the key itself.

     Indirect maps are referred	to in auto_master by entries with a fully
     qualified path as a mount point, and must contain only relative paths as
     keys.  Direct maps	are referred to	in auto_master by entries with /- as
     the mountpoint, and must contain only fully qualified paths as keys.  For
     indirect maps, the	final mount point is determined	by concatenating the
     auto_master mountpoint with the map entry key and optional	map entry
     mountpoint.  For direct maps, the final mount point is determined by con-
     catenating	the map	entry key with the optional map	entry mountpoint.

     The example above could be	rewritten using	direct map, by placing this in

	   /- auto_example

     and this in /etc/auto_example map file:

	   /example/x -intr,nfsv4
	   /example/share -fstype=smbfs,-N ://@server/share
	   /example/cd -fstype=cd9660 :/dev/cd0

     Both auto_master and maps may contain entries consisting of a plus	sign
     and map name:


     Those entries cause automountd(8) daemon to retrieve the named map	from
     directory services	(like LDAP) and	include	it where the entry was.

     If	the file containing the	map referenced in auto_master is not found,
     the map will be retrieved from directory services instead.

     To	retrieve entries from directory	services, automountd(8)	daemon runs
     /etc/autofs/include, which	is usually a shell script, with	map name as
     the only command line parameter.  The script should output	entries	for-
     matted according to auto_master or	automounter map	syntax to standard
     output.  An example script	to use LDAP is included	in
     /etc/autofs/include_ldap.	It can be symlinked to /etc/autofs/include.

     /etc/auto_master  The default location of the auto_master file.
     /etc/autofs/      Directory containing shell scripts to implement special
		       maps and	directory services.

     autofs(5),	automount(8), automountd(8), autounmountd(8)

     The auto_master configuration file	functionality was developed by Edward
     Tomasz Napierala <> under	sponsorship from the FreeBSD

BSD			       December	28, 2018			   BSD


Want to link to this manual page? Use this URL:

home | help