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AUTO_MASTER(5) NetBSD File Formats Manual AUTO_MASTER(5)
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auto_master -- auto_master and map file format
The automounter configuration consists of the auto_master configuration
file, which assigns file system 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
The auto_master file consists of lines with two or three entries sepa-
rated by whitespace and terminated by a 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-
[-options] is an optional field that starts with - and can contain
generic file system mount options.
The following example specifies that the /etc/auto_example indirect map
will be mounted on /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
entry 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
The options field, if present, must begin with -. When mounting the file
system, options supplied to auto_master and options specified in the map
entry are concatenated together. The special option fstype is used to
specify file system 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 file system 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.
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)
To pass a location that begins with /, prefix it with a colon. For exam-
This example, when put into /etc/auto_example, and with auto_master
referring to the map as described above, specifies that the NFS share
192.168.1.1:/share/example/x will be mounted on /example/x/ when any
process attempts to access that mountpoint, with intr and nfsv4 mount
options, described in mount_nfs(8):
x -intr,nfsv4 192.168.1.1:/share/example/x
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/ directory without any additional
configuration. Directories for individual NFS servers are not
present until the first access, when they are automatically cre-
-media Query devices that are not yet mounted, but contain valid file
systems. Generally used to access files on removable media.
-noauto Mount file systems 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 VERSUS DIRECT MAPS
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
and this in the /etc/auto_example map file:
/example/x -intr,nfsv4 192.168.1.1:/share/example/x
/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 <trasz@FreeBSD.org> under sponsorship from the FreeBSD
The auto_master configuration file functionality was ported to DragonFly
and NetBSD by Tomohiro Kusumi <email@example.com>.
The -media special map is currently unsupported on NetBSD.
NetBSD 9.3 November 25, 2017 NetBSD 9.3