automount(8) System Manager's Manual automount(8)
NAME
automount - Automatically and transparently mounts and unmounts NFS file systems
SYNOPSIS
/usr/sbin/automount [-hmnpTv] [-D name=value] [-f master-file] [-M mount-directory] [-tl duration] [-tm interval] [-tw interval] [directory
map [-mount-options]]
OPTIONS
Includes the host name in mount-point pathnames. The host name is inserted just after the mount-directory in a mount-point pathname. This
ensures that NFS mount points to different servers are placed in separate directories. This avoids a limitation of getwd(3). Ignores
directory-mapname pairs listed in the auto.master NIS database. Disables dynamic mounts. Lookups intercepted by the automount daemon suc-
ceed only when the target file system has been previously mounted. Uses local mounts for primary Internet addresses and NFS loopback
mounts for Internet alias addresses. Without this option, the command's default behavior is to bypass NFS for all local Internet
addresses, including Internet alias addresses. Traces all NFS requests received by the daemon. Information about the details of the
request are expanded and sent to standard output. Logs status messages to the console. (Stands for "verbose.") Defines an automount
environment variable by assigning value to the variable. Uses master-file for a list of initial directory to mapname pairs, ahead of the
auto.master NIS map. If an entry exists in both master-file and auto.master, the one specified in master-file is used since it is read
first. Similarly, entries on the command line take precedence over master-file entries. This technique can be used to replace entries in
global maps with your own. Uses mount-directory instead of the default, /tmp_mnt. Specifies a duration (in seconds) that a file system is
to remain mounted when not in use. The default is 5 minutes. Specifies an interval (in seconds) between attempts to mount a file system.
The default is 30 seconds. Specifies an interval (in seconds) between attempts to unmount file systems that have exceeded their cached
times. The default is 1 minute. Specifies the full pathname of a local directory if the map argument is the name of an indirect map or the
name of a special map. If the map argument is the name of a direct map, the dummy directory "/-" is specified as the directory. Names a
map that the automount command uses to find the mount points and locations. This can either be a file name, an NIS map name, or a special
map name. Specifies the mount options to be applied to all of the directories listed in map. If mount options are listed in the specified
map, they take precedence over these options.
DESCRIPTION
The automount daemon automatically and transparently mounts and unmounts NFS file systems on an as-needed basis. It provides an alterna-
tive to using /etc/fstab for NFS mounting file systems on client machines. (See autofsd(8) for another alternative.)
The automount daemon can be started from the /etc/rc.config.common file or from the command line. Once started, it sleeps until a user
attempts to access a directory that is associated with an automount map, or any directory or file in the directory structure. The daemon
awakes and consults the appropriate map and mounts the NFS file system. By default, the daemon mounts the remote file system under the
directory /tmp_mnt and creates a symbolic link to the temporary mount point. If the indicated directory has not already been created, the
daemon creates it and removes it after automatic unmount. After a specified period of inactivity on a file system, 5 minutes by default,
the automount daemon unmounts that file system.
The maps indicate where to find the file system to be mounted and the mount options to use. The names of the maps are passed to automount
from the command line or from a master map. If the command line and the master map contain contradictory arguments, the command line argu-
ments take precedence.
Note
The automount program reads the master map only at startup. If you make any changes to the master map, you must restart automount.
An individual automount map is either local or served by NIS. A system, however, can use both local and NIS automount maps. When a map is
referenced, the automount daemon checks whether a full pathname is specified. If it is, automount looks for the designated mapname
locally. If the mapname is not a full pathname, automount looks for an NIS map by that name.
By default, automount uses UDP. If the tcp option is specified in a map, automount will try TCP. If TCP is not available, automount will
then use UDP.
Maps
Conventionally, automount maps are files that are located in the /etc directory with names that have the prefix auto. They indicate which
remote file systems to mount, where to mount them, and which options to use.
The Master Map
The automount program can consult a master map, which contains entries that point to other maps that can be either direct or indirect. If
NIS is running, automount checks for the presence of an NIS map named auto.master; you are not required to run NIS or have an auto.master
map. A master map can also be a file whose location is specified with the -f command line option.
The master map provides automount with a list of maps, and with arguments that pertain to each of the maps. Each line in the master map has
the following syntax: directory map [mount-options]
Specifies the full pathname of a local directory if the map argument is the name of an indirect map or the name of a special map. If the
map argument is the name of a direct map, the dummy directory "/-" is specified as the directory. Names the map that the automount command
uses to find the mount points and locations. This can either be a file name, an NIS map name, or a special map name. Lists the options
used to regulate the mounting of entries listed in map.
Direct Maps
Direct maps specify which remote file systems to mount locally and what the local mount points are. They also can specify mount options.
Direct maps have the following syntax: key [mount-options] location
Specifies the full pathname of the mount point. Lists the options for this specific mount. When present, these options override any mount
options specified on the command line or in the master map. Specifies the location of the resource being mounted and uses the format
server:pathname. Multiple location fields can be specified; see Replicated File Systems for more information.
Indirect Maps
Indirect maps have the same format as direct maps. However, unlike the key in a direct map, the key in an indirect map is a simple name
that does not begin with a slash. (Remember that the indirect map as a whole has been associated with a directory specified in the master
map or on the command line. The entries in an indirect map list subdirectories that are individually mounted within the directory associ-
ated with the map.)
Special Maps
The -hosts map is a special automount map that is used to access all directories exported by a server to a client.
The following command allows a client to access directories that are exported from any host in its /etc/hosts file, the NIS hosts database:
# automount /net -hosts
For example, suppose that hera and sheba are both hosts on a local area network that is running NIS. If superuser on hera enters the auto-
mount /net -hosts command, users on hera can access any directories that sheba exports to hera. All of the exported directories are mounted
under /net/sheba on hera.
The -null map, when indicated on the command line, cancels the map associated with the directory indicated. It can be used to cancel a map
specified in the master map. For example, invoking the automount command in the following manner causes the /net entry in auto.master to
be ignored: # automount /net -null
Pattern Matching
The ampersand (&) is expanded into the key field in a map wherever it appears. In the following example, the ampersand (&) expands to oak:
#key mount_options location # oak &:/export/&
The asterisk (*), when supplied as the key field, is recognized as the catch-all entry. It is used to substitute for lines that are all
formatted similarly. Any entry following the asterisk is ignored. In the following example, the automount program uses the asterisk to
match any host name other than oak:
#key mount_options location # oak &:/export/& * &:/home/&
Environment Variables
The value of an environment variable can be used within an automount map by prefixing a dollar sign ($) to its name. You can also use
braces to delimit the name of the variable from appended letters or digits. The environment variables can be inherited from the environment
or can be explicitly defined with the -D command line option.
Multiple Mounts
A multiple mount entry causes several NFS mount points to be mounted and unmounted together. Multiple mounts have the following syntax:
key mountpoint [mount-options] location...
[mountpoint [mount-options] location...] ...
Specifies the full pathname or simple name of the mount point, depending on whether it is a direct or indirect map entry. Specifies the
full pathname of a local directory. All mount points must begin with a slash (/). A slash is acceptable as the first mountpoint. Lists the
options for this specific mount. When present, these options override any mount options specified on the command line or in the master map.
Specifies the location of the resource being mounted and uses the format server:pathname. Multiple location fields can be specified; see
Replicated File Systems for more information.
If multiple mounts are hierarchically related, the order in which they appear in the entry is the order in which they are mounted.
In the following example, the directories /usr/local, /usr/local/bin, /usr/local/src, and /usr/local/tools are mounted from the machines
host1, host2, host3, and host4, respectively. When the root of the hierarchy is referenced, the automount program mounts the whole hierar-
chy.
/usr/local
/ -ro host1:/usr/local
/bin -ro host2:/usr/local/bin
/src -ro host3:/usr/local/src
/tools -ro host4:/usr/src/tools
Readability has been improved by splitting the entry into five lines and indenting the continuation lines.
Shared Mounts
A shared mount prevents duplicate mounts of a remote file system by creating symbolic links for subdirectories that the file system con-
tains. When you mount multiple directories from within a common remote directory, you can specify the location field as follows:
host:path:subdir
Specifies the remote host from which to mount the file system. Specifies a pathname for the common directory that contains the directories
you want to mount. Specifies the name of a subdirectory to which you want to make a symbolic link.
Suppose an indirect map called /auto.myindirect is specified in a master file as follows:
/mydir /auto.myindirect
And the /auto.myindirect map consists of the following entries:
mybin host1:/usr/staff/diane:bin mystuff host1:/usr/staff/diane:stuff
When a user accesses a file in /mydir/mybin, the automount daemon mounts host1:/usr/staff/diane, but creates a symbolic link called
/mydir/mybin to the bin subdirectory in the temporarily mounted file system. If a user immediately tries to access a file in
/mydir/mystuff, the automount daemon needs only to create a symbolic link that points to the stuff subdirectory because the
/usr/staff/diane directory is already mounted. With the following map, the daemon would perform two separate mount operations:
mybin host1:/usr/staff/diane/bin mystuff host1:/usr/staff/diane/stuff
Replicated File Systems
You can specify multiple locations for a single mount. If a file system is located on several servers and one of the servers is disabled,
the file system can be mounted from one of the other servers. This makes sense only when mounting a read-only file system.
In the following example, the reference pages can be mounted from host1, machine2, or system3:
/usr/man
-ro,soft host1:/usr/man
machine2:/usr/man
system3:/usr/man
The preceding example can also be expressed as a list of servers, separated by commas and followed by a colon and the pathname, for exam-
ple:
/usr/man -ro,soft host1,machine2,system3:/usr/man
This syntax is valid only if the pathname is the same on each server.
When you access the reference pages, the automount daemon issues a ping (NFS v2 noop request) to each of the specified servers concur-
rently. The server that first responds to the ping request is used for the mount.
NOTES
Sending the SIGTERM signal (kill -TERM) to the automount daemon causes it to unmount all file systems that it has mounted, and to exit.
This is the preferred method. If you send any other signals that automount cannot catch (for example, kill -KILL or kill -INT), any NFS
mount points that automount was not able to remove before exiting will hang. The hang will occur from any program that attempts to access
those mount points. You must reboot the system in order to remove the NFS mount points.
Sending the SIGHUP signal to the automount daemon causes it to reread the system mount table to update its internal record of currently
mounted file systems. If a file system mounted with automount is unmounted by a umount command, automount should be forced to reread the
system mount table.
RESTRICTIONS
Shell filename expansion does not apply to objects not currently mounted.
Because automount is singlethreaded, any request that is delayed by a slow or nonresponding NFS server will delay all subsequent automount
requests until the delayed request has been completed.
EXAMPLES
The following is a sample auto.master map:
# # mount-point mapname mount-options # /net -hosts /home auto.indirect
-rw /- auto.direct -ro,intr The following is a typical automount indirect map:
# # key mount-options location # john merge:/usr/staff/john mary
stripe:/usr/staff/mary fred blur:/usr/staff/fred The following is a typical automount direct
map:
# # key mount-options location # /usr/source -ro merge:/usr/src/proto /usr/local
blur:/usr/bin/tools The following is a sample indirect map that specifies multiple mount locations for the file system reference.
The file system is mounted from the first server to respond to the mount request.
reference -ro earl:/usr/src/ref
fern:/usr/staff/ron/ref
irv:/usr/backup/reference
FILES
Directory where automounted file systems reside.
SEE ALSO
Commands: autofsd(8), autofsmount(8), mount(8)
Network Administration
automount(8)