automount(1M) UNIX System V(NFS) automount(1M)
NAME
automount - automatically mount NFS file systems
SYNOPSIS
automount [-mnTv] [-D name=value] [-M mount-directory] [-f master-file]
[-t sub-options] [directory map [-mount-options] ] . . .
DESCRIPTION
automount is a daemon that automatically and transparently mounts an NFS
file system as needed. It monitors attempts to access directories that
are associated with an automount map, along with any directories or files
that reside under them. When a file is to be accessed, the daemon mounts
the appropriate NFS file system. You can assign a map to a directory
using an entry in a direct
automount map, or by specifying an indirect map on the command line. The
automount daemon resides in /usr/lib/nfs directory.
automount uses a map to locate an appropriate NFS file server, exported
file system, and mount options. It then mounts the file system in a
temporary location, and replaces the file system entry for the directory
or subdirectory with a symbolic link to the temporary location. If the
file system is not accessed within an appropriate interval (five minutes
by default), the daemon unmounts the file system and removes the symbolic
link. If the indicated directory has not already been created, the
daemon creates it, and then removes it upon exiting.
Since the name-to-location binding is dynamic, updates to an automount
map are transparent to the user. This obviates the need to pre-mount
shared file systems for applications that have hard coded references to
files.
If you specify the dummy directory /-, automount treats the map argument
that follows as the name of a direct map. In a direct map, each entry
associates the full pathname of a mount point with a remote file system
to mount.
If the directory argument is a pathname, the map argument points to a
file called an indirect map. An indirect map contains a list of the
subdirectories contained within the indicated directory. With an
indirect map, it is these subdirectories that are mounted automatically.
The map argument must be a full pathname.
The -mount-options argument, when supplied, is a comma-separated list of
mount(1M) options, preceded by a hyphen (-). If mount options are
specified in the indicated map, however, those in the map take
precedence.
Only a privileged user can execute this command.
The following options are available:
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-m Disable the search of the Network Interface Services map file.
(See ``The NIS'' chapter of the Programmer's Guide: Networking
Interfaces.) This option can only be used in conjunction with the
-f option.
-n Disable dynamic mounts. With this option, references through the
automount daemon only succeed when the target file system has been
previously mounted. This can be used to prevent NFS servers from
cross-mounting each other.
-T Trace. Expand each NFS call and display it on the standard output.
-v Verbose. Log status messages to the console.
-D name=value
Assign value to the indicated automount (environment) variable.
-f master-file
Specify all arguments in master-file and instruct the daemon to
look in it for instructions.
-M mount-directory
Mount temporary file systems in the named directory, instead of
/tmpmnt.
-t sub-options
Specify sub-options as a comma-separated list that contains any
combination of the following:
l duration
Specify a duration, in seconds, that a file system is to
remain mounted when not in use. The default is 5 minutes.
m interval
Specify an interval, in seconds, between attempts to mount a
file system. The default is 30 seconds.
w interval
Specify an interval, in seconds, between attempts to unmount
file systems that have exceeded their cached times. The
default is 1 minute.
ENVIRONMENT
Environment variables can be used within an automount map. For instance,
if $HOME appeared within a map, automount would expand it to its current
value for the HOME variable.
If a reference needs to be protected from affixed characters, enclose the
variable name within braces.
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USAGE
Direct/Indirect Map Entry Format
A simple map entry (mapping) takes the form:
directory [ -mount-options ] location ...
where directory is the full pathname of the directory to mount when used
in a direct map, or the basename of a subdirectory in an indirect map.
mount-options is a comma-separated list of mount options, and location
specifies a remote file system from which the directory may be mounted.
In the simple case, location takes the form:
host:pathname
Multiple location fields can be specified, in which case automount sends
multiple mount requests; automount mounts the file system from the first
host that replies to the mount request. This request is first made to
the local net or subnet. If there is no response, any connected server
may respond.
If location is specified in the form:
host:path:subdir
host is the name of the host from which to mount the file system, path is
the pathname of the directory to mount, and subdir, when supplied, is the
name of a
subdirectory to which the symbolic link is made. This can be used to
prevent duplicate mounts when multiple directories in the same remote
file system may be accessed. With a map for /home such as:
able homebody:/home/homebody:able
baker homebody:/home/homebody:baker
and a user attempting to access a file in /home/able, automount mounts
homebody:/home/homebody, but creates a symbolic link called /home/able to
the able subdirectory in the temporarily mounted file system. If a user
immediately tries to access a file in /home/baker, automount needs only
to create a symbolic link that points to the baker subdirectory;
/home/homebody is already mounted. With the following map:
able homebody:/home/homebody/able
baker homebody:/home/homebody/baker
automount would have to mount the file system twice.
A mapping can be continued across input lines by escaping the NEWLINE
with a backslash. Comments begin with a
# and end at the subsequent NEWLINE.
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Directory Pattern Matching
The & character is expanded to the value of the directory field for the
entry in which it occurs. In this case:
able homebody:/home/homebody:&
the & expands to able.
The * character, when supplied as the directory field, is recognized as
the catch-all entry. Such an entry resolves to any entry not previously
matched. For instance, if the following entry appeared in the indirect
map for /home:
* &:/home/&
this would allow automatic mounts in /home of any remote file system
whose location could be specified as:
hostname:/home/hostname
Hierarchical Mappings
A hierarchical mapping takes the form:
directory [/[subdirectory]] [-mount-options] location...
[/[subdirectory] [-mount-options] location...]...
The initial /[subdirectory] is optional for the first location list and
mandatory for all subsequent lists. The optional subdirectory is taken
as a filename relative to the directory. If subdirectory is omitted in
the first occurrence, the / refers to the directory itself.
Given the direct map entry:
/arch/src \
/ -ro,intr arch:/arch/src alt:/arch/src \
/1.0 -ro,intr alt:/arch/src/1.0 arch:/arch/src/1.0 \
/1.0/man -ro,intr arch:/arch/src/1.0/man alt:/arch/src/1.0/man
automount would automatically mount /arch/src, /arch/src/1.0 and
/arch/src/1.0/man, as needed, from either arch or alt, whichever host
responded first.
Direct Maps
A direct map contains mappings for any number of directories. Each
directory listed in the map is automatically mounted as needed. The
direct map as a whole is not associated with any single directory.
Indirect Maps
An indirect map allows you to specify mappings for the subdirectories you
wish to mount under the directory indicated on the command line. It also
obscures local subdirectories for which no mapping is specified. In an
indirect map, each directory field consists of the basename of a
subdirectory to be mounted as needed.
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automount(1M) UNIX System V(NFS) automount(1M)
Included Maps
The contents of another map can be included within a map with an entry of
the form
+mapname
where mapname is a filename.
Special Maps
The -null map is the only special map currently available. The -null
map, when indicated on the command line, cancels a previous map for the
directory indicated.
FILES
/tmpmnt parent directory for dynamically mounted file systems
SEE ALSO
df(1M), mount(1M), passwd(4)
NOTES
Mount points used by automount are not recorded in /etc/mnttab.
mount(1M) on such mount points will fail, saying mount point busy,
although the mount point is not in /etc/mnttab.
Shell filename expansion does not apply to objects not currently mounted.
Since automount is single-threaded, any request that is delayed by a slow
or non-responding NFS server will delay all subsequent automatic mount
requests until it completes.
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