automount(1M) MISC. REFERENCE MANUAL PAGES automount(1M)
NAME
automount - automatically mount NFS file systems
SYNOPSIS
automount [-nTv] [-D name=value] [-M mount-directory] [-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.
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 sys-
tem 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 sub-
directories that are mounted automatically. The map argu-
ment 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.
The following options are available:
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-n Disable dynamic mounts. With this option, references
through the automount daemon only succeed when the tar-
get 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.
-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 con-
tains 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 charac-
ters, enclose the variable name within braces.
USAGE
Direct/Indirect Map Entry Format
A simple map entry (mapping) takes the form:
directory [ -mount-options ] location ...
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where directory is the full pathname of the directory to
mount when used in a direct map, or the basename of a sub-
directory 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 homeboy:/home/homeboy:able
baker homeboy:/home/homeboy:baker
and a user attempting to access a file in /home/able, auto-
mount mounts homeboy:/home/homeboy, but creates a symbolic
link called /home/able to the able subdirectory in the tem-
porarily 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 subdirec-
tory; /home/homeboy is already mounted. With the following
map:
able homeboy:/home/homeboy/able
baker homeboy:/home/homeboy/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 homeboy:/home/homeboy:&
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] loca-
tion... [/[subdirectory] [-mount-options] loca-
tion...]...
The initial /[subdirectory] is optional for the first loca-
tion 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 direc-
tories. Each directory listed in the map is automatically
mounted as needed. The direct map as a whole is not associ-
ated with any single directory.
Indirect Maps
An indirect map allows you to specify mappings for the sub-
directories you wish to mount under the directory indicated
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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.
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
When it receives signal number 1, automount rereads the
/etc/mnttab file 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 file.
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.
Programs that read /etc/mnttab and then touch files that
reside under automatic mount points will introduce further
entries to the file.
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