automount(1M) NFS R4.11 automount(1M)
NAME
automount - automatically mount NFS file systems
SYNOPSIS
automount [ -mnTv ] [ -D name=value ] [ -f master-file ]
[ -M mount-directory ] [ -tl duration ] [ -tm interval ] [ -tw
interval ]
[ 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 appears to be an NFS server to the kernel.
automount uses the 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 creates 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 the directory argument is a pathname, the map argument must be an
indirect map. In an indirect map the key for each entry is a simple
name that represents a symbolic link within directory to an NFS mount
point.
If the directory argument is `/-', the map that follows must be a
direct map. A direct map is not associated with a single directory.
Instead, the key for each entry is a full pathname that will itself
appear to be a symbolic link to an NFS mount point.
A map can be a file or a Network Interface Service (NIS) map; if a
file, 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 `-'. If these options are
supplied, they become the default mount options for all entries in
the map. Mount options provided within a map entry override these
defaults.
OPTIONS
-m Suppress initialization of directory-map pairs listed in the
auto.master NIS database.
-n Disable dynamic mounts. With this option, references through
the automount daemon only succeed when the target filesystem
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 system
console. Additional output will be appended to
/var/adm/messages.
-v Verbose. Log status and/or warning messages to the console.
-D envar=value
Assign value to the indicated automount (environment)
variable.
-f master-file
Read a local file for initialization, ahead of the auto.master
NIS map.
-M mount-directory
Mount temporary file systems in the named directory, instead
of /tmpmnt.
-tl duration
Specify a duration, in seconds, that a file system is to
remain mounted when not in use. The default is 5 minutes.
-tm interval
Specify an interval, in seconds, between attempts to mount a
filesystem. The default is 30 seconds.
-tw interval
Specify an interval, in seconds, between attempts to unmount
filesystems 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. Environment variables
are expanded only for the automounter's environment -- not for the
environment of a user using the automounter's services.
The special reference to $ARCH expands to the output of uname -m.
This can be useful in creating a map entry for mounting executables
using a server's export pathname that varies according to the
architecture of the client reading the map.
If a reference needs to be protected from affixed characters, you can
surround the variable name with curly braces.
USAGE
Map Entry Format
A simple map entry (mapping) takes the form:
key [ -mount-options ] location ...
where key is the full pathname of the directory to mount when used in
a direct map, or simple name in an indirect map. mount-options is a
comma-separated list of mount options, and location specifies a
remote filesystem from which the directory may be mounted. In the
simple case, location takes the form:
hostname:pathname
Replicated Filesystems
Multiple location fields can be specified for replicated read-only
filesystems, 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.
Since automount does not monitor the status of the server while the
filesystem is mounted it will not use another location in the list if
the currently mounted server crashes. This support for replicated
filesystems is available only at mount time.
If each location in the list shares the same pathname then a single
location may be used with a comma-separated list of hostnames.
hostname,hostname...:pathname
Sharing Mounts
If location is specified in the form:
hostname:pathname:subdir
hostname is the name of the server from which to mount the file
system, pathname 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, automount
mounts homeboy:/home/homeboy, but creates a symbolic link called
/home/able to the able subdirectory in the temporarily-mounted
filesystem. 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/homeboy is already mounted.
With the following map:
able homeboy:/home/homeboy/able
baker homeboy:/home/homeboy/baker
automount would have to mount the filesystem twice.
Comments and Quoting
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.
Characters that have special significance to the automount map parser
may be protected either with double quotes (") or by escaping with a
backslash (\). Pathnames with embedded whitespace, colons (:) or
dollar ($) should be protected.
Directory Pattern Matching
The `&' character is expanded to the value of the key 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 key field, is recognized as
the catch-all entry. Such an entry will be used if any previous
entry has not successfully matched the key being searched for. 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
Multiple Mounts
A multiple mount entry takes the form:
key [ /[mountpoint [ -mount-options ] location ... ] ...
The initial / within the `/[mountpoint]' is required; the optional
mountpoint is taken as a pathname relative to the destination of the
symbolic link for key. If mountpoint is omitted in the first
occurrence, a mountpoint of / is implied.
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. If the mounts are hierarchically related mounts
closer to the root must appear before submounts. All the mounts of a
multiple mount entry will occur together and will be unmounted
together. This is important if the filesystems reference each other
with relative symbolic links. Multiple mount entries can be used
both in direct maps and in indirect maps.
Included Maps
The contents of another map can be included within a map with an
entry of the form:
+mapname
mapname can either be a filename, or the name of an NIS map, or one
of the special maps described below. If the key being searched for
is not located in an included map, the search continues with the next
entry.
Special Maps
There are two special maps currently available: -hosts, and -null.
The -hosts map uses the NIS hosts.byname map to locate a remote host
when the hostname is specified. This map specifies mounts of all
exported file systems from any host. For instance, if the following
automount command is already in effect:
automount /net -hosts
then a reference to /net/hermes/usr would initiate an automatic mount
of all file systems from hermes that automount can mount; references
to a directory under /net/hermes will refer to the corresponding
directory relative to hermes root.
The -null map, when indicated on the command line, cancels any
subsequent map for the directory indicated. It can be used to cancel
a map given in auto.master or for a mount point specified as an entry
in a direct map.
Configuration and the auto.master Map
automount normally consults the auto.master NIS configuration map for
a list of initial automount maps, and sets up automatic mounts for
them in addition to those given on the command line. If there are
duplications, the command-line arguments take precedence over a local
-f master map and they both take precedence over an NIS auto.master
map. This configuration database contains arguments to the automount
command, rather than mappings; unless -f is in effect, automount does
not look for an auto.master file on the local host.
Maps given on the command line, or those given in a local auto.master
file specified with -f override those in the NIS auto.master map.
For instance, given the command:
automount -f /etc/auto.master /home -null /- /etc/auto.direct
and a file named /etc/auto.master that contains:
/home auto.home
automount would ignore /home entry in /etc/auto.master.
FILES
/tmpmnt directory under which filesystems are dynamically
mounted
SEE ALSO
df(1M), ls(1), mount(1M), stat(2), passwd(4),
appropriateprivilege(5).
capdefaults(5).
NOTES
You must have appropriate privilege to execute this command. For
systems supporting the DG/UX Capability Option, appropriate privilege
is defined as having one or more specific capabilities enabled in the
effective capability set of the user. See capdefaults(5) for the
default capabilities for this command.
On systems without the DG/UX Capability Option, appropriate privilege
means that your process has an effective UID of root. See the
appropriateprivilege(5) man page for more information.
The -hosts map must mount all the exported filesystems from a server.
If frequent access to just a single filesystem is required it is more
efficient to access the filesystem with a map entry that is tailored
to mount just the filesystem of interest.
When it receives signal number 1, SIGHUP, 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
/etc/mnttab. The unmounted file system will no longer be monitored
by automount.
An ls(1) listing of the entries in the directory for an indirect map
shows only the symbolic links for currently mounted filesystems.
This restriction is intended to avoid unnecessary mounts as a side
effect of programs that read the directory and stat(2) each of the
names.
Mount points for a single automounter must not be hierarchically
related. automount will not allow an automount mount point to be
created within an automounted filesystem.
automount must not be terminated with the SIGKILL signal (kill -9).
Without an opportunity to unmount itself, the automount mount points
will appear to the kernel to belong to a non-responding NFS server.
The recommended way to terminate automount services is to send a
SIGTERM (kill -15) signal to the daemon. This allows the automounter
to catch the signal and unmount not only its daemon but also any
mounts in /tmpmnt. Mounts in /tmpmnt that are busy will not be
unmounted.
Since each direct map entry results in a separate mount for the mount
daemon such maps should be kept short. Entries added to a direct map
will have no effect until the automounter is restarted.
Entries in both direct and indirect maps can be modified at any time.
The new information will be used when automount next uses the map
entry to do a mount. automount does not cache map entries.
The Network Information Service (NIS) was formerly known as Sun
Yellow Pages (YP). The functionality of the two remains the same;
only the name has changed.
BUGS
The bg mount option is not recognized by the automounter.
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.
Automatically-mounted file systems are mounted with type ignore; they
do not appear in the output of either mount(1M), or df(1).
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