autofs(1M) autofs(1M)
autofs - install automatic mount points
/usr/etc/autofs [ -v ] [ -t duration ] [ -r ]
autofs is a command that installs AutoFS mount points and associates an
AutoFS map with each mount point. The AutoFS filesystem monitors
attempts to access directories within it and notifies the autofsd(1M)
daemon. The daemon uses the map to locate a filesystem, which it then
mounts at the point of reference within the AutoFS filesystem. If the
filesystem is not accessed within an appropriate interval (five minutes
by default), the autofsd daemon unmounts the filesystem.
AutoFS is started by the /etc/init.d/network script, if the configuration
flags ``nfs'' and ``autofs'' are set ``on'' at system initialization.
(See autofsd(1M).) The script starts the autofsd daemon and invokes the
autofs command. The autofs command consults the master map, a local file
named /etc/auto_master, for a list of AutoFS mount points and their maps.
The master map contains the locations of all AutoFS mount points. By
default, /etc/auto_master contains an entry for the -hosts map:
/hosts -hosts -nosuid
Each entry in the master file specifies a directory on which an AutoFS
mount will be made followed by the AutoFS map to be associated with that
mount point. Mount options may be supplied as an optional third field in
each entry. These options are used for any entries in the map that do
not specify mount options explicitly.
AutoFS maps can be executable binary or script files too. Any AutoFS map
pointing to a file with execute permission set may be considered an
executable map file which the autofs daemon will attempt to execute at
mount time. The output (on stdout) of this executable map file is used as
part of the AutoFS map. Look at the -E option in the autofsd man page for
more information on executable maps.
The autofs command is usually run without arguments. It compares the
entries in /etc/auto_master with the current list of AutoFS mounts in
/etc/mtab and adds, removes or updates AutoFS mounts to bring the
/etc/mtab up to date with /etc/auto_master. At boot time the autofs
command installs all AutoFS mounts from the master map. Subsequently, it
may be run to install AutoFS mounts for new entries in the master map, or
to perform unmounts for entries that have been removed.
-t duration
Specify a duration, in seconds, that a filesystem is to remain
mounted when not in use. The default is 300 (5 minutes).
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-v Verbose mode. Notify of AutoFS mounts, unmounts or other nonessential
information.
-r Remount mode. Force remounting for all existing AutoFS mount
points. Without this key autofs remounts only mount points which
options were changed in /etc/auto_master file. Combination of -r and
-t keys can be used to change unmount timeout for existing AutoFS
mount points.
Map Entry Format
The format for master map entries was discussed above. Entries in other
map files take the form:
key [ -mount-options ] location ...
where key is the full pathname of the directory to mount when used in a
direct map, or the simple name of a subdirectory in an indirect map.
mount-options is a comma-separated list of mount options, and location
specifies a filesystem from which the directory may be mounted. In the
case of a simple NFS mount, location takes the form:
hostname:pathname
hostname is the name of the host from which to mount the filesystem (it
may be omitted if the pathname refers to a local device on which the
filesystem resides) and pathname is the pathname of the directory to
mount. So, /etc/auto_master might contain an entry such as:
/src /etc/auto_src -nosuid
where /etc/auto_src contains:
new awesome:/latest/src
old -ro cave:/archive
Accessing /src/{new,old} would result in a mount of the corresponding
remote filesystem.
Replicated Filesystems [Toc] [Back]
Multiple location fields can be specified for replicated NFS filesystems,
in which case autofs chooses the server that responds first.
If each location in the list shares the same pathname then a single
location may be used with a comma-separated list of hostnames:
hostname1,hostname2...:pathname
A mapping can be continued across input lines by escaping the NEWLINE
with a `\' (backslash). Comments begin with a '#' (pound sign) and end
at the subsequent NEWLINE.
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Map Key Substitution"
The '&' (ampersand) character is expanded to the value of the key field
for the entry in which it occurs. In this case:
whozi onyxserver:/home/&
the & expands to whozi.
Wildcard Key
The '*' (asterisk) character, when supplied as the key field, is
recognized as the catch-all entry. Such an entry will match any key not
previously matched. For instance, if the following entry appeared in the
indirect map for /config:
* &:/public/config/&
this would allow automatic mounts in /config of any remote filesystem
whose location could be specified as:
hostname:/public/config/hostname
Variable Substitution
Client specific variables can be used within an AutoFS map. For
instance, if $HOST appeared within a map, autofs would expand it to its
current value for the client's host name. Supported variables are:
ARCH The output of uname -m. The system's architecture.
For example "IP19"
CPU The output of uname -p. The processor type.
For example "mips"
HOST The output of uname -n. The host name.
For example "ferd"
OSNAME The output of uname -s. The OS name.
For example "IRIX"
OSREL The output of uname -r. The OS release name.
For example "6.2"
OSVERS The output of uname -v. The OS version.
For example "10230951"
If a reference needs to be protected from affixed characters, you can
surround the variable name with '{}' (curly braces).
Multiple Mounts
A multiple mount entry takes the form:
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key [ -mount-options ] [[mountpoint] [-mount-options]
location...]...
The initial /[mountpoint] is optional for the first mount and mandatory
for all subsequent mounts. The optional mountpoint is taken as a
pathname relative to the directory named by key. If mountpoint is omitted
in the first occurrence, a mountpoint of / (root) is implied.
Given an entry in the indirect map for /src:
beta -ro \
/ svr1,svr2:/public/src/beta \
/1.0 svr1,svr2:/public/src/beta/1.0 \
/1.0/man svr1,svr2:/public/src/beta/1.0/man
autofs would automatically mount /src/beta, /src/beta/1.0, and
/src/beta/1.0/man, as needed, from either svr1 or svr2, whichever host
responds first.
Other Filesystem Types [Toc] [Back]
AutoFS assumes NFS Version 3 mounts as the default filesystem type.
Should the server not support NFS V3, AutoFS will retry the mount(s)
using the NFS V2 filesystem type. Users can select a particular version
of the NFS protocol using the vers={2,3} mount option (see fstab(4)).
Other filesystem types can be described using the fstype mount option.
Other mount options specific to this filesystem type can be combined with
the fstype option. The location field must contain information specific
to the filesystem type. If the location field begins with a slash, a
colon character must be prepended.
Mounts using CacheFS are most useful when applied to an entire map as map
defaults. The following entry in the master map describes cached home
directory mounts. It assumes the default location of the cache
directory, /cache.
/home auto_home -fstype=cachefs,backfstype=nfs
The backfstype option is required for CacheFS map entries.
Indirect Maps [Toc] [Back]
An indirect map allows you to specify mappings for the subdirectories you
wish to mount under the directory chosen as the AutoFS mount point. In
an indirect map, each key consists of a simple name (i.e., subdirectory)
that refers to one or more filesystems that are to be mounted as needed.
Direct Maps [Toc] [Back]
Entries in a direct map are associated directly with AutoFS mount points.
Each key is the full pathname of an AutoFS mount point. The direct map
as a whole is not associated with any single directory.
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Included Maps [Toc] [Back]
The contents of another map can be included within a map with an
entry of the form +mapname , or by supplying mapname (without the "+") in
the location field of a map entry. If mapname begins with a slash then
it is assumed to be the pathname of a local file. Otherwise the location
of the map is determined by the policy of the name service switch
according to the entry for the automounter in /etc/nsswitch.conf, such as
automount(dynamic): files nis(nis_enumerate_key) ldap
If the name service is files then the name is assumed to be that of a
local file in /etc. NIS requires the addition of the nis_enumerate_key
attribute; see nis(7P). If the key being searched for is not found in the
included map, the search continues with the next entry subject to control
options. See nsswitch.conf(4). The dynamic attribute is required to
notify the Name Service Daemon (nsd) that the automount map allows
dynamic map creation. See nsd(1M).
Special Maps [Toc] [Back]
There are two special maps available: -hosts and -null. By default, the
-hosts map is used with the /hosts directory. It assumes that the map
key is the hostname of an NFS server. The autofsd daemon dynamically
constructs a map entry from the server's list of exported filesystems.
(See NOTES on -nohide.) For instance a reference to /hosts/bart/usr
would initiate an automatic mount of all exported filesystems from bart
that are mountable by the client. References to a directory under
/hosts/bart will refer to the corresponding directory relative to bart's
root.
The -null map, when indicated in a map entry, cancels a previous map for
the directory indicated. This is most useful in the /etc/auto_master
file for cancelling entries that would otherwise be inherited from the
NIS auto_master map, if included. To be effective, the -null entries must
be inserted before the included map entry.
Configuration and the auto.master File [Toc] [Back]
autofs normally consults the /etc/auto_master configuration file for a
list of initial autofs maps, and sets up automatic mounts for them. This
behavior differs from automount in that autofs does not take maps on the
command line, nor does it look at the auto.master NIS map by default.
Extra mappings (either NIS or file based) should be specified within the
/etc/auto_master configuration file itself. To default to the automount
behavior, for backward compatibility with old automount maps, the user
should have one line in the /etc/auto_master configuration file, pointing
to the NIS auto.master map of the form:
+auto.master
/etc/auto_master master AutoFS map.
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/etc/config/autofs.options
options and arguments for the autofs command and the
autofsd daemon.
autofsd (1M), chkconfig (1M), exports (4), fstab (4), mount (1M),
nsd(1M), nsswitch.conf (4)
The -hosts map mounts all of the exported NFS filesystems, for which the
client has access, from a server. Use the nohide export option on the
server (see exports(4)) to minimize the number of mounts performed by
clients. AutoFS will not request a separate mount for a nohide
filesystem, if the client has access via the parent filesystem. 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.
AutoFS mount points must not be hierarchically related. autofs does not
allow an AutoFS mount point to be created within another AutoFS mount.
Since each direct map entry results in a new AutoFS mount such maps
should be kept short.
If a directory contains direct map mount points then an `ls -l' in the
directory will force all of the direct map mounts to occur.
Entries in both direct and indirect maps can be modified at any time.
The new information is used when autofsd next uses the map entry to do a
mount.
New entries added to a master map or direct map will not be useful until
the autofs command is run to install them as new AutoFS mount points.
New entries added to an indirect map may be used immediately.
An AutoFS directory associated with an indirect map shows only
currently-mounted entries. This is a deliberate policy to avoid
inadvertent mounting of every entry in a map via an `ls -l' of the
directory.
The multiple location feature for NFS mounts allows the autofsd daemon to
choose the most appropriate server at mount time. While such a mount is
in effect, the daemon does not monitor the status of the server. If the
server crashes, autofsd will not select an alternative server from the
list.
Default mount options can be assigned to an entire map when specified as
an optional third field in the master map. These options apply only to
map entries that have no mount options.
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When using NSD to resolve map queries, Autofs actually creates map
directories under the automount directory in /ns/.local. So, the NIS map
auto_home would be created as /ns/.local/automount/auto_home
It is important not to have the execute permission set on a standard text
AutoFS map, as this may cause autofs to attempt to execute the file
assuming that the standard text map file is an executable AutoFS map
file. Look at the -E option in the autofsd man page for more information
on executable maps.
PPPPaaaaggggeeee 7777 [ Back ]
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