Ubuntu Manpage: autofs - Format of the automounter maps

Provided by: autofs_5.1.1-1ubuntu3.1_amd64

NAME

       autofs - Format of the automounter maps

DESCRIPTION

       The  automounter maps are FILE, NIS, NISPLUS or LDAP maps referred to by the master map of
       the automounter (see auto.master(5)).  These maps describe  how  file  systems  below  the
       mount  point  of the map (given in the master map) are to be mounted.  This page describes
       the sun map format; if another map format, other than amd , is  specified  (e.g.  hesiod),
       this documentation does not apply.

       Indirect  maps,  except  for  the  internal  hosts  map, can be changed on the fly and the
       automouter will recognize those changes on the next operation it  performs  on  that  map.
       Direct  maps  require a HUP signal be sent to the daemon to refresh their contents as does
       the master map.

SUN FORMAT

This is a description of the text file format. Other methods of specifying these files
may exist. All empty lines or lines beginning with # are ignored. The basic format of one
line in such maps is:

key [-options] location

key
For indirect mounts this is the part of the path name between the mount point and
the path into the filesystem when it is mounted. Usually you can think about the
key as a sub-directory name below the autofs managed mount point.

For direct mounts this is the full path of each mount point. This map is always
associated with the /- mount point in the master map.

options
Zero or more options may be given. Options can also be given in the auto.master
file in which case both values are cumulative (this is a difference from SunOS).
The options are a list of comma separated options as customary for the mount(8)
command.

There are several special options

-fstype=
is used to specify a filesystem type if the filesystem is not of the default
NFS type. This option is processed by the automounter and not by the mount
command.

-strict
is used to treat errors when mounting file systems as fatal. This is
important when multiple file systems should be mounted (`multi-mounts'). If
this option is given, no file system is mounted at all if at least one file
system can't be mounted.

-use-weight-only
is used to make the weight the sole factor in selecting a server when
multiple servers are present in a map entry. and

-no-use-weight-only
can be used to negate the option if it is present in the master map entry
for the map but is not wanted for the given mount.

location
The location specifies from where the file system is to be mounted. In the most
cases this will be an NFS volume and the usual notation host:pathname is used to
indicate the remote filesystem and path to be mounted. If the filesystem to be
mounted begins with a / (such as local /dev entries or smbfs shares) a : needs to
be prefixed (e.g. :/dev/sda1).

EXAMPLE

Indirect map:

kernel -ro,soft,intr ftp.kernel.org:/pub/linux
boot -fstype=ext2 :/dev/hda1
windoze -fstype=smbfs ://windoze/c
removable -fstype=ext2 :/dev/hdd
cd -fstype=iso9660,ro :/dev/hdc
floppy -fstype=auto :/dev/fd0
server -rw,hard,intr / -ro myserver.me.org:/ \
/usr myserver.me.org:/usr \
/home myserver.me.org:/home

In the first line we have a NFS remote mount of the kernel directory on ftp.kernel.org.
This is mounted read-only. The second line mounts an ext2 volume from a local ide drive.
The third makes a share exported from a Windows machine available for automounting. The
rest should be fairly self-explanatory. The last entry (the last three lines) is an
example of a multi-map (see below).

If you use the automounter for a filesystem without access permissions (like vfat), users
usually can't write on such a filesystem because it is mounted as user root. You can
solve this problem by passing the option gid=<gid>, e.g. gid=floppy. The filesystem is
then mounted as group floppy instead of root. Then you can add the users to this group,
and they can write to the filesystem. Here's an example entry for an autofs map:

floppy-vfat -fstype=vfat,sync,gid=floppy,umask=002 :/dev/fd0

Direct map:

/nfs/apps/mozilla bogus:/usr/local/moxill
/nfs/data/budgets tiger:/usr/local/budgets
/tst/sbin bogus:/usr/sbin

FEATURES

   Map Key Substitution
       An  & character in the location is expanded to the value of the key field that matched the
       line (which probably only makes sense together with a wildcard key).

   Wildcard Key
       A map key of * denotes a wild-card entry. This entry is consulted  if  the  specified  key
       does not exist in the map.  A typical wild-card entry looks like this:

         *         server:/export/home/&

       The special character '&' will be replaced by the provided key.  So, in the example above,
       a lookup for the key 'foo' would yield a mount of server:/export/home/foo.

   Variable Substitution
       The following  special  variables  will  be  substituted  in  the  location  field  of  an
       automounter map entry if prefixed with $ as customary from shell scripts (curly braces can
       be used to separate the field name):

         ARCH           Architecture (uname -m)
         CPU            Processor Type
         HOST           Hostname (uname -n)
         OSNAME         Operating System (uname -s)
         OSREL          Release of OS (uname -r)
         OSVERS         Version of OS (uname -v)

       autofs provides additional variables that are set based on the user requesting the mount:

         USER           The user login name
         UID            The user login ID
         GROUP          The user group name
         GID            The user group ID
         HOME           The user home directory
         SHOST          Short hostname (domain part removed if present)

       If a program map is used these standard  environment  variables  will  have  a  prefix  of
       "AUTOFS_" to prevent interpreted languages like python from being able to load and execute
       arbitray code from a user home directory.

       Additional entries can be defined with the -Dvariable=Value map-option to automount(8).

   Executable Maps
       A map can be marked as executable. A program map  will  be  called  with  the  key  as  an
       argument.   It  may  return  no  lines of output if there's an error, or one or more lines
       containing a map entry (with \ quoting line breaks). The map  entry  corresponds  to  what
       would normally follow a map key.

       An  executable  map  can  return  an  error code to indicate the failure in addition to no
       output at all.  All output sent to stderr is logged into the system logs.

   Multiple Mounts
       A multi-mount map can be used to name multiple filesystems to mount.  It takes the form:

         key [ -options ] [[/] location [/relative-mount-point [ -options ] location...]...

       This may extend over multiple lines, quoting the line-breaks with `\´.   If  present,  the
       per-mountpoint mount-options are appended to the default mount-options. This behaviour may
       be overridden by the append_options configuration setting.

   Replicated Server
       A mount location can specify multiple hosts for a location, portentially with a  different
       export path for the same file system. Historically these different locations are read-only
       and provide the same replicated file system.

         Multiple replicated hosts, same path:
         <path> host1,host2,hostn:/path/path

         Multiple hosts, some with same path, some with another
         <path> host1,host2:/blah host3:/some/other/path

         Multiple replicated hosts, different (potentially) paths:
         <path> host1:/path/pathA host2:/path/pathB

         Mutliple weighted, replicated hosts same path:
         <path> host1(5),host2(6),host3(1):/path/path

         Multiple weighted, replicated hosts different (potentially) paths:
         <path> host1(3):/path/pathA host2(5):/path/pathB

         Anything else is questionable and unsupported, but these variations will also work:
         <path> host1(3),host:/blah

UNSUPPORTED

       This version of the automounter supports direct maps stored in FILE, NIS, NISPLUS and LDAP
       only.

AMD FORMAT

This is a description of the text file format. Other methods of specifying mount map
entries may be required for different map sources. All empty lines or lines beginning
with # are ignored. The basic format of one line in such maps is:

key location-list

key
A key is a path (or a single path component alone) that may end in the wildcard
key, "*", or the wildcard key alone and must not begin with the "/" character.

location-list
Following the key is a mount location-list.

A location-list list has the following syntax:

location[ location[ ... ]] [|| location[ location[ ... ]]

A mount location-list can use the cut operator, ||, to specify locations that should be
tried if none of the locations to the left of it where selected for a mount attempt.

A mount location consists of an optional colon separated list of selectors, followed by a
colon separated list of option:=value pairs.

The selectors that may be used return a value or boolean result. Those that return a
value may be to used with the comparison operators == and != and those that return a
boolean result may be negated with the !.

For a location to be selected for a mount attempt all of its selectors must evaluate to
true. If a location is selected for a mount attempt and succeeds the lookup is completed
and returns success. If the mount attempt fails the proceedure continues with the next
location until they have all been tried.

In addition some selectors take no argumenets, some one argument and others optionally
take two arguments.

The selectors that take no arguments are:

arch
The machine architecture which, if not set in the confugration, is obtained
using uname(2).

karch
The machine kernel architecture which, if not set in the confugration, is
obtained using uname(2).

os
The operating system name, if not set in the confugration, is obtained using
uname(2).

osver
The operating system version, if not set in the confugration, is obtained
using uname(2).

full_os
The full operating system name, if not set in the confugration this selector
has no value.

vendor
The operating system vendor name, if not set in the confugration this
selector has the value "unknown".

byte
The endianness of the hardware.

cluster
The name of the local cluster. It has a value only if it is set in the
configuration.

autodir
The base path under which external mounts are done if they are needed. Most
mounts are done in place but some can't be and this is the base path under
which those mounts will be done.

domain
The local domain name. It is set to the value of the configuration option
sub_domain. If sub_domain is not given in the configuration it is set to the
domain part of the local host name, as given by gethostname(2).

host
The local host name, without the domain part, as given by gethostname(2).

hostd
The full host name. If sub_domain is given in the configuration this is set
to the contatenation of host and sub_domain deperated by a .. If sub_domain
is not set in the configuration the value of domain is used instead of
sub_domain.

uid
The numeric value of the uid of the user that first requested the mount.
Note this is usual the same as that used by amd but can be different within
autofs.

gid
The numeric value of the gid of the user that first requested the mount.
Note this is usual the same as that used by amd but can be different within
autofs.

key
The string value of the key being looked up.

map
The string value of the map name used to lookup keys.

path
The string value of the full path to the mount being requested.

dollar
Evaluates to the string "$".

The selectors that take one argument are:

in_network(network) , network(network) , netnumber(network) , wire(network)
These selectors are all the same. in_network() is the preferred usage. The
network argument is an address (which may include a subnet mask) or network
name. The function compares network against each interface and returns true
if network belongs to the network the interface is connected to.

xhost(hostname)
The xhost() selector compares hostname to the ${host} and if it doesn't
match it attempts to lookup the cannonical name of hostname and compares it
to {host} as well.

exists(filename)
Returns true if filename exits as determined by lstat(2).

true()
Evaluates to true, the argument is ignored and may be empty.

false()
Evaluates to false, the argument is ignored and may be empty.

The selectors that take up to two arguments are:

netgrp(netgroup[,hostname])
The netgrp() selector returns true if hostname is a member of the netgroup
netgroup. If hostname is not given ${host} is used for the comparison.

netgrpd(netgroup[,hostname])
The netgrpd()i selector behaves the same as netgrp() except that if hostname
is not given ${hostd}, the fully qualified hostname, is used instead of
${host}.

The options that may be used are:

type
This is the mount filesystem type. It can have a value of auto, link,
linkx, host, lofs, ext2-4, xfs, nfs, nfsl or cdfs. Other types that are not
yet implemented or are not available iin autofs are nfsx, lustre, jfs,
program, cachefs and direct.

maptype
The maptype option specifies the type of the map source and can have a value
of file, nis, nisplus, exec, ldap or hesiod. Map sources either not yet
implemented or not available in autofs are sss, ndbm, passwd and union.

fs
The option fs is used to specify the local filesystem. The meaning of this
option (and whether or not it is used) is dependent on the mount filesystem
type.

rhost
The remote host name for network mount requests.

rfs
The remote host filesystem path for network mount requests.

dev
Must resolve to the device file for local device mount requests.

sublink
The sublink option is used to specify a subdirectory within the mount
location to which this entry will point.

pref
The pref option is used to specify a prefix that is prepended to the lookup
key before looking up the map entry key.

opts
The opts option is used to specify mount options to be used for the mount.
If a "-" is given it is ignored. Options that may be used are dependend on
the mount filesystem.

addopts
The addopts option is used to specify additional mount options used in
addition to the default mount options for the mount location.

remopts
The addopts option is used to specify mount options used instead the options
given in opts when the mount location is on a remote retwork.

A number of options aren't available or aren't yet implemented
within autofs, these are:

cache
The cache option isn't used by autofs. The map entry cache is continually
updated and stale entries cleaned on re-load when map changes are detected
so these configuration entries are not used. The regex map key matching is
not implemented and may not be due to the potential overhead of the full map
scans needed on every key lookup.

cachedir
The cachefs filesystem is not available on Linux, a different implementation
is used for caching network mounted file systems.

mount , unmount , umount
These options are used by the amd program mount type which is not yet
implemented.

delay
This option is not used by the autofs implementation and is ignored.

FEATURES

   Key Matching
       The amd parser key matching is unusual.

       The key string to be looked up is constructed by prepending the prefix, if there is one.

       The  resulting  relative  path  string  is matched by first trying the sting itself. If no
       match is found the last component of the key string is replaced  with  the  wilcard  match
       cahracter  ("*") and a wildcard match is attemted. This process continues until a match is
       found or until the last match, against the wilcard match key alone, fails to match  a  map
       entry and the key lookup fails.

   Macro Usage
       Macros are used a lot in the autofs amd implementation.

       Many  of  the  option  values  are set as macro variables corresponding to the option name
       during the map entry parse. So they may  be  used  in  subsequent  option  values.  Beware
       though,  the  order in which option values is not necessarily left to right so you may get
       unexpected results.

EXAMPLE

       Example NFS mount map:

       Assuming we have the autofs master map entry:

         /test     file,amd:/etc/amd.test

       And the following map in /etc/amd.test:

         /defaults type:=nfs;rhost:=bilbo
         apps      rfs:=/autofs
         util      rhost:=zeus;rfs:=/work/util
         local     rfs:=/shared;sublink:=local

       In the first line we have an NFS remote mount of the exported directory /autofs from  host
       bilbo  which  would  be  mounted  on  /test/apps.  Next another nfs mount for the exported
       directory /work/util from host zeus.  This would be mounted on /test/util.

       Finally we have an example of the use of the sublink option. In this case  the  filesystem
       bilbo:/shared  would  be  mounted  on  a  path external the automount directory (under the
       direcory given by configuration option auto_dir) and the path /test/local either symlinked
       or  bind mounted (depending on the setting autofs_use_lofs) to the "local" subdirectory of
       the external mount.

AUTHOR

       This  manual  page  was  written  by  Christoph Lameter <chris@waterf.org>, for the Debian
       GNU/Linux system.  Edited by  H.  Peter  Avian  <hpa@transmeta.com>,  Jeremy  Fitzhardinge
       <jeremy@goop.org> and Ian Kent <raven@themaw.net>.

                                            9 Feb 2014                                  AUTOFS(5)

NAME

DESCRIPTION

SUN FORMAT

EXAMPLE

FEATURES

UNSUPPORTED

AMD FORMAT

FEATURES

EXAMPLE

SEE ALSO

AUTHOR