auto.master(5) — Linux manual page


AUTO.MASTER(5)             File Formats Manual            AUTO.MASTER(5)

NAME         top

       auto.master - Master Map for automounter consulted by autofs

DESCRIPTION         top

       The auto.master map is consulted to set up automount managed
       mount points when the autofs(8) script is invoked or the
       automount(8) program is run. Each line describes a mount point
       and refers to an autofs map describing file systems to be mounted
       under the mount point.

       The default location of the master map is @mapdir@/auto.master
       but an alternate name may be given on the command line when
       running the automounter and the default master map may changed by
       setting the MASTER_MAP_NAME configuration variable in
       @confdir@/autofs.  If the master map name has no path then the
       system Name Service Switch configuration will be consulted and
       each of the sources searched in line with the rules given in the
       Name Service Switch configuration.

       Access to mounts in maps is governed by a key.

       For direct maps the mount point is always specified as:


       and the key used within the direct map is the full path to the
       mount point. The direct map may have multiple entries in the
       master map.

       For indirect maps access is by using the path scheme:


       where mount-point is one of the entries listed in the master map.
       The key is a single directory component and is matched against
       entries in the map given in the entry (See autofs(5)).

       Additionally, a map may be included from its source as if it were
       itself present in the master map by including a line of the form:

       +[maptype[,format]:]map [options]

       and automount(8) will process the map according to the
       specification described below for map entries. Plus map inclusion
       is only permitted in file map sources.  Indirect map entries must
       be unique in the master map so second and subsequent entries for
       an indirect mount point are ignored by automount(8).

       NOTE:  autofs currently does not collapse multiple slashes in
              paths, so it is important to ensure paths used in maps are
              correct. If unnecessary multiple slashes are present in a
              path it can lead to unexpected failures such as an
              inability to expire automounts. An exception to this is a
              trailing slash at the end of the automount point path in
              the master map which will be removed if present.

FORMAT         top

       Master map entries have three fields separated by an arbitrary
       number of spaces or tabs. Lines beginning with # are comments.
       The first field is the mount point described above and the second
       field is the name of the map to be consulted for the mount point
       followed by the third field which contains options to be applied
       to all entries in the map.

       The format of a master map entry is:

       mount-point [map-type[,format]:]map [options]

              Base location for the autofs filesystem to be mounted.
              For indirect maps this directory will be created (as with
              mkdir -p) and is removed when the autofs filesystem is

              Type of map used for this mount point.  The following are
              valid map types:

              file   The map is a regular text file.

                     The map is an executable program, which is passed a
                     key on the command line and returns an entry
                     (everything besides the key) on stdout if
                     successful.  Optinally, the keyword exec may be
                     used as a synonym for program to avoid confusion
                     with amd formated maps mount type program.

              yp     The map is a NIS (YP) database.

                     The map is a NIS+ database.

              hesiod The map is a hesiod database whose filsys entries
                     are used for maps.

              ldap or ldaps
                     The map is stored in an LDAP directory. If ldaps is
                     used the appropriate certificate must be configured
                     in the LDAP client.

              multi  This map type allows the specification of multiple
                     maps separated by "--". These maps are searched in
                     order to resolve key lookups.

              dir    This map type can be used at + master map including
                     notation. The contents of files under given
                     directory are included to the master map. The name
                     of file to be included must be ended with
                     ".autofs". A file will be ignored if its name is
                     not ended with the suffix. In addition a dot file,
                     a file which name is started with "." is also

              Format of the map data; currently the formats recognized
              are sun, which is a subset of the Sun automounter map
              format, hesiod, for hesiod filesys entries and amd for amd
              formated map entries.  If the format is left unspecified,
              it defaults to sun for all map types except hesiod unless
              it is a top level amd mount that has a configuration entry
              for the mount point path, in which case the format used is

              Name of the map to use.  This is an absolute UNIX pathname
              for maps of types file, dir, or program, and the name of a
              database in the case for maps of type yp, nisplus, or
              hesiod or the dn of an LDAP entry for maps of type ldap.

              Any remaining command line arguments without leading
              dashes (-) are taken as options (-o) to mount.  Arguments
              with leading dashes are considered options for the maps
              and are passed to automount (8).

              The sun format supports the following options:

                     Replace variable with value in map substitutions.

                     Treat errors when mounting file systems as fatal.
                     This is important when multiple file systems should
                     be mounted (`multimounts'). If this option is
                     given, no file system is mounted at all if at least
                     one file system can't be mounted.

                     This is an autofs specific option that is a pseudo
                     mount option and so is given without a leading
                     dash. Use of the browse option pre-creates mount
                     point directories for indirect mount maps so the
                     map keys can be seen in a directory listing without
                     being mounted. Use of this option can cause
                     performance problem if the indirect map is large so
                     it should be used with caution. The internal
                     program default is to enable browse mode for
                     indirect mounts but the default installed
                     configuration overrides this by setting BROWSE_MODE
                     to "no" because of the potential performance
                     problem. This option does the same as the
                     deprecated --ghost option, the browse option is
                     preferred because it is used by other autofs

              nobind This is an autofs specific option that is a pseudo
                     mount option and so is given without a leading
                     dash. It may be used either in the master map entry
                     (so it effects all the map entries) or with
                     individual map entries to prevent bind mounting of
                     local NFS filesystems. For direct mount maps the
                     option is only effective if specified on the first
                     direct map entry and is applied to all direct mount
                     maps in the master map. It is ignored if given on
                     subsequent direct map entries. It may be used on
                     individual map entries of both types. Preventing
                     bind mounts of NFS file systems can no longer be
                     done by using the "port=" option, the nobind option
                     must be used instead.

                     This option makes bind mounting use a symlink
                     instead of an actual bind mount. It is an autofs
                     specific option that is a pseudo mount option and
                     so is given without a leading dash. It may be used
                     with indirect map entries only, either in the
                     master map (so it effects all map entries) or with
                     individual map entries. The option is ignored for
                     direct mounts and non-root offest mount entries.

                     Use a strict expire policy for this automount.
                     Using this option means that last use of autofs
                     directory entries will not be updated during path
                     walks so that mounts in an automount won't be kept
                     mounted by applications scanning the mount tree.
                     Note that this doesn't completely resolve the
                     problem of expired automounts being immediately re-
                     mounted due to application accesses triggered by
                     the expire itself.

              slave, private or shared
                     This option allows mount propagation of bind mounts
                     to be set to slave, private or shared. This option
                     defaults to slave if no option is given. When using
                     multi-mounts that have bind mounts the bind mount
                     will have the same properties as its parent which
                     is commonly propagation shared. And if the mount
                     target is also propagation shared this can lead to
                     a deadlock when attempting to access the offset
                     mounts. When this happens an unwanted offset mount
                     is propagated back to the target file system
                     resulting in a deadlock since the automount target
                     is itself an (unwanted) automount trigger.  This
                     option is an autofs pseudo mount option that can be
                     used in the master map only.

              -r, --random-multimount-selection
                     Enables the use of random selection when choosing a
                     host from a list of replicated servers. This option
                     is applied to this mount only, overriding the
                     global setting that may be specified on the command

              -w, --use-weight-only
                     Use only specified weights for server selection
                     where more than one server is specified in the map
                     entry. If no server weights are given then each
                     available server will be tried in the order listed,
                     within proximity.

              -t, --timeout <seconds>
                     Set the expire timeout for map entries. This option
                     can be used to override the global default given
                     either on the command line or in the configuration.

              -n, --negative-timeout <seconds>
                     Set the timeout for caching failed key lookups.
                     This option can be used to override the global
                     default given either on the command line or in the

              --mode <octal_mode>
                     Set the directory mode for the base location of the
                     autofs mount point.  If this option is given,
                     autofs will chmod that directory with this mode.

BUILTIN MAP -hosts         top

       If "-hosts" is given as the map then accessing a key under the
       mount point which corresponds to a hostname will allow access to
       the exports of that host. The hosts map cannot be dynamically
       updated and requires a HUP signal to be sent to the daemon for it
       to check hosts for an update. Due to possible hierarchic
       dependencies within a mount tree, it might not be completely
       updated during the HUP signal processing.

       For example, with an entry in the master map of /net -hosts
       accessing /net/myserver will mount exports from myserver on
       directories below /net/myserver.

       NOTE: mounts done from a hosts map will be mounted with the
       "nosuid,nodev" options unless overridden by explicitly specifying
       the "suid", "dev" options in the master map entry.

BUILTIN MAP -null         top

       If "-null" is given as the map it is used to tell automount(8) to
       ignore a subsequent master map entry with the given path.

       It can only be used for paths that appear in the master map (or
       in direct mount maps).

       An indirect mount map top level mount point path can be nulled.
       If so no mounts from the nulled mount are performed (essentially
       it isn't mounted).

       Direct mount map path entries can be nulled. Since they must be
       present at startup they are (notionally) part of the master map.

       A nulled master map entry path will ignore a single subsequent
       matching entry. Any matching entry following that will be treated
       as it normally would be. An example use of this is allowing local
       master map entries to override remote ones.

       NOTE: If a duplicate master map entry path is seen (excluding
       paths of null entries) it will be ignored and noted in the log,
       that is the first encountered master map entry is used unless
       there is a corresponding null entry.

LDAP MAPS         top

       If the map type ldap is specified the mapname is of the form
       [//servername/]dn, where the optional servername is the name of
       the LDAP server to query, and dn is the Distinguished Name of a
       subtree to search for map entries.  The old style
       ldap:servername:mapname is also understood. Alternatively, the
       type can be obtained from the Name Service Switch configuration,
       in which case the map name alone must be given.

       If no schema is set in the autofs configuration then autofs will
       check each of the commonly used schema for a valid entry and if
       one is found it will be used for subsequent lookups.

       There are three common schemas in use:

              Entries in the nisMap schema are nisObject objects in the
              specified subtree, where the cn attribute is the key (the
              wildcard key is "/"), and the nisMapEntry attribute
              contains the information used by the automounter.

              The automountMap schema has two variations that differ in
              the attribute used for the map key. Entries in the
              automountMap schema are automount objects in the specified
              subtree, where the cn or automountKey attribute (depending
              on local usage) is the key (the wildcard key is "/"), and
              the automountInformation attribute contains the
              information used by the automounter. Note that the cn
              attribute is case insensitive.

       The object classes and attributes used for accessing automount
       maps in LDAP can be changed by setting entries in the autofs
       configuration located in @confdir@/autofs.conf.

       NOTE:  If a schema is given in the configuration then all the
              schema configuration values must be set, any partial
              schema specification will be ignored.

       For amd format maps a different schema is used:

              The amdmap schema contains attributes amdmapName,
              amdmapKey and amdmapValue where amdmapName contains the
              name of the containing map, amdmapKey contains the map key
              and amdmapValue contains the map entry.


       LDAP authenticated binds, TLS encrypted connections and
       certification may be used by setting appropriate values in the
       autofs authentication configuration file and configuring the LDAP
       client with appropriate settings.  The default location of this
       file is @mapdir@/autofs_ldap_auth.conf.

       If this file exists it will be used to establish whether TLS or
       authentication should be used.

       An example of this file is:

         <?xml version="1.0" ?>

       If TLS encryption is to be used the location of the Certificate
       Authority certificate must be set within the LDAP client
       configuration in order to validate the server certificate. If, in
       addition, a certified connection is to be used then the client
       certificate and private key file locations must also be
       configured within the LDAP client.

       In OpenLDAP these may be configured in the ldap.conf file or in
       the per-user configuration. For example, it may be sensible to
       use the system wide configuration for the location of the
       Certificate Authority certificate and set the location of the
       client certificate and private key in the per-user configuration.
       The location of these files and the configuration entry
       requirements is system dependent so the documentation for your
       installation will need to be consulted to get further

       See autofs_ldap_auth.conf(5) for more information.

EXAMPLE         top

         /home     /etc/auto.home

       This will generate two mountpoints for /home and /mnt and install
       direct mount triggers for each entry in the direct mount map  All accesses to /home will lead to the consultation
       of the map in /etc/auto.home and all accesses to /mnt will
       consult the NIS map  All accesses to paths in the map will trigger mounts when they are accessed and the Name
       Service Switch configuration will be used to locate the source of
       the map

       To avoid making edits to @mapdir@/auto.master,
       @mapdir@/auto.master.d may be used.  Files in that directory must
       have a ".autofs" suffix, e.g.
       @mapdir@/auto.master.d/extra.autofs.  Such files contain lines of
       the same format as the auto.master file, e.g.

         /foo    /etc/

SEE ALSO         top

       automount(8), autofs(5), autofs(8), autofs.conf(5),

AUTHOR         top

       This manual page was written by Christoph Lameter
       <>, for the Debian GNU/Linux system. Edited by
       <> and Ian Kent <> .

COLOPHON         top

       This page is part of the autofs (automount) project.  Information
       about the project can be found at ⟨⟩.  If
       you have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-07-07.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

                               11 Apr 2006                AUTO.MASTER(5)

Pages that refer to this page: autofs(5)autofs.conf(5)autofs_ldap_auth.conf(5)autofs(8)automount(8)