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) pro‐
       gram is run. Each line describes a mount point and refers to an aut‐
       ofs 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 au‐
       tomounter 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 con‐
       figuration 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 it‐
       self 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 mas‐
       ter 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 au‐
              tomounts. 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 umounted.

              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

              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 ignored.

              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 amd.

              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 line.

              -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 configuration.

              --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

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

       NOTE: mounts done from a hosts map will be mounted with the "no‐
       suid,nodev" options unless overridden by explicitly specifying the
       "suid", "dev" options in the master map 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 automountInforma‐
              tion attribute contains the information used by the auto‐
              mounter. 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 specifi‐
              cation 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 con‐
              taining 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

       If this file exists it will be used to establish whether TLS or au‐
       thentication 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 Au‐
       thority certificate must be set within the LDAP client configuration
       in order to validate the server certificate. If, in addition, a cer‐
       tified connection is to be used then the client certificate and pri‐
       vate key file locations must also be configured within the LDAP

       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 Author‐
       ity 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 information.

       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
       2020-09-18.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-25.)  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)