autofs.conf(5) — Linux manual page


AUTOFS.CONF(5)             File Formats Manual            AUTOFS.CONF(5)

NAME         top

       autofs.conf - autofs configuration

DESCRIPTION         top

       Configuration settings used by automount(8) may be changed in the
       configuration file @mapdir@/autofs.conf.

       This file contains two primary sections, autofs and amd.

       Configuration entries may be present at the beginning of the
       configuration file without a section header and are implicitly
       included as part of the autofs section.

       Each section name is enclosed in square brackets with spaces
       between the brackets and the section name. The amd section may be
       followed by further sections, named by the top level mount point
       path, that contain per mount configuration settings.


       Configuration settings available are:

       +.B open_file_limit
     +Set the maximum number of open files. Note there may
              be other limits +within the system that prevent this from
              being set, systemd for example +may need a setting in the
              unit file to increase its default. The autofs +default is
              20480.  +.TP timeout
              Sets the default mount timeout in seconds. The internal
              program default is 10 minutes, but the default installed
              configuration overrides this and sets the timeout to 5
              minutes to be consistent with earlier autofs releases.

              Sets the default maximum number of retries (actaul
              iterations is half this, each is delayed by 2 seconds
              before retrying) waiting for the master map to become
              available if it cannot be read at program start (program
              default 10, then continue). This can be longer if the map
              source itself waits for availability (such as sss).

              Set the default timeout for caching failed key lookups
              (program default 60). If the equivalent command line
              option is given it will override this setting.

              Set the default timeout for using cached map entries
              (program default 120). If the equivalent command line
              option is given it will override this setting.

              Use the verbose flag when spawning mount(8), and log some
              process info about the requestor and its parent (program
              default "no").

              Set the default time to wait for a response from a spawned
              mount(8) before sending it a SIGTERM. Note that we still
              need to wait for the RPC layer to timeout before the sub-
              process exits so this isn't ideal but it is the best we
              can do. The default is to wait until mount(8) returns
              without intervention.

              Set the default time to wait for a response from a spawned
              umount(8) before sending it a SIGTERM. Note that we still
              need to wait for the RPC layer to timeout before the sub-
              process exits so this isn't ideal but it is the best we
              can do.

              Maps are browsable by default (program default "yes").

              Set the default protocol that mount.nfs(8) uses when
              performing a mount (program default 3). Autofs needs to
              know the default NFS protocol that mount.nfs(8) uses so it
              can do special case handling for its availability probe
              for different NFS protocols. Since we can't identify this
              default automatically we need to set it in the autofs

              Determine whether global options, given on the command
              line or per mount in the master map, are appended to map
              entry options or if the map entry options replace the
              global options (program default "yes", append options).

              set default log level "none", "verbose" or "debug"
              (program default "none").

              override the use of a prefix with standard environment
              variables when a program map is executed. Since program
              maps are run as the privileged user setting these standard
              environment variables opens automount(8) to potential user
              privilege escalation when the program map is written in a
              language that can load components from, for example, a
              user home directory (program default "no").

              This configuration option may be used to change the number
              of hash table slots (default 1024).

              This configuration option affects the overhead of
              searching the map entry cache for map entries when there
              are a large number of entries.  It affects the number of
              entries that must be looked at to locate a map entry in
              the map entry cache. For example, the default of 1024 and
              a direct map with 8000 entries would result in each slot
              containing an average of 8 entries, which should be

              However, if excessive CPU usage is observed during
              automount lookups increasing this option can reduce the
              CPU overhead considerably because it reduces the length of
              the search chains.

              Note that the number of entries in a map doesn't
              necessarily relate to the number of entries used in the
              map entry cache.

              There are two distinct cases where the map hash table can
              make a significant difference, direct maps and indirect
              maps that use the "browse" option.

              For indirect maps that do not use the "browse" option
              entries are added to the map entry cache at lookup so the
              number of active cache entries, in this case, is usually
              much less than the number of entries in the map. In this
              last case it would be unusual for the map entry cache to
              grow large enough to warrant increasing the default before
              an event that cleans stale entries, a map re-read for

              NFS mounts where the host name resolves to more than one
              IP address are probed for availability and to establish
              the order in which mounts to them should be tried. To
              ensure that mount attempts are made only to hosts that are
              responding and are tried in the order of hosts with the
              quickest response the IP address of the host needs to be
              used for the mount.

              If it is necessary to use the hostname given in the map
              entry for the mount regardless, then set this option to

              Be aware that if this is done there is no defense against
              the host name resolving to one that isn't responding and
              while the number of attempts at a successful mount will
              correspond to the number of addresses the host name
              resolves to the order will also not correspond to fastest
              responding hosts.

              The original request to add this log message needed it to
              be unconditional.  That produces, IMHO, unnecessary noise
              in the log so a configuration option has been added to
              provide the ability to turn it off. The default is "no" to
              maintain the current behaviour.

              An option to enable the use of autofs pseudo option
              "disable". This option is used as a hint to user space
              that the mount entry should be ommitted from mount table
              listings. The default is "no" to avoid unexpected changes
              in behaviour and so is an opt-in setting.

              Set the time to wait and retry if sssd is unable to read
              the master map at program start. Program default is 0
              (don't wait) or 10 if sss supports returning EHSTDOWN when
              the provider isn't available.

              If the sss library supports returning EHOSTDOWN when the
              provider is down then this value is how long to wait
              between retries reading the master map.  When reading
              dependent maps or looking up a map key this value is
              multiplied by the number of retries that would be used
              when reading the master map.

              Set whether to use a mount request log id so that log
              entries for specific mount requests can be easily
              identified in logs that have multiple concurrent requests.
              Default is don't use mount request log ids.

   LDAP Configuration
       Configuration settings available are:

              Set the network response timeout (default 8).  Set timeout
              value for the synchronous API calls. The default is the
              LDAP library default of an infinite timeout.

              Set the network response timeout (default 8).

              A space separated list of server uris of the form
              <proto>://<server>[/] where <proto> can be ldap or ldaps.
              The option can be given multiple times.  Map entries that
              include a server name override this option and it is then
              not used. Default is an empty list in which case either
              the server given in a map entry or the LDAP configured
              default is used. This uri list is read at startup and
              whenever the daemon receives a HUP signal.

              This configuration option can also be used to request
              autofs lookup SRV RRs for a domain of the form
              <proto>:///[<domain dn>]. Note that a trailing "/" is not
              allowed when using this form. If the domain dn is not
              specified the dns domain name (if any) is used to
              construct the domain dn for the SRV RR lookup. The server
              list returned from an SRV RR lookup is refreshed according
              to the minimum ttl found in the SRV RR records or after
              one hour, whichever is less.

              The base dn to use when searching for amap base dn. This
              entry may be given multiple times and each will be checked
              for a map base dn in the order they occur in the
              configuration. The search base list is read at startup and
              whenever the daemon recieves a HUP signal.

              The map object class. In the nisMap schema this
              corresponds to the class nisMap and in the automountMap
              schema it corresponds to the class automountMap.

              The map entry object class. In the nisMap schema this
              corresponds to the class nisObject and in the automountMap
              schema it corresponds to the class automount.

              The attribute used to identify the name of the map to
              which this entry belongs.  In the nisMap schema this
              corresponds to the attribute nisMapName and in the
              automountMap schema it corresponds to the attribute ou or

              The attribute used to identify a map key. In the nisMap
              schema this corresponds to the attribute cn and in the
              automountMap schema it corresponds to the attribute

              The attribute used to identify the value of the map entry.
              In the nisMap schema this corresponds to the attribute
              nisMapEntry and in the automountMap schema it corresponds
              to the attribute automountInformation.

       NOTE:  It is essential that entries use class and attribute in a
              consistent manner for correct operation of autofs. For
              example mixing cn and automountKey attributes in automount
              schema will not work as expected.

              This configuration option may be used to specify an
              alternate location for the ldap authentication
              configuration file. See autofs_ldap_auth.conf(5) for more


       A number of the amd configuration options are not used by autofs,
       some because they are not relevant within autofs, some because
       they are done differently in autofs and others that are not yet

       Since mount_type is always autofs (because there's no user space
       NFS server) the configuration entries relating to that aren't
       used.  Also, server availability is done differently within
       autofs so the options that relate to the amd server monitoring
       sub-system are also not used.

       These options are mount_type, auto_attrcache, portmap_program,
       nfs_vers_ping, nfs_allow_any_interface, nfs_allow_insecure_port,
       nfs_proto, nfs_retransmit_counter, nfs_retransmit_counter_udp,
       nfs_retransmit_counter_tcp, nfs_retransmit_counter_toplvl,
       nfs_retry_interval, nfs_retry_interval_udp,
       nfs_retry_interval_tcp, nfs_retry_interval_toplvl and nfs_vers.

       Other options that are not used within the autofs implementation:

       log_file, truncate_log
              sends its output to syslog so an alternate log file (or
              truncating the log) can't be used.

              There's no corresponding option for this within autofs.

       use_tcpwrappers, show_statfs_entries
              There's no user space NFS server to control access to so
              this option isn't relevant. The show_statfs_entries can't
              be implemented for the same reason.

              There's no user space NFS server and autofs avoids using
              file based mtab whenever possible.

              Sun map format is handled by autofs itself.

       plock, show_statfs_entries, preferred_amq_port
              Are not supported by autofs.

       ldap_cache_maxmem, ldap_cache_seconds
              External ldap caching is not used by autofs.

              autofs always attempts to use the highest available ldap
              protocol version.

       cache_duration, map_reload_interval, map_options
              The map   entry cache is continually updated and stale
              entries cleaned on re-load, which is done when map changes
              are detected so these configuration entries are not used
              by autofs. An exception to this is the case where the map
              is large. In this case it may be necessary to read the
              whole map at startup even if browsing is not enabled.
              Adding the cache:=all option to map_options can be used to
              for this.

              This is not used within autofs. This configuration option
              was only used in the amd user space server code and is not
              relevant within autofs.

       Options that are handled differently within autofs:

              To specify a pid file name a command line option must be
              used on startup.

              Program version and feature information is obtained by
              using the automount command line option "-V".

       debug_options ,  log_options
              autofs has somewhat more limited logging and debug logging
              options.  When the log_options options is encountered it
              is converted to the nearest matching autofs logging
              option. Since the configuration option debug_options would
              be handled the same way it is ignored.

              This option has no sensible meaning within autofs because
              autofs always tries to re-connect to existing mounts.
              While this has its own set of problems not re-connecting
              to existing mounts always results in a non-functional
              automount tree if mounts were busy at the last shutdown
              (as is also the case with amd when using mount_type

              Detaching mounts often causes serious problems for users
              of existing mounts. It is used by autofs in some cases,
              either at the explicit request of the user (with a command
              line or init option) and in some special cases during
              program operation but is avoided whenever possible.

       A number of configuration options are not yet implemented:

              Always a little frustrating, the compiled in map location
              should be used to locate maps but isn't in some cases.
              This requires work within autofs itself and that will
              (obviously) include implementing this configuration option
              for the amd map parser as well.

              Not yet implemented.

              Since autofs always tries to re-connect to mounts left
              mounted from a previous shutdown this is a sensible option
              to implement and that will be done.

              Allow map keys to be shown in directory listings. This
              option can have values of "yes" or "no". The default is
              "no". A variation of this option, "browsable", can be used
              as a pseudo mount option in type "auto" map entries to
              provide browsing functionality in sub-mounts. The amd
              "browsable_dirs = full" option cannot be implemented
              within the current autofs framework and is not supported.

              A timeout is not currently used for program maps but this
              might be implemented in the future.

              The tag option is not implemented within autofs.

       Supported options:

       arch, karch, os, osver
              These options default to what is returned from uname(2)
              and can be overridden if required.

              This option has no default and must be set in the
              configuration if used in maps.

              If not set defaults to the host domain name. This option
              corresponds to the HP_UX cluster name (according to the
              amd source) and is probably not used in Linux but is set

       vendor This option has a default value of "unknown", it must be
              set in the configuration if used in maps.

              Is the base name of the mount tree used for external
              mounts that are sometimes needed by amd maps. Its default
              value is "/a".

              Specifies the autofs map source, such as file, nis, ldap
              etc. and has no default value set.

              This option is used to override /defaults entries within
              maps and can be used to provide different defaults on
              specific machines without having to modify centrally
              managed maps. It is empty by default.

              Colon separated paths to search for maps that are not
              specified as a full path.

              Is equivalent to the autofs timeout option. It is only
              possible to use this with type "auto" mounts due to the
              way the autofs kernel module performs expiry. It takes its
              default value from the autofs internal default of 600

              If set to "yes" autofs will attempt to use bind mounts for
              type "link" entries when possible (default is "yes").

              Allows setting of a domain name other than the system

              Is used to override (or set) the host domain name.

              If set to "yes" then the contents of ${rhost} is
              translated in its official host name.

              If set to "yes" the domain name part of the host is
              stripped when normalizing hostnames. This can be useful
              when using of the same maps in a multiple domain

              This option is set to "yes" by default and will collapse
              multiple unescaped occurrences of "/" to a single "/".

       selectors_in_defaults, selectors_on_default
              This option has a default value of "no". If set to "yes"
              then any defaults entry will be checked for selectors to
              determine the values to be used. selectors_in_defaults is
              the preferred option to use.

              iThis option has no default value. It must be set to the
              base dn that is used for queries if ldap is to be used as
              a map source.

              This option has no default value set. It must be set to
              the URI of the LDAP server to be used for lookups when
              ldap is used as a map source. It may contain a comma or
              space separated list of LDAP URIs.

              Sets the base name used for hesiod map sources.

              This is an additional configuration option for the autofs
              amd format parser implementation.

              There's no simple way to determine what the system default
              filesystem is and am-utils needs to be continually updated
              to do this and can easily get it wrong ayway. So allow it
              to be set in the configuration.

EXAMPLE         top

         [ autofs ]
         timeout = 300
         browse_mode = no

         [ amd ]
         dismount_interval = 300
         map_type = nis
         autofs_use_lofs = no

         [ /expamle/mount ]
         dismount_interval = 60
         map_type = file

SEE ALSO         top

       automount(8), auto.master(5), autofs_ldap_auth.conf(5).

AUTHOR         top

       This manual page was written by 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
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-05-23.)  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

                               23 Jan 2014                AUTOFS.CONF(5)

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