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AUTOMOUNT(8)                System Manager's Manual               AUTOMOUNT(8)



NAME
       automount - automatically mount NFS file systems

SYNOPSIS
       automount [ -mnTv ] [ -D name= value ] [ -f master-file ]
            [ -M mount-directory ] [ -tl duration ]
            [ -tm interval ] [ -tw interval ]
            [ directory   map [ -mount-options ] ] ...

DESCRIPTION
       automount  is  a  daemon that automatically and transparently mounts an
       NFS file system as needed.  It monitors attempts to access  directories
       that  are  associated with an automount map, along with any directories
       or files that reside under them.  When a file is to  be  accessed,  the
       daemon mounts the appropriate NFS file system.  You can assign a map to
       a directory using an entry in a direct automount map, or by  specifying
       an indirect map on the command line.

       The  automount daemon appears to be an NFS server to the kernel.  auto-
       mount uses the map to locate an appropriate NFS file  server,  exported
       file  system,  and  mount options.  It then mounts the file system in a
       temporary location, and creates a symbolic link to the temporary  loca-
       tion.   If the file system is not accessed within an appropriate inter-
       val (five minutes by default), the daemon unmounts the file system  and
       removes  the symbolic link.  If the indicated directory has not already
       been created, the daemon creates it, and then removes it upon exiting.

       Since the name-to-location binding is dynamic, updates to an  automount
       map  are  transparent  to  the  user.  This obviates the need to ``pre-
       mount'' shared file systems for applications that have  ``hard  coded''
       references to files.

       If  the  directory  argument is a pathname, the map argument must be an
       indirect map.  In an indirect map the key for each entry  is  a  simple
       name  that  represents a symbolic link within directory to an NFS mount
       point.

       If the directory argument is `/-', the  map  that  follows  must  be  a
       direct  map.   A  direct map is not associated with a single directory.
       Instead, the key for each entry is a full  pathname  that  will  itself
       appear to be a symbolic link to an NFS mount point.

       A  map  can  be a file or a Network Information Service (NIS) map; if a
       file, the map argument must be a full pathname.

       The -mount-options argument, when supplied, is a  comma-separated  list
       of mount(8) options, preceded by a `-'.  If these options are supplied,
       they become the default mount options  for  all  entries  in  the  map.
       Mount options provided within a map entry override these defaults.

OPTIONS
       -m     Suppress  initialization  of  directory-map  pairs listed in the
              auto.master NIS database.

       -n     Disable dynamic mounts.  With this  option,  references  through
              the automount daemon only succeed when the target filesystem has
              been previously mounted.   This  can  be  used  to  prevent  NFS
              servers from cross-mounting each other.

       -T     Trace.  Expand each NFS call and display it on the standard out-
              put.

       -v     Verbose.  Log status and/or warning messages to the console.

       -D envar=value
              Assign value to the indicated automount (environment) variable.

       -f master-file
              Read a local file for initialization, ahead of  the  auto.master
              NIS map.

       -M mount-directory
              Mount  temporary file systems in the named directory, instead of
              /tmp_mnt.

       -tl duration
              Specify a duration, in seconds, that a file system is to  remain
              mounted when not in use.  The default is 5 minutes.

       -tm interval
              Specify  an  interval,  in  seconds, between attempts to mount a
              filesystem. The default is 30 seconds.

       -tw interval
              Specify an interval, in seconds,  between  attempts  to  unmount
              filesystems  that have exceeded their cached times.  The default
              is 1 minute.

ENVIRONMENT
       Environment variables  can  be  used  within  an  automount  map.   For
       instance,  if $HOME appeared within a map, automount would expand it to
       its current value for the HOME  variable.   Environment  variables  are
       expanded only for the automounter's environment -- not for the environ-
       ment of a user using the automounter's services.

       The special reference to $ARCH expands to the output of arch (1).  This
       can  be useful in creating a map entry for mounting executables using a
       server's export pathname that varies according to the  architecture  of
       the client reading the map.

       If  a  reference needs to be protected from affixed characters, you can
       surround the variable name with curly braces.

USAGE
   Map Entry Format
       A simple map entry (mapping) takes the form:

              key   [ -mount-options ] location ...

       where key is the full pathname of the directory to mount when used in a
       direct  map,  or  simple  name  in an indirect map.  mount-options is a
       comma-separated list of mount options, and location specifies a  remote
       filesystem  from  which  the  directory  may be mounted.  In the simple
       case, location takes the form:

              hostname:pathname

   Replicated Filesystems
       Multiple location fields can  be  specified  for  replicated  read-only
       filesystems,  in  which  case  automount sends multiple mount requests;
       automount mounts the file system from the first host  that  replies  to
       the mount request.  This request is first made to the local net or sub-
       net.  If there is no response, any connected server may respond.  Since
       automount  does not monitor the status of the server while the filesys-
       tem is mounted it will not use another location in the list if the cur-
       rently mounted server crashes.  This support for replicated filesystems
       is available only at mount time.

       If each location in the list shares the same  pathname  then  a  single
       location may be used with a comma-separated list of hostnames.

              hostname,hostname...:pathname

   Sharing Mounts
       If location is specified in the form:

              hostname:pathname:subdir

       hostname is the name of the server from which to mount the file system,
       pathname is the pathname of the directory to mount,  and  subdir,  when
       supplied,  is  the name of a subdirectory to which the symbolic link is
       made.  This can be used  to  prevent  duplicate  mounts  when  multiple
       directories in the same remote file system may be accessed.  With a map
       for /home such as:

              able homeboy:/home/homeboy:able
              baker     homeboy:/home/homeboy:baker

       and a user attempting to access a file in /home/able, automount  mounts
       homeboy:/home/homeboy, but creates a symbolic link called /home/able to
       the able subdirectory in the temporarily-mounted filesystem.  If a user
       immediately tries to access a file in /home/baker, automount needs only
       to create a symbolic  link  that  points  to  the  baker  subdirectory;
       /home/homeboy is already mounted.

       With the following map:

              able homeboy:/home/homeboy/able
              baker     homeboy:/home/homeboy/baker

       automount would have to mount the filesystem twice.

   Comments and Quoting
       A  mapping  can be continued across input lines by escaping the NEWLINE
       with a backslash.  Comments begin with a # and end  at  the  subsequent
       NEWLINE.

       Characters  that  have special significance to the automount map parser
       may be protected either with double quotes (") or by  escaping  with  a
       backslash  (\).  Pathnames with embedded whitespace, colons (:) or dol-
       lar ($) should be protected.

   Directory Pattern Matching
       The `&&' character is expanded to the value of the  key  field  for  the
       entry in which it occurs.   In this case:

              able homeboy:/home/homeboy:&&

       the && expands to able.

       The `*' character, when supplied as the key field, is recognized as the
       catch-all entry.  Such an entry will be used if any previous entry  has
       not  successfully matched the key being searched for.  For instance, if
       the following entry appeared in the indirect map for /home:

              *    &&:/home/&&

       this would allow automatic mounts in /home of any  remote  file  system
       whose location could be specified as:

              hostname:/home/hostname

   Multiple Mounts
       A multiple mount entry takes the form:

              key [ /[mountpoint [ -mount-options ] location ...  ] ...

       The  initial  /  within  the  `/[mountpoint]' is required; the optional
       mountpoint is taken as a pathname relative to the  destination  of  the
       symbolic  link  for  key.  If mountpoint is omitted in the first occur-
       rence, a mountpoint of / is implied.

       Given the direct map entry:

       /arch/src   \
            /                   -ro,intr       arch:/arch/src           alt:/arch/src   \
            /1.0                -ro,intr       alt:/arch/src/1.0        arch:/arch/src/1.0   \
            /1.0/man  -ro,intr       arch:/arch/src/1.0/man   alt:/arch/src/1.0/man

       automount  would  automatically  mount  /arch/src,  /arch/src/1.0   and
       /arch/src/1.0/man,  as  needed, from either arch or alt, whichever host
       responded first.  If  the  mounts  are  hierarchically  related  mounts
       closer  to  the root must appear before submounts.  All the mounts of a
       multiple  mount  entry  will  occur  together  and  will  be  unmounted
       together.   This  is  important if the filesystems reference each other
       with relative symbolic links.  Multiple mount entries can be used  both
       in direct maps and in indirect maps.

   Included Maps
       The  contents of another map can be included within a map with an entry
       of the form:

              +mapname

       mapname can either be a filename, or the name of an NIS map, or one  of
       the special maps described below.  If the key being searched for is not
       located in an included map, the search continues with the next entry.

   Special Maps
       There are two special maps currently available: -hosts, and -null.  The
       -hosts  map  uses the NIS hosts.byname map to locate a remote host when
       the hostname is specified.  This map specifies mounts of  all  exported
       file  systems  from any host.  For instance, if the following automount
       command is already in effect:

              automount  /net  -hosts

       then a reference to /net/hermes/usr would initiate an  automatic  mount
       of all file systems from hermes that automount can mount; references to
       a directory under /net/hermes will refer to the corresponding directory
       relative to hermes root.

       The  -null  map, when indicated on the command line, cancels any subse-
       quent map for the directory indicated.  It can be used to cancel a  map
       given  in  auto.master  or for a mount point specified as an entry in a
       direct map.

   Configuration and the auto.master Map
       automount normally consults the auto.master NIS configuration map for a
       list  of  initial automount maps, and sets up automatic mounts for them
       in addition to those given on the command line.  If there are  duplica-
       tions,  the command-line arguments take precedence over a local -f mas-
       ter map and they both take precedence  over  an  NIS  auto.master  map.
       This  configuration  database  contains arguments to the automount com-
       mand, rather than mappings; unless -f is in effect, automount does  not
       look for an auto.master file on the local host.

       Maps  given  on the command line, or those given in a local auto.master
       file specified with -f override those in the NIS auto.master map.   For
       instance, given the command:

              automount -f  /etc/auto.master /home -null   /-  etc/auto.direct

       and a file named /etc/auto.master that contains:

              /home   auto.home

       automount would ignore /home entry in /etc/auto.master.

FILES
       /tmp_mnt            directory  under  which filesystems are dynamically
                           mounted

SEE ALSO
       df(1V), ls(1V), stat(2V), passwd(5), mount(8)

NOTES
       The -hosts map must mount all the exported filesystems from  a  server.
       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.

       When  it  receives  signal  number  1,  SIGHUP,  automount  rereads the
       /etc/mtab file to update its internal record of currently-mounted  file
       systems.   If  a  file  system mounted with automount is unmounted by a
       umount command, automount should be forced to reread the file.

       An ls(1V) listing of the entries in the directory for an  indirect  map
       shows  only the symbolic links for currently mounted filesystems.  This
       restriction is intended to avoid unnecessary mounts as a side effect of
       programs that read the directory and stat(2V) each of the names.

       Mount  points  for  a  single  automounter  must  not be hierarchically
       related.  automount will not allow an automount mount point to be  cre-
       ated within an automounted filesystem.

       automount  must  not  be  terminated with the SIGKILL signal (kill -9).
       Without an opportunity to unmount itself, the  automount  mount  points
       will  appear  to  the  kernel to belong to a non-responding NFS server.
       The recommended way to  terminate  automount  services  is  to  send  a
       SIGTERM  (kill  -15) signal to the daemon.  This allows the automounter
       to catch the signal and unmount not only its daemon but also any mounts
       in /tmp_mnt.  Mounts in /tmp_mnt that are busy will not be unmounted.

       Since  each  direct map entry results in a separate mount for the mount
       daemon such maps should be kept short.  Entries added to a  direct  map
       will have no effect until the automounter is restarted.

       Entries  in  both direct and indirect maps can be modified at any time.
       The new information will be used when automount next uses the map entry
       to do a mount.  automount does not cache map entries.

       The  Network Information Service (NIS) was formerly known as Sun Yellow
       Pages (YP).  The functionality of the two remains the  same;  only  the
       name has changed.

BUGS
       The bg mount option is not recognized by the automounter.

       Since  automount  is  single-threaded, any request that is delayed by a
       slow or non-responding NFS server will delay all  subsequent  automatic
       mount requests until it completes.

       Programs  that  read  /etc/mtab  and then touch files that reside under
       automatic mount points will introduce further entries to the file.

       Automatically-mounted file systems are mounted with type  ignore;  they
       do not appear in the output of either mount(8), or df(1V).



                                20 January 1990                   AUTOMOUNT(8)