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AMD(8)                  FreeBSD System Manager's Manual                 AMD(8)

NAME
     amd - automatically mount file systems

SYNOPSIS
     amd -H
     amd [-F conf_file]
     amd [-nprvHS] [-a mount_point] [-c duration] [-d domain] [-k kernel-arch]
         [-l logfile] [-o op_sys_ver] [-t timeout.retransmit] [-w interval]
         [-x log-option] [-y YP-domain] [-A arch] [-C cluster-name]
         [-D option] [-F conf_file] [-O op_sys_name] [-T tag]
         [directory mapname [-map-options]] ...

DESCRIPTION
     The amd utility is a daemon that automatically mounts file systems
     whenever a file or directory within that file system is accessed.  File
     systems are automatically unmounted when they appear to be quiescent.

     The amd utility operates by attaching itself as an NFS server to each of
     the specified directories.  Lookups within the specified directories are
     handled by amd, which uses the map defined by mapname to determine how to
     resolve the lookup.  Generally, this will be a host name, some file
     system information and some mount options for the given file system.

     In the first form depicted above, amd will print a short help string.  In
     the second form, if no options are specified, or if the -F is used, amd
     will read configuration parameters from the file conf_file which defaults
     to /etc/amd.conf.  The last form is described below.

OPTIONS
     -a temporary-directory
             Specify an alternative location for the real mount points.  The
             default is /.amd_mnt.

     -c duration
             Specify a duration, in seconds, that a looked up name remains
             cached when not in use.  The default is 5 minutes.

     -d domain
             Specify the local domain name.  If this option is not given the
             domain name is determined from the hostname.

     -k kernel-arch
             Specifies the kernel architecture.  This is used solely to set
             the ${karch} selector.

     -l logfile
             Specify a logfile in which to record mount and unmount events.
             If logfile is the string ``syslog'', then the log messages will
             be sent to the system log daemon by syslog(3).  The default
             syslog facility used is LOG_DAEMON.  If you wish to change it,
             append its name to the log file name, delimited by a single
             colon.  For example, if logfile is the string ``syslog:local7''
             then amd will log messages via syslog(3) using the LOG_LOCAL7
             facility (if it exists on the system).

     -n      Normalize hostnames.  The name referred to by ${rhost} is
             normalized relative to the host database before being used.  The
             effect is to translate aliases into ``official'' names.

     -o op_sys_ver
             Override the compiled-in version number of the operating system.
             Useful when the built in version is not desired for backward
             compatibility reasons.  For example, if the build in version is
             ``2.5.1'', you can override it to ``5.5.1'', and use older maps
             that were written with the latter in mind.

     -p      Print PID.  Outputs the process ID of amd to standard output
             where it can be saved into a file.

     -r      Restart existing mounts.  The amd utility will scan the mount
             file table to determine which file systems are currently mounted.
             Whenever one of these would have been auto-mounted, amd inherits
             it.

     -t timeout.retransmit
             Specify the NFS timeout interval, in tenths of a second, between
             NFS/RPC retries (for UDP only).  The default is 0.8 seconds.  The
             second value alters the retransmit counter, which defaults to 11
             retransmissions.  Both of these values are used by the kernel to
             communicate with amd.  Useful defaults are supplied if either or
             both values are missing.

             The amd(8) utility relies on the kernel RPC retransmit mechanism
             to trigger mount retries.  The values of these parameters change
             the overall retry interval.  Too long an interval gives poor
             interactive response; too short an interval causes excessive
             retries.

     -v      Version.  Displays version and configuration information on
             standard error.

     -w interval
             Specify an interval, in seconds, between attempts to dismount
             file systems that have exceeded their cached times.  The default
             is 2 minutes.

     -x options
             Specify run-time logging options.  The options are a comma
             separated list chosen from: fatal, error, user, warn, info, map,
             stats, all.

     -y domain
             Specify an alternative NIS domain from which to fetch the NIS
             maps.  The default is the system domain name.  This option is
             ignored if NIS support is not available.

     -A arch
             Specifies the OS architecture.  This is used solely to set the
             ${arch} selector.

     -C cluster-name
             Specify an alternative HP-UX cluster name to use.

     -D option
             Select from a variety of debug options.  Prefixing an option with
             the string ``no'' reverses the effect of that option.  Options
             are cumulative.  The most useful option is ``all''.

             Since -D is only used for debugging other options are not
             documented here: the current supported set of options is listed
             by the -v option and a fuller description is available in the
             program source.

     -F conf_file
             Specify an amd configuration file to use.  See amd.conf(5) for
             description of this file's format.  This configuration file is
             used to specify any options in lieu of typing many of them on the
             command line.  The amd.conf(5) file includes directives for every
             command line option amd has, and many more that are only
             available via the configuration file facility.  The configuration
             file specified by this option is processed after all other
             options had been processed, regardless of the actual location of
             this option on the command line.

     -H      Print help and usage string.

     -O op_sys_name
             Override the compiled-in name of the operating system.  Useful
             when the built in name is not desired for backward compatibility
             reasons.  For example, if the build in name is ``sunos5'', you
             can override it to ``sos5'' and use older maps which were written
             with the latter in mind.

     -S      Do not lock the running executable pages of amd into memory.  To
             improve amd's performance, systems that support the plock(3)
             call, could lock the amd process into memory.  This way there is
             less chance the operating system will schedule, page out, and
             swap the amd process as needed.  This tends to improve amd's
             performance, at the cost of reserving the memory used by the amd
             process (making it unavailable for other processes).  If this
             behavior is not desired, use the -S option.

     -T tag  Specify a tag to use with amd.conf(5).  All map entries tagged
             with tag will be processed.  Map entries that are not tagged are
             always processed.  Map entries that are tagged with a tag other
             than tag will not be processed.

FILES
     /.amd_mnt          directory under which file systems are dynamically
                        mounted

     /etc/amd.conf      default configuration file

CAVEATS
     Some care may be required when creating a mount map.

     Symbolic links on an NFS file system can be incredibly inefficient.  In
     most implementations of NFS, their interpolations are not cached by the
     kernel and each time a symbolic link is encountered during a lookuppn
     translation it costs an RPC call to the NFS server.  It would appear that
     a large improvement in real-time performance could be gained by adding a
     cache somewhere.  Replacing symlinks with a suitable incarnation of the
     auto-mounter results in a large real-time speedup, but also causes a
     large number of process context switches.

     A weird imagination is most useful to gain full advantage of all the
     features.

SEE ALSO
     domainname(1), hostname(1), syslog(3), amd.conf(5), mtab(5), amq(8),
     mount(8), umount(8)

     ``am-utils'' info(1) entry.

     Erez Zadok, Linux NFS and Automounter Administration, Sybex, 2001, ISBN
     0-7821-2739-8.

     http://www.am-utils.org/

     Amd - The 4.4 BSD Automounter.

HISTORY
     The amd utility first appeared in 4.4BSD.

AUTHORS
     Jan-Simon Pendry <jsp@doc.ic.ac.uk>, Department of Computing, Imperial
     College, London, UK.

     Erez Zadok <ezk@cs.sunysb.edu>, Computer Science Department, Stony Brook
     University, Stony Brook, New York, USA.

     Other authors and contributors to am-utils are listed in the AUTHORS file
     distributed with am-utils.

FreeBSD 11.0-PRERELEASE         January 2, 2006        FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | CAVEATS | SEE ALSO | HISTORY | AUTHORS

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