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AMD(8)			  BSD 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 when‐
     ever a file or directory within that file system is accessed.  File sys‐
     tems 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 sys‐
     tem 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 normal‐
	     ized 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 com‐
	     patibility 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 stan‐
	     dard 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 sepa‐
	     rated 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 docu‐
	     mented here: the current supported set of options is listed by
	     the -v option and a fuller description is available in the pro‐
	     gram 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 avail‐
	     able 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 per‐
	     formance, 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 fea‐
     tures.

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.

BSD				January 2, 2006				   BSD
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