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

     amd - automatically mount file systems

     amd [-nprv] [-a mount_point] [-C cluster] [-c duration] [-D option]
	 [-d domain] [-k kernel-arch] [-l logfile] [-t interval.interval]
	 [-w interval] [-x log-option] [-y YP-domain]
	 [directory mapname [-map-options]] ...

     amd is a daemon that automatically mounts filesystems whenever a file or
     directory within that filesystem is accessed.  Filesystems are
     automatically unmounted when they appear to be quiescent.

     amd 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 filesystem
     information and some mount options for the given filesystem.

     The options are as follows:

     -a mount_point
	     Specify an alternative location for the real mount points.	 The
	     default is /tmp_mnt.

     -C cluster
	     Specify an alternative cluster name.  The default is the system
	     domain name.  This variable is available inside the configuration
	     file as ${cluster}.

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

     -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.

     -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, the log messages will be sent to
	     the system log daemon by syslog(3).

     -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.

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

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

     -t interval.interval
	     Specify the interval, in tenths of a second, between NFS/RPC/UDP
	     retries.  The default is 0.8 seconds.  The second value alters
	     the retransmit counter.  Useful defaults are supplied if either
	     or both values are missing.

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

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

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

     -y YP-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.  This variable is
	     available inside the configuration file as ${domain}.

     /a	   directory under which filesystems are dynamically mounted

     hostname(1), amq(8), mount(8), umount(8)

     Amd - The 4.4 BSD Automounter, available by running ``info amd''

     The amd utility first appeared in 4.4BSD.

     Jan-Simon Pendry <>, Department of Computing, Imperial
     College, London, UK.

     Some care may be required when creating a mount map.

     Symbolic links on an NFS filesystem 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.  A large improvement
     in real-time performance could be gained by adding a cache somewhere.
     Replacing symlink(2) 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

OpenBSD 4.9			August 12, 2009			   OpenBSD 4.9

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