FreeBSD Man Pages

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] [-C cluster-name] [-D option]
	 [-F conf_file] [-O op_sys_name] [-T tag] [directory mapname
	 [-map-options]] ...

DESCRIPTION

     Amd is a daemon that automatically mounts file systems whenever a file or
     directory within that file system is accessed.  File systems are automat-
     ically unmounted when they appear to be quiescent.

     Amd operates by attaching itself as an NFS server to each of the speci-
     fied 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 infor-
     mation 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, 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 mes-
	     sages 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

     -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 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.

	     Amd 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.

     -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 file includes directives for every
	     command line option amd has, and many more that are only avail-
	     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.  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 fea-
     tures.

SEE ALSO

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

     Amd - The 4.4 BSD Automounter.

     http://www.cs.columbia.edu/~ezk/am-utils/

AUTHORS

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

     Erez Zadok <ezk@cs.columbia.edu>, Department of Computer Science,
     Columbia University, New York, USA.

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

SPONSORED LINKS