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

NAME
     amd - automatically mount file systems

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

DESCRIPTION
     amd is a daemon that automatically mounts filesystems whenever a file or
     directory within that filesystem is accessed.  Filesystems are automati-
     cally 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 filesystem infor-
     mation and some mount options for the given filesystem.

     The options are as follows:

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

     -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).

     -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.

     -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 values alters
             the retransmit counter.  Useful defaults are supplied if either
             or both values are missing.

     -v      Version.  Displays version and configuration information on stan-


             dard error.

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

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

     -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.

     -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.

FILES
     /a    directory under which filesystems are dynamically mounted

CAVEATS
     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 symlinks(2) with a suitable incarnation of the auto-mounter re-
     sults 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
     hostname(1), amq(8), fsinfo(8), mk-amd-map(8), mount(8), umount(8)

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

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

HISTORY
     The amd utility first appeared in 4.4BSD.

OpenBSD 3.0                     April 19, 1994                               2
