AMD(8) OpenBSD System Manager's Manual AMD(8)NAMEamd - automatically mount file systems
SYNOPSISamd [-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]] ...
DESCRIPTIONamd 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}.
FILES
/a directory under which filesystems are dynamically mounted
SEE ALSOhostname(1), amq(8), mount(8), umount(8)
Amd - The 4.4 BSD Automounter, available by running ``info amd''
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.
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 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
features.
OpenBSD 4.9 August 12, 2009 OpenBSD 4.9