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 interval.interval ]
[ -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
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 have become 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.
In the first form depicted above, amd will print a short help string.
In the second form, if no options are specified, or 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 /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 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 refereed to by ${rhost} is
normalized 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
compatibility 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. 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 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
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 options
Specify run-time logging options. The options are a comma
separated 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 strings 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.
-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
available 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 improves amd’s
performance, 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
/a directory under which filesystems 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 filesystem can be incredibly inefficient. In
most implementations of NFS, their interpolations are not cached by the
kernel and each time a symlink 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
features.
SEE ALSO
amd.conf(5), amq(8), domainname(1), hostname(1), automount(8),
mount(8), umount(8), mtab(5), syslog(3).
‘‘am-utils’’ info(1) entry.
Linux NFS and Automounter Administration by Erez Zadok, ISBN
0-7821-2739-8, (Sybex, 2001).
http://www.am-utils.org
Amd - The 4.4 BSD Automounter
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.
3 November 1989