AUTOMOUNT(8)AUTOMOUNT(8)NAMEautonfsmount - automatically mount NFS file systems
SYNOPSISautonfsmount [ -mnT ] [ -tl duration ] [ -tm interval ] [ -tw interval
] [ -a directory ] [ directory mapname [ -mount-options ] ] ...
DESCRIPTIONautonfsmount is a daemon that will automatically and transparently
mount an NFS file system whenever a file or directory within that
system is opened. autonfsmount forks a daemon, which appears to be an
NFS server to the kernel; lookups on the specified directory are
intercepted by this daemon, which uses the map contained in mapname to
determine a server, exported file system, and appropriate mount options
for a given file system. The named map can either be a file on the
local system, a Yellow Pages map or some special "maps" which are
hardwired into autonfsmount itself. directory is a full pathname
starting with a `/'.
When supplied, -mount-options consists of the leading - and a comma-
separated list of mount(8) options; if mount options are specified in
the map, however, those in the map take precedence.
Once mounted, members of the directory are made available using a
symbolic link to the real mount point within a temporary directory.
If directory does not exist, the daemon creates it, and then removes it
automatically when the daemon exits.
Since the name-to-location binding is dynamic, updates to a Yellow
Pages map are transparent to the user. This obviates the need to
``pre-mount'' shared file systems for applications that have ``hard
coded'' references to files. It also obviates the need to maintain
records of which hosts must be mounted for what applications.
Maps
autonfsmount looks first for the indicated mapname in a file by that
name. If there is no such file, it looks for a YP map by that name.
An autonfsmount map is composed of a list of mappings, with one mapping
per line. Each mapping is composed of the following fields:
basename [-mount-options] location [...]
where basename is the name of a subdirectory within the directory
specified in the autonfsmount command line (not a relative pathname).
The location field consists of an entry of the form:
host:directory[:subdir]
where host is the name of the host from which to mount the file system,
directory is the pathname of the directory to mount, and subdir, when
supplied, is the name of a subdirectory to which the symbolic link is
made. This can be used to prevent duplicate mounts in cases where
multiple directories in the same remote file system are accessed.
The contents of a YP map can be included within a map by adding an
entry of the form:
+mapname
A mapping can be continued across line breaks using a \ as the last
character before the NEWLINE. Comments begin with a # and end at the
subsequent NEWLINE.
If more than one location is supplied, there is no guarantee as to
which location will be used; the first location to respond to the mount
request gets mounted. The mount-options field can be used to supply
options to the mount(8) command for the mounted file system.
Special Maps
There are two special maps currently available. The -hosts map uses
the Yellow Pages hosts.byname map to locate a remote host when the
hostname is specified as a subdirectory of directory. This map
specifies mounts of all exported file systems from any host. For
instance, if the following autonfsmount command is already in effect:
autonfsmount /net -hosts
then a reference to /net/hermes/usr would initiate an automatic mount
of all file systems from hermes that autonfsmount can mount; references
to a directory under /net/hermes will refer to the corresponding
directory on hermes.
The -fstab special map uses the mounts database (fstab(5)) map to
locate a remote host when the hostname is specified as a subdirectory
of directory. This map specifies mounts of all exported file systems
from any host in the mounts database. The advantage of -fstab over
-hosts is that you can list the available servers and also leverage off
of the mount options available in the familiar fstab(5) format. Note
that for autonfsmount to pick up entries in the mounts database, the
entries must have the fstab(5) "net" option and also must have a mount
point identical to that of autonfsmount. For instance, if the
following autonfsmount command is already in effect:
autonfsmount /Net -fstab
and hermes is in the mounts database as follows:
hermes:/usr /Net nfs rw,net 0 0
then a reference to /Net/hermes/usr would initiate an automatic mount
of all file systems from hermes that autonfsmount can find in the
mounts database; references to a directory under /Net/hermes will refer
to the corresponding directory on hermes.
The -passwd map uses the passwd(5) database to attempt to locate the
home directory of a user. For instance, if the following autonfsmount
command is already in effect:
autonfsmount /homes -passwd
then if the home directory shown in the passwd entry for the user
username has the form /dir/server/username, and server matches the host
system on which that directory resides, references to files in
/homes/username result in the file system containing that directory
being mounted if necessary, and all such references will refer to that
user's home directory.
Configuration
autonfsmount normally consults the auto.master Yellow Pages
configuration database for a list of initial directory to mapname
pairs, and sets up automatic mounts for them in addition to those given
on the command line; if there are duplications, the command-line
arguments take precedence. (Note that this database contains arguments
to the autonfsmount command, rather than mappings, and that
autonfsmount does not look for an auto.master file on the local host.)
OPTIONS-m Suppress initialization of directory-mapname pairs listed in the
auto.master Yellow Pages database.
-n Disable dynamic mounts. With this option, references through
the autonfsmount daemon only succeed when the target file system
has been previously mounted. This can be used to prevent NFS
servers from cross-mounting each other.
-T Trace. Expand each NFS call and display it on the standard
output.
-tl duration
Specify a duration, in seconds, that a looked up name remains
cached when not in use. The default is 5 minutes.
-tm interval
Specify an interval, in seconds, between attempts to mount a
file system. The default is 30 seconds.
-tw interval
Specify an interval, in seconds, between attempts to dismount
file systems that have exceeded their cached times. The default
is 1 minute.
-a directory
Specify an alternate directory for the actual mounts performed
by autonfsmount. The default is /tmp_mnt.
EXAMPLE
tutorial# autonfsmount-m /net -hosts
Provide autonfsmount access to the exported file systems of any host in
the Yellow Pages hosts.byname database, by prefixing the pathname with
/net/hostname/ :
tutorial% ls /net/hermes/usr/src ...
FILES
/tmp_mnt directory under which file systems are dynamically
mounted
SEE ALSOmount(8),netinfo(5),fstab(5)BUGS
Shell filename expansion does not apply to objects not currently
mounted or cached. For instance, in the above example, the command ls
/net/* might not list hermes as a subdirectory of /net. However, the
special map -fstab does not suffer from this bug.
20 January 1988 AUTOMOUNT(8)