automount.8nfs

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH automount 8nfs
.SH Name
automount \- automatically and transparently mounts and unmounts NFS file systems
.SH Syntax
.B /usr/etc/automount
[
.B \-mnTv
.\" v
]
[
.I \-D name=
.I value
]
[
.B \-f 
.I master-file
]
.br
[
.B \-M 
.I mount-directory
]
[
.B \-tl
.I duration 
.\" .I sub-options
]
[
.B \-tm
.I interval
]
[
.B \-tw
.I interval  
]
.br
[
.I directory mapname
[
.B \-
.I mount-options
]]
.SH Description
The 
.PN automount 
.NXR "automount command"
command  
transparently mounts and
unmounts NFS file systems on an as-needed basis.  
It is useful for mounting file systems and directories that are
needed only occasionally, and
it provides an alternative to using
.PN /etc/fstab
.\" .NXR "automount command" "/etc/fstab file"
.\" .NXR "automount command" "/etc/rc.local file"
for NFS mounting file systems on client machines.
.PP
The 
.PN automount
program can be started from the
.PN /etc/rc.local
file or the command line. 
.\".NXR "automount command" "and /etc/fstab file"
.\".NXR "automount command" "and /etc/rc.local file"
The daemon forked by the
.PN automount
program sleeps until a user attempts to access a directory that is
associated with an 
.PN aautomount 
map.
The daemon then consults the appropriate map and mounts the NFS
file system.  If the indicated directory has not already been created,
the daemon creates it and removes it after automatic 
.PN unmount .
.PP
Local 
.PN automount 
maps are typically located in the
.PN /etc
directory but can be placed in any directory. 
You also can use the Yellow Pages Service to distribute
.PN automount
maps. 
The maps indicate where to find the file system to be
mounted, the local mount point, and mount options.  After a specified 
period of inactivity on a file system, 5 minutes by default, the
.PN automount
daemon unmounts that file system.
.PP
An individual automount map is either local or served by the Yellow
Pages.  A system, however,
can use both local and Yellow Pages automount maps.
When a map is referenced, the
.PN automount
program first looks for the designated 
.I mapname 
locally.  If it 
cannot find the 
.I mapname 
locally, it looks for a Yellow
Pages map by that name.
The names of the maps are passed to  
.PN automount
from the command line, or from a master map. 
.PP
If the command line
and the master 
map contain contradictory arguments, those on the command line take precedence.
.PP
By default, the daemon mounts the remote file system under the directory
.PN /tmp_mnt
and creates a symbolic link between the requested and the actual
mount points.
.SS Maps
Conventionally, 
.PN automount 
maps are files that are located in the
.PN /etc 
directory with names that have the prefix
.PN auto .  
.NXR "automount maps"
They indicate which remote file systems to mount,
where to mount them, and which options to use.  
.ne 6
.SS "\fIThe Master Map"
The 
.PN automount
program can consult a master map, which contains entries that point to other
maps that can be either direct or indirect.  If Yellow Pages is running,
.PN automount
checks for the presence of a YP map named 
.PN auto.master .
You are not required to run YP or have an 
.PN auto.master
map.  A master map can also be a file whose location is specified with 
the 
.PN \-f 
command line option.  
.PP
The master map provides 
.PN automount 
with a list of maps, and with arguments that pertain
to each of the maps. 
Each line in the
master map has the following syntax:
.PP
.I "mount-point   map  [mount-options]"
.PP
.IP \(bu 4
.I Mount-point
is the full pathname of a local directory if the
.I map
argument is the name of an indirect map or the name of a special map.
If the
.I map 
argument is the name of a direct map, the dummy directory ``/-'' is 
specified as the 
.I mount-point.
.IP \(bu 4
.I Map
is the name of the map the automount command uses to find the mount points
and locations.  This can either be a filename, a YP map name, or a
special map name.
.IP \(bu 4
.I Mount-options
is a list of options used to regulate the mounting of entries listed in
.I map.
.ne 6
.SS "\fIDirect Maps"
Direct maps specify which remote file systems to mount locally and what
the local mount points are. They do not point to other maps. They also
can specify mount options. 
Direct maps have the following syntax:
.PP
.I "key   [mount-options]   location"
.PP
.IP \(bu 4
.I Key
is the full pathname of the mount point.
.IP \(bu 4
.I Mount-options
are the options for this specific mount. When present, these options  
override any mount options specified on the command line
or in the master map.
.IP \(bu 4
.I Location
is the location of the resource being mounted, specified as:
.I server:pathname.  
Multiple 
.I location
fields can be specified, in which case 
.PN automount
sends multiple mount requests and mounts from the first server to 
respond.
.ne 6
.SS "\fIIndirect Maps"
Indirect maps have the same format as direct maps.
The only difference between a direct and an indirect map is that the key
in a direct map is a full pathname, whereas the key in an indirect
map is a simple name that does not begin with a slash.  (Remember that
the indirect map as a whole has been associated with a directory
specified in the master map or on the command line.  The entries in an
indirect map list subdirectories that are individually mounted within
the directory associated with the map.)
.\" 
.\" (the next section is commented out from the original version
.\"  of this manpage due to the fact that it seemed curiously misleading
.\"
.\".PP
.\" The maps contain entries in the following format.  While multiple locations
.\" for a particular \fIbasename\fR can be specified, they
.\"should only be used for read-only file systems.
.\".EX
.\"[\fIbasename\fR [\fI\-mount-options\fR][\fIlocation1\fR][\fIlocation2\fR]...
.\".EE
.\"The \fIbasename\fR field specifies a subdirectory within the 
.\".I directory
.\"designated in the 
.\".PN automount 
.\"command line.  
.\"The \fI\-mount-options\fR tell the 
.\".PN automount 
.\"program what parameters and access restrictions apply to that mount.  
.\"See mount(8nfs) for more information.
.\".PP
.\"Each \fIlocation\fR field indicates where the file system resides on
.\"the remote host, and has the following format:
.\"Maps are considered either direct or indirect depending
.\"on how the \fIbasename\fR field is specified.
.\"In a direct map the \fIbasename\fR is a full pathname.
.\"In an indirect map the \fIbasename\fR is a simple name.  
.\"The rest of the required information about where the remote file system
.\"is located is provided either on the command line or in another map.
.\"The rest of the information that 
.\".PN automount
.\"requires about
.\"the remote file system location is provided either on the command line
.\"or in another map.
.\".EX
.\"\fIhost:remote-pathname[:subdirectory]
.\".EE
.\"The \fIhost\fR field specifies the remote host from which
.\"to mount the designated file system.  The \fIremote-pathname\fR is 
.\"the absolute pathname of a file system or subtree of a file system that
.\"is exported by \fIhost\fR.  
.\".PP
.\"If you specify more than one location for a file system, the 
.\".PN automount 
.\"program broadcasts a mount request to all specified hosts.
.\"The first to respond gets mounted.
.\".PP
.\"The \fIsubdirectory\fR field is optional.
.\"When supplied, it indicates the subdirectory within the 
.\"remote file system to which you want \fIbasename\fR linked.  
.\"Specifying subdirectories allows mount points to be shared.
.\"Rather than creating a symbolic link directly to the mount point,
.\".PN automount
.\"creates a symbolic link to the specified subdirectory.  One 
.\"mount point can have multiple symbolic links to subdirectories
.\"within the mounted file system.
.ne 6
.SS "\fISpecial Maps"
The 
.PN \-hosts
map is a special 
.PN automount 
map that is used to access all directories
exported by a server to a client.  
.PP
The following command allows a client to access directories 
that are exported from any host in its
.PN /etc/hosts
file, the Yellow Pages hosts database, or the BIND database.
.EX 
# \f(CBautomount /net \-hosts\f(CW
.EE
.NXR "automount maps" "and Yellow Pages"
.PP
For example, suppose that 
.PN hera 
and 
.PN sheba