There are three types of
automount
maps:
The
automount
maps can be written in a variety of ways. Maps
can be direct or indirect. They can be simple or can use multiple
mounts, shared mounts, replicated file systems, or any combination of
the three. As discussed in
Section C.1,
indirect maps can be written to reduce redundancy by
using substitution characters and pattern matching.
The examples in this section illustrate how the same maps
can be rewritten in a number of ways.
Figure C-1
illustrates an
auto.master
map that points to the
/etc/auto.direct
direct map, the built-in
-hosts
map, and the
/etc/auto.home
indirect map. Each map to which the
auto.master
map points is expanded to show its sample contents.
Note that all of the information contained in the master map
can be specified on the command line. The master map, however, simplifies
organization and administration of
automount.
The following examples show how the
/etc/auto.direct
map in
Figure C-1
can be rewritten using multiple mounts
(Example C-1);
multiple mounts and shared mounts
(Example C-2);
and multiple mounts, shared mounts, and replicated file systems
(Example C-3).
/mnt/mytmp june:/usr/staff/jones/tmp
/mnt/mynotes june:/usr/staff/jones/notes
/usr/arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
/mnt/mytmp june:/usr/staff/jones:tmp
/mnt/mynotes june:/usr/staff/jones:notes
/usr/arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
/mnt/mytmp june:/usr/staff/jones:tmp
/mnt/mynotes june:/usr/staff/jones:notes
/usr/arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
bazel:/src/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
fiesta:/archive/uws\
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
The
/etc/auto.direct
maps in the preceding examples could be
rewritten as indirect maps. If the
/etc/auto.direct
map is rewritten to be an indirect map, the entry pointing to it in the
auto.master
map might read:
/mnt /etc/auto.indirect
Rewritten as a simple indirect map
(/etc/auto.indirect),
the
/etc/auto.direct
map in
Figure C-1
would read as shown in
Example C-4.
mytmp june:/usr/staff/jones/tmp mynotes june:/usr/staff/jones/notes arch -ro chester:/usr/arch
Note that the
key
is a simple pathname.
The following examples illustrate that indirect maps can also be rewritten using multiple mounts (Example C-5); multiple mounts and shared mounts (Example C-6); and multiple mounts, shared mounts, and replicated file systems (Example C-7).
mytmp june:/usr/staff/jones/tmp
mynotes june:/usr/staff/jones/notes
arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
mytmp june:/usr/staff/jones:tmp
mynotes june:/usr/staff/jones:notes
arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
mytmp june:/usr/staff/jones:tmp
mynotes june:/usr/staff/jones:notes
arch / -ro chester:/usr/arch \
/bsd -ro chester:/usr/arch/bsd \
bazel:/src/bsd \
/standards -ro chester:/usr/arch/standards \
/dec/uws -ro chester:/usr/arch/dec/uws \
fiesta:/archive/uws\
/dec/ultrix -ro chester:/usr/arch/dec/ultrix
The
-hosts
map is a built-in map supplied by
automount.
This map allows a client to access directories that
are exported from any host in its
hosts
database. The location
of the
hosts
database that your system uses is determined by the
services running on your system (BIND, NIS, local) and how those services
are specified in the
/etc/svc.conf
file. References to a
particular host name result in all of the file systems that are exported from
that host being mounted on the local system. For example, the following command
results in all of the file systems that are exported from
host1
being mounted on the local system:
#
cd /net/host1
The
/etc/auto.home
map shown in
Figure C-1
is an indirect map that allows users to remote mount their home directories.
It can be rewritten using the ampersand (&) and asterisk (*) substitution
characters.
The following example shows how the
/etc/auto.home
map in
Figure C-1
can be rewritten using ampersands (&):
user1 host1:/usr/staff/& user2 host2:/usr/staff/& user3 host2:/usr/staff/& user4 host2:/usr/staff/& user5 host3:/usr/staff/&
The
automount
daemon
recognizes the following substitution characters, allowing you to
eliminate redundancy within
automount
maps:
Can be used in both direct and indirect maps; however, it is most efficient and easily understood when used in indirect maps.
Can be used in indirect maps only.
Because the ampersand and asterisk are most easily used in indirect maps, this section discusses them in the context of indirect maps only. Recall that lines in indirect maps have the following syntax:
key mount-options location
Whenever the
automount
daemon encounters an ampersand (&) in a
line of an indirect map, it substitutes the
key
in that line for the ampersand (&).
The following example is an indirect map that does not use ampersands:
#key mount-options location # host1 -rw,nosuid host1:/home/host1 host2 -rw,nosuid host2:/home/host2
Using the ampersand (&) as a substitution character, the entries read as follows:
#key mount-options location # host1 -rw,nosuid &:/home/& host2 -rw,nosuid &:/home/&
You can use the asterisk (*) to substitute for lines that are all
formatted similarly. The
automount
daemon uses the asterisk to match any host not listed as a key in
an entry before the asterisk. The following is a typical use of the
asterisk (*):
#key mount-options location # host1 -rw,nosuid &:/home/& host2 -rw,nosuid &:/home/& * -rw,nosuid &:/home/&
Suppose a user enters the following command:
%
ls /home/host5
The
automount
daemon substitutes the host name
(host5)
as the
key.
After it has substituted
host5
for the
key,
it then substitutes
host5
for each of the ampersands in the
location
field as well. The
automount
daemon translates the preceding command into the following:
#key mount-options location # host5 -rw,nosuid host5:/home/host5
Note
The
automountdaemon ignores any entry that follows an asterisk.
You can use the value of an environment variable in a map by adding a dollar sign ($) prefix to its name. You also can use braces ({ }) to delimit the name of the variable from appended letters or digits.
Environment variables can be inherited from the environment
or can be defined explicitly with the
-D
option on the command line. For example, you can invoke the
automount
daemon with the
HOST
variable by entering the following command:
#
automount -D HOST= hostname
The following is an example of a direct map entry that uses the
environment variable
HOST
to define subnetworks:
/mydir -rw server:/export/$HOST
The
automount
daemon provides several ways to mount remote
directories and file systems:
When you write direct and indirect maps, you can specify that
different directories within a file system
hierarchy be mounted from different servers. For example, if you mount the
/usr/local
file system on your machine, you can mount the various subdirectories
within
/usr/local
from different servers.
The following example shows an entry in a direct map in which the directories
/usr/local/bin,
/usr/local/src,
and
/usr/local/tools
are mounted from the machines
host1,
host2,
and
host3,
respectively:
/usr/local\
/bin -ro host1:/usr/local/bin \
/src -ro host2:/usr/local/src \
/tools -ro host3:/usr/local/tools
This is a direct map because the
key,
/usr/local,
is an absolute pathname. If this were an entry in an indirect map, the
key
would be a simple pathname, such as
local.
The
key,
/usr/local,
comprises three
subdirectories, each of which is a mount point for a remote directory on a
different remote server. The example shows the entry split into four lines with
the continuation lines indented for readability.
The preceding example shows multiple, nonhierarchical mounts under
/usr/local.
The following example shows a true hierarchical entry:
/usr/local \
/ -ro host0:/usr/local \
/bin -ro host1:/usr/local/bin \
/src -ro host2:/usr/local/src \
/tools -ro host3:/usr/local/tools
The mount points used here for the hierarchy are
/,
/bin,
/src,
and
/tools.
Note that these mount points are relative to
/usr/local.
The mount point
/
mounts
/usr/local
from
host0.
When file systems are mounted hierarchically, the entire
hierarchy is treated as one object. Each file system is mounted on a
subdirectory within another file system, and when a subdirectory within the
hierarchy is referenced, the
automount
daemon mounts the entire
hierarchy. The entire hierarchy is also unmounted as one object.
When multiple directories within the same remote directory are mounted,
the
location
field can be specified as follows:
host:path:subdir
The
host
field is the remote host from which to mount the file
system. The
path
field is the pathname of the directory to
mount, and the
subdir
field, if specified, is the name of the
subdirectory to which the symbolic link is made. This prevents duplicate
mounts of the same remote file system when multiple subdirectories within it
are accessed. Suppose an indirect map called
/auto.myindirect
has the following entries:
mybin host1:/usr/staff/diane:bin mystuff host1:/usr/staff/diane:stuff
When a user accesses a file in
/auto.myindirect/mybin,
the
automount
daemon mounts
host1:/usr/staff/diane,
but creates a symbolic link called
/auto.myindirect/mybin
to the .L bin) subdirectory in
the temporarily mounted file system. If a user immediately tries to access a
file in
/auto.myindirect/mystuff,
the
automount
daemon needs only to create a symbolic link that points to the
mystuff
subdirectory because the
/usr/staff/diane
directory is already mounted. With the following map, the
automount
daemon must mount the file system twice:
mybin host1:/usr/staff/diane/bin mystuff host1:/usr/staff/diane/stuff
You can specify multiple locations for a single mount. If a file system is located on several servers and one of the servers is disabled, the file system can be mounted from one of the other servers. This makes sense only when mounting a read-only file system.
In the following example, the reference pages can be mounted from
host1,
machine2,
or
system3:
/usr/man\
-ro,soft host1:/usr/man \
machine2:/usr/man \
system3:/usr/man
The preceding example can also be expressed as a list of servers, separated by commas and followed by a colon and the pathname, for example:
/usr/man -ro,soft host1,machine2,system3:/usr/man
This syntax is valid only if the pathname is the same on each server.
When you access the reference pages, the
automount
daemon issues a
ping
command to each of the specified servers.
The server that first responds to the
ping
command is used for
the mount.