Autofs Maps

Autofs uses three types of maps:

• Master map

• Direct maps

• Indirect maps

Master Autofs Map

The auto_master map associates a directory with a map. It is a master list specifying all the maps that autofs should check. The following example shows what an auto_master file could contain.

Example 31-1 Sample /etc/auto_master File

# Master map for automounter 
# 
+auto_master 
/net            -hosts           -nosuid,nobrowse 
/home           auto_home        -nobrowse 
/xfn            -xfn
/-              auto_direct     -ro  

This example shows the generic auto_master file with one addition for the auto_direct map. Each line in the master map /etc/auto_master has the following syntax:

mount-point map-name [ mount-options ]

A line beginning with # is a comment. Everything that follows until the end of the line is ignored.

To split long lines into shorter ones, put a backslash (\) at the end of the line. The maximum number of characters of an entry is 1024.

If the same mount point is used in two entries, the first entry is used by the automount command. The second entry is ignored.

Mount Point /home

The mount point /home is the directory under which the entries listed in /etc/auto_home (an indirect map) are to be mounted.

Autofs runs on all computers and supports /net and /home (automounted home directories) by default. These defaults can be overridden by entries in the NIS auto.master map or NIS+ auto_master table, or by local editing of the /etc/auto_master file.

Mount Point /net

Autofs mounts under the directory /net all the entries in the special map -hosts. This is a built-in map that uses only the hosts database. For example, if the computer gumbo is in the hosts database and it exports any of its file systems, the command:

%cd /net/gumbo

changes the current directory to the root directory of the computer gumbo. Autofs can mount only the exported file systems of host gumbo, that is, those on a server available to network users as opposed to those on a local disk. Therefore, all the files and directories on gumbo might not be available through /net/gumbo.

With the /net method of access, the server name is in the path and is location dependent. If you want to move an exported file system from one server to another, the path might no longer work. Instead, you should set up an entry in a map specifically for the file system you want rather than use /net.

Autofs checks the server's export list only at mount time. After a server's file systems are mounted, autofs does not check with the server again until the server's file systems are automatically unmounted. Therefore, newly exported file systems are not "seen" until the file systems on the client are unmounted and then remounted.

Mount Point /xfn

This mount point provides the autofs directory structure for the resources that are shared through the FNS name space (see the Solaris Naming Setup and Configuration Guide for more information about FNS).

Direct Autofs Maps

A direct map is an automount point. With a direct map, there is a direct association between a mount point on the client and a directory on the server. Direct maps have a full path name and indicate the relationship explicitly. This is a typical /etc/auto_direct map:

/usr/local          -ro \
   /bin                   ivy:/export/local/sun4 \
   /share                 ivy:/export/local/share \
   /src                   ivy:/export/local/src
   /usr/man         -ro   oak:/usr/man \
                          rose:/usr/man \
                          willow:/usr/man 
   /usr/games       -ro   peach:/usr/games 
   /usr/spool/news  -ro   pine:/usr/spool/news \
                          willow:/var/spool/news 

Lines in direct maps have the following syntax:

key [ mount-options ] location

As in the master map, a line beginning with # is a comment. All the text that follows until the end of the line is ignored. Put a backslash at the end of the line to split long lines into shorter ones.

Of all the maps, the entries in a direct map most closely resemble the corresponding entries in /etc/vfstab (vfstab contains a list of all file systems to be mounted). An entry that appears in /etc/vfstab as:

dancer:/usr/local - /usr/local/tmp nfs - yes ro 

appears in a direct map as:

/usr/local/tmp     -ro     dancer:/usr/local 

No concatenation of options occurs between the automounter maps. Any options added to an automounter map override all options listed in maps that are searched earlier. For instance, options included in the auto_master map would be overridden by corresponding entries in any other map.

See "How Autofs Selects the Nearest Read-Only Files for Clients (Multiple Locations)" for other important features associated with this type of map.

Mount Point /-

In Example 31-1, the mount point /- tells autofs not to associate the entries in auto_direct with any specific mount point. Indirect maps use mount points defined in the auto_master file. Direct maps use mount points specified in the named map. (Remember, in a direct map the key, or mount point, is a full path name.)

An NIS or NIS+ auto_master file can have only one direct map entry because the mount point must be a unique value in the name space. An auto_master file that is a local file can have any number of direct map entries, as long as entries are not duplicated.

Indirect Autofs Maps

An indirect map uses a substitution value of a key to establish the association between a mount point on the client and a directory on the server. Indirect maps are useful for accessing specific file systems, like home directories. The auto_home map is an example of an indirect map.

Lines in indirect maps have the following general syntax:

key [ mount-options ] location

As in the master map, a line beginning with # is a comment. All the text that follows until the end of the line is ignored. Put a backslash (\) at the end of the line to split long lines into shorter ones. Example 31-1 shows an auto_master map that contains the entry:

/home      auto_home        -nobrowse    

auto_home is the name of the indirect map that contains the entries to be mounted under /home. A typical auto_home map might contain:

david                  willow:/export/home/david
rob                    cypress:/export/home/rob
gordon                 poplar:/export/home/gordon
rajan                  pine:/export/home/rajan
tammy                  apple:/export/home/tammy
jim                    ivy:/export/home/jim
linda    -rw,nosuid    peach:/export/home/linda

As an example, assume that the previous map is on host oak. If user linda has an entry in the password database specifying her home directory as /home/linda, whenever she logs in to computer oak, autofs mounts the directory /export/home/linda residing on the computer peach. Her home directory is mounted read-write, nosuid.

Assume the following conditions occur: User linda's home directory is listed in the password database as /home/linda. Anybody, including Linda, has access to this path from any computer set up with the master map referring to the map in the previous example.

Under these conditions, user linda can run login or rlogin on any of these computers and have her home directory mounted in place for her.

Furthermore, now Linda can also type the following command:

% cd ~david

autofs mounts David's home directory for her (if all permissions allow).

No concatenation of options between the automounter maps. Any options added to an automounter map override all options listed in maps that are searched earlier. For instance, options included in the auto_master map are overidden by corresponding entries in any other map.

On a network without a name service, you have to change all the relevant files (such as /etc/passwd) on all systems on the network to accomplish this. With NIS, make the changes on the NIS master server and propagate the relevant databases to the slave servers. On a network running NIS+, propagating the relevant databases to the slave servers is done automatically after the changes are made.