Chapter 5 About Autofs

This chapter describes the parts of the autofs service and gives more detailed information about the autofs maps.

• "Autofs Programs"

• "Autofs Maps"

• "How Autofs Works"

• "Autofs Reference"

Autofs Programs

Two programs support the autofs service. Both are run when a system is booted, but only automountd is persistent.

automount

This command installs autofs mount points and associates the information in the automaster files with each mount point. The syntax of the command is:

automount [ -t duration ] [ -v ]

where -t duration sets the time, in seconds, that a file system is to remain mounted, and -v selects the verbose mode. Running this command in the verbose mode allows for easier troubleshooting.

If not specifically set, the value for duration is set to 5 minutes. In most circumstances this is a good value; however, on systems that have many automounted file systems, you might need to increase the duration value. In particular, if a server has many users active, checking the automounted file systems every five minutes can be inefficient. Checking the autofs file systems every 1800 seconds (or 30 minutes) could be more optimal. By not unmounting the file systems every 5 minutes, it is possible that /etc/mnttab, which is checked by df, can become very large. The output from df can be filtered by using the -F option (see the df(1M) man page) or by using egrep to help fix this problem.

Another factor to consider is that adjusting the duration also changes how quickly changes to the automounter maps will be reflected. Changes will not be seen until the file system is unmounted. Refer to "Modifying the Maps" for instructions on how to modify automounter maps.

automountd

This daemon handles the mount and unmount requests from the autofs service. The syntax of the command is:

automountd [ -Tnv ] [ -D name=value ]

where -T selects to display each RPC call to standard output, -n disables browsing on all autofs nodes, -v selects to log all status messages to the console, and -D name=value substitutes value for the automount map variable indicated by name. The default value for the automount map is /etc/auto_master. Use the -T option for troubleshooting.

Autofs Maps

Autofs uses three types of maps:

• Master map

• Direct maps

• Indirect maps

Master 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 example below shows what an auto_master file could contain.

Example 5-1 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 ]

mount-point

mount-point is the full (absolute) path name of a directory. If the directory does not exist, autofs creates it if possible. If the directory exists and is not empty, mounting on it hides its contents. In this case, autofs issues a warning.

The notation /- as a mount point indicates that the map in question is a direct map, and no particular mount point is associated with the map as a whole.

map-name

map-name is the map autofs uses to find directions to locations, or mount information. If the name is preceded by a slash (/), autofs interprets the name as a local file. Otherwise, autofs searches for the mount information using the search specified in the name service switch configuration file (/etc/nsswitch.conf). Special maps are also used for /net and /xfn (see "Mount Point /net" and "Mount Point /xfn").

mount-options

mount-options is an optional, comma-separated list of options that apply to the mounting of the entries specified in map-name, unless the entries in map-name list other options. Options for each specific type of file system are listed in the mount man page for that file system (for example, see the mount_nfs(1M) man page for NFS specific mount options). For NFS specific mount points, the bg (background) and fg (foreground) options do not apply.

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.

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. Notice that 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 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

key

key is the path name of the mount point in a direct map.

mount-options

mount-options are the options you want to apply to this particular mount. They are required only if they differ from the map default. Options for each specific type of file system are listed in the mount man page for that file system (for example, see the mount_cachefs(1M) man page for CacheFS specific mount options).

location

location is the location of the file system, specified (one or more) as server:pathname for NFS file systems or :devicename for High Sierra file systems (HSFS).

---

Note -

The pathname should not include an automounted mount point; it should be the actual absolute path to the file system. For instance, the location of a home directory should be listed as server:/export/home/username, not as server:/home/username.

---

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, in their simplest form, 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 

There is 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 would be overwritten 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 5-1, 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 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

key

key is a simple name (no slashes) in an indirect map.

mount-options

The mount-options are the options you want to apply to this particular mount. They are required only if they differ from the map default. Options for each specific type of file system are listed in the mount man page for that file system (for example, see the mount_nfs(1M) man page for NFS specific mount options).

location

location is the location of the file system, specified (one or more) as server:pathname.

---

Note -

The pathname should not include an automounted mount point; it should be the actual absolute path to the file system. For instance, the location of a directory should be listed as server:/usr/local not as server:/net/server/usr/local.

---

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 5-1 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, then 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).

There is 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 overwritten 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.

How Autofs Works

Autofs is a client-side service that automatically mounts the appropriate file system. When a client attempts to access a file system that is not presently mounted, the autofs file system intercepts the request and calls automountd, to mount the requested directory. The automountd daemon locates the directory, mounts it within autofs, and replies. On receiving the reply, autofs allows the waiting request to proceed. Subsequent references to the mount are redirected by the autofs--no further participation is required by automountd, until the file system is automatically unmounted by autofs after a period of inactivity.

The components that work together to accomplish automatic mounting are:

• The automount command

• The autofs file system

• The automountd daemon

The automount command, called at system startup time, reads the master map file auto_master to create the initial set of autofs mounts. These autofs mounts are not automatically mounted at startup time. They are points under which file systems are mounted in the future. These points are also known as trigger nodes.

After the autofs mounts are set up, they can trigger file systems to be mounted under them. For example, when autofs receives a request to access a file system that is not currently mounted, autofs calls automountd, which actually mounts the requested file system.

Starting with the Solaris 2.5 release, the automountd daemon is completely independent from the automount command. Because of this separation, it is possible to add, delete, or change map information without first having to stop and start the automountd daemon process.

After initially mounting autofs mounts, the automount command is used to update autofs mounts as necessary, by comparing the list of mounts in the auto_master map with the list of mounted file systems in the mount table file /etc/mnttab (formerly /etc/mtab) and making the appropriate changes. This allows system administrators to change mount information within auto_master and have those changes used by the autofs processes without having to stop and restart the autofs daemon. After the file system is mounted, further access does not require any action from automountd until the file system is automatically unmounted.

Unlike mount, automount does not read the /etc/vfstab file (which is specific to each computer) for a list of file systems to mount. The automount command is controlled within a domain and on computers through the name space or local files.

This is a simplified overview of how autofs works:

The automount daemon automountd starts at boot time from the /etc/init.d/autofs script (See Figure 5-1). This script also runs the automount command, which reads the master map (see "How Autofs Starts the Navigation Process (Master Map)") and installs autofs mount points.

Figure 5-1 /etc/init.d/autofs Script Starts automount

Autofs is a kernel file system that supports automatic mounting and unmounting.

When a request is made to access a file system at an autofs mount point:

1. Autofs intercepts the request.

2. Autofs sends a message to the automountd for the requested file system to be mounted.

3. automountd locates the file system information in a map, creates the trigger nodes, and performs the mount.

4. Autofs allows the intercepted request to proceed.

5. Autofs unmounts the file system after a period of inactivity.

Mounts managed through the autofs service should not be manually mounted or unmounted. Even if the operation is successful, the autofs service does not check that the object has been unmounted, resulting in possible inconsistency. A reboot clears all of the autofs mount points.

How Autofs Navigates Through the Network (Maps)

Autofs searches a series of maps to navigate its way through the network. Maps are files that contain information such as the password entries of all users on a network or the names of all host computers on a network, that is, network-wide equivalents of UNIX administration files. Maps are available locally or through a network name service like NIS or NIS+. You create maps to meet the needs of your environment using the Solstice System Management Tools. See "Modifying How Autofs Navigates the Network (Modifying Maps)".

How Autofs Starts the Navigation Process (Master Map)

The automount command reads the master map at system startup. Each entry in the master map is a direct or indirect map name, its path, and its mount options, as shown in Figure 5-2. The specific order of the entries is not important. automount compares entries in the master map with entries in the mount table to generate a current list.

Figure 5-2 Navigation Through the Master Map

Autofs Mount Process

What the autofs service does when a mount request is triggered depends on how the automounter maps are configured. The mount process is generally the same for all mounts, but the final result changes with the mount point specified and the complexity of the maps. Starting with the Solaris 2.6 release, the mount process has also been changed to include the creation of the trigger nodes.

A Simple Autofs Mount

To help explain the autofs mount process, assume that the following files are installed.

$ cat /etc/auto_master
# Master map for automounter
#
+auto_master
/net        -hosts        -nosuid,nobrowse
/home       auto_home     -nobrowse
/xfn        -xfn
/share      auto_share
$ cat /etc/auto_share
# share directory map for automounter
#
ws          gumbo:/export/share/ws

When the /share directory is accessed, the autofs service creates a trigger node for /share/ws, which can be seen in /etc/mnttab as an entry that resembles the following entry:

-hosts  /share/ws     autofs  nosuid,nobrowse,ignore,nest,dev=###

When the /share/ws directory is accessed, the autofs service completes the process with these steps:

1. Pings the server's mount service to see if it's alive

2. Mounts the requested file system under /share. Now /etc/mnttab file contains the following entries:

   -hosts /share/ws autofs nosuid,nobrowse,ignore,nest,dev=### gumbo:/export/share/ws /share/ws nfs nosuid,dev=#### #####

Hierarchical Mounting

When multiple layers are defined in the automounter files, the mount process becomes more complex. If the /etc/auto_shared file from the previous example is expanded to contain:

# share directory map for automounter
#
ws       /       gumbo:/export/share/ws
         /usr    gumbo:/export/share/ws/usr

The mount process is basically the same as the previous example when the /share/ws mount point is accessed. In addition, a trigger node to the next level (/usr) is created in the /share/ws file system so that the next level can be mounted if it is accessed. In this example, /export/share/ws/usr must exist on the NFS server for the trigger node to be created.

Do not use the -soft option when specifying hierarchical layers. Refer to "Autofs Unmounting" for an explanation of this limitation.

Autofs Unmounting

The unmounting that occurs after a certain amount of idle time is from the bottom up (reverse order of mounting). If one of the directories at a higher level in the hierarchy is busy, only file systems below that directory are unmounted. During the unmounting process, any trigger nodes are removed and then the file system is unmounted. If the file system is busy, the unmount fails and the trigger nodes are reinstalled.

Do not use the -soft option when specifying hierarchical layers. If the -soft option is used, requests to reinstall the trigger nodes can timeout. The failure to reinstall the trigger notes leaves no access to the next level of mounts. The only way to clear this problem is to have the automounter unmount all of the components in the hierarchy, either by waiting for the file systems to be automatically unmounted or by rebooting the system.

How Autofs Selects the Nearest Read-Only Files for Clients (Multiple Locations)

In the example of a direct map, which was:

/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 

The mount points /usr/man and /usr/spool/news list more than one location (three for the first, two for the second). This means any of the replicated locations can provide the same service to any user. This procedure makes sense only when you mount a file system that is read-only, as you must have some control over the locations of files you write or modify. You don't want to modify files on one server on one occasion and, minutes later, modify the "same" file on another server. The benefit is that the best available server is used automatically without any effort required by the user.

If the file systems are configured as replicas (see "What Is a Replicated File System?"), then the clients have the advantage of using failover. Not only is the best server automatically determined, but if that server becomes unavailable, the client automatically uses the next-best server. Failover is a new feature implemented in the Solaris 2.6 release.

An example of a good file system to configure as a replica is man pages. In a large network, more than one server can export the current set of manual pages. Which server you mount them from does not matter, as long as the server is running and exporting its file systems. In the previous example, multiple mount locations are expressed as a list of mount locations in the map entry.

/usr/man -ro oak:/usr/man rose:/usr/man willow:/usr/man 

Here you can mount the man pages from the servers oak, rose, or willow. Which server is best depends on a number of factors including: the number of servers supporting a particular NFS protocol level, the proximity of the server, and weighting.

During the sorting process, a count of the number of servers supporting the NFS version 2 and NFS version 3 protocols is made. Whichever protocol is supported on the most servers becomes the protocol supported by default. This provides the client with the maximum number of servers to depend on.

Once the largest subset of servers with the same protocol version is found, that server list is sorted by proximity. Servers on the local subnet are given preference over servers on a remote subnet. The closest server is given preference, which reduces latency and network traffic. Figure 5-3 illustrates server proximity.

Figure 5-3 Server Proximity

If several servers supporting the same protocol are on the local subnet, the time to connect to each server is determined and the fastest is used. The sorting can also be influenced by using weighting (see "Autofs and Weighting").

If version 3 servers are more abundant, the sorting process becomes more complex. Normally, servers on the local subnet are given preference over servers on a remote subnet. A version 2 server can complicate matters, as it might be closer than the nearest version 3 server. If there is a version 2 server on the local subnet and the closest version 3 server is on a remote subnet, the version 2 server is given preference. This preference is only checked if there are more version 3 servers than version 2 servers. If there are more version 2 servers, then only a version 2 server is selected.

With failover, the sorting is checked once at mount time to select one server from which to mount, and again anytime the mounted server becomes unavailable. Multiple locations are useful in an environment where individual servers might not export their file systems temporarily.

This feature is particularly useful in a large network with many subnets. Autofs chooses the nearest server and therefore confines NFS network traffic to a local network segment. In servers with multiple network interfaces, list the host name associated with each network interface as if it were a separate server. Autofs selects the nearest interface to the client.

Autofs and Weighting

You can influence the selection of servers at the same proximity level by adding a weighting value to the autofs map. For example:

/usr/man -ro oak,rose(1),willow(2):/usr/man

The numbers in parentheses indicate a weighting. Servers without a weighting have a value of zero (most likely to be selected). The higher the weighting value, the lower the chance the server will be selected.

All other server selection factors are more important than weighting. Weighting is only considered when selecting between servers with the same network proximity.

Variables in a Map Entry

You can create a client-specific variable by prefixing a dollar sign ($) to its name. This helps you to accommodate different architecture types accessing the same file system location. You can also use curly braces to delimit the name of the variable from appended letters or digits. Table 5-1 shows the predefined map variables.

You can use variables anywhere in an entry line except as a key. For instance, if you have a file server exporting binaries for SPARC and x86 architectures from /usr/local/bin/sparc and /usr/local/bin/x86 respectively, the clients can mount through a map entry like the following:

/usr/local/bin	   -ro	server:/usr/local/bin/$CPU

Now the same entry for all clients applies to all architectures.

Most applications written for any of the sun4 architectures can run on all sun4 platforms, so the -ARCH variable is hardcoded to sun4 instead of sun4m or sun4c.

Maps That Refer to Other Maps

A map entry +mapname used in a file map causes automount to read the specified map as if it were included in the current file. If mapname is not preceded by a slash, then autofs treats the map name as a string of characters and uses the name service switch policy to find it. If the path name is an absolute path name, then automount looks for a local map of that name. If the map name starts with a dash (-), automount consults the appropriate built-in map, such as xfn or hosts.

This name service switch file contains an entry for autofs labeled as automount, which contains the order in which the name services are searched. The following file is an example of a name service switch file:

#
# /etc/nsswitch.nis:
#
# An example file that could be copied over to /etc/nsswitch.conf;
# it uses NIS (YP) in conjunction with files.
#
# "hosts:" and "services:" in this file are used only if the /etc/netconfig
# file contains "switch.so" as a nametoaddr library for "inet" transports.
# the following two lines obviate the "+" entry in /etc/passwd and /etc/group.
passwd:         files nis
group:          files nis

# consult /etc "files" only if nis is down.
hosts:          nis [NOTFOUND=return] files
networks:       nis [NOTFOUND=return] files
protocols:      nis [NOTFOUND=return] files
rpc:            nis [NOTFOUND=return] files
ethers:         nis [NOTFOUND=return] files
netmasks:       nis [NOTFOUND=return] files
bootparams:     nis [NOTFOUND=return] files
publickey:      nis [NOTFOUND=return] files
netgroup:       nis
automount:      files nis
aliases:        files nis
# for efficient getservbyname() avoid nis
services:       files nis 

In this example, the local maps are searched before the NIS maps, so you can have a few entries in your local /etc/auto_home map for the most commonly accessed home directories, and use the switch to fall back to the NIS map for other entries.

bill               cs.csc.edu:/export/home/bill
bonny              cs.csc.edu:/export/home/bonny

After consulting the included map, if no match is found, automount continues scanning the current map. This means you can add more entries after a + entry.

bill               cs.csc.edu:/export/home/bill
bonny              cs.csc.edu:/export/home/bonny
+auto_home 

The map included can be a local file (remember, only local files can contain + entries) or a built-in map:

+auto_home_finance      # NIS+ map
+auto_home_sales        # NIS+ map
+auto_home_engineering  # NIS+ map
+/etc/auto_mystuff      # local map
+auto_home              # NIS+ map
+-hosts                 # built-in hosts map 

You cannot use + entries in NIS+ or NIS maps.

Executable Autofs Maps

You can create an autofs map that will execute some commands to generate the autofs mount points. You could benefit from using an executable autofs map if you need to be able to create the autofs structure from a database or a flat file. The disadvantage to using an executable map is that the map will need to be installed on each host. An executable map cannot be included in either the NIS or the NIS+ name service.

The executable map must have an entry in the auto_master file.

/execute    auto_execute

Here is an example of an executable map:

#!/bin/ksh
#
# executable map for autofs
#

case $1 in
	         src)  echo '-nosuid,hard bee:/export1' ;;
esac

For this example to work, the file must be installed as /etc/auto_execute and must have the executable bit set (set permissions to 744). Under these circumstances running the following command:

% ls /execute/src

causes the /export1 file system from bee to be mounted.

Modifying How Autofs Navigates the Network (Modifying Maps)

You can modify, delete, or add entries to maps to meet the needs of your environment. As applications and other file systems that users require change their location, the maps must reflect those changes. You can modify autofs maps at any time. Whether your modifications take effect the next time automountd mounts a file system depends on which map you modify and what kind of modification you make.

Default Autofs Behavior With Name Services

Booting invokes autofs using the /etc/init.d/autofs script and checks for the master auto_master map (subject to the rules discussed subsequently).

Autofs uses the name service specified in the automount entry of the /etc/nsswitch.conf file. If NIS+ is specified, as opposed to local files or NIS, all map names are used as is. If NIS is selected and autofs cannot find a map that it needs, but finds a map name that contains one or more underscores, the underscores are changed to dots, which allows the old NIS file names to work. Then autofs looks up the map again, as shown in Figure 5-4.

Figure 5-4 How Autofs Uses the Name Service

The screen activity for this session would look like the following example.

$ grep /home /etc/auto_master
/home           auto_home

$ ypmatch brent auto_home
Can't match key brent in map auto_home.  Reason: no such map in
server's domain.

$ ypmatch brent auto.home
diskus:/export/home/diskus1/&

If "files" is selected as the name service, all maps are assumed to be local files in the /etc directory. Autofs interprets a map name that begins with a slash (/) as local regardless of which name service it uses.

Autofs Reference

The rest of this chapter describes more advanced autofs features and topics.

Metacharacters

Autofs recognizes some characters as having a special meaning. Some are used for substitutions, some to protect other characters from the autofs map parser.

Ampersand (&)

If you have a map with many subdirectories specified, as in the following, consider using string substitutions.

john        willow:/home/john
mary        willow:/home/mary
joe         willow:/home/joe
able        pine:/export/able
baker       peach:/export/baker

You can use the ampersand character (&) to substitute the key wherever it appears. If you use the ampersand, the previous map changes to:

john        willow:/home/&
mary        willow:/home/&
joe         willow:/home/&
able        pine:/export/&
baker       peach:/export/&

You could also use key substitutions in a direct map, in situations like this:

/usr/man						willow,cedar,poplar:/usr/man

which you can also write as:

/usr/man						willow,cedar,poplar:&

Notice that the ampersand substitution uses the whole key string, so if the key in a direct map starts with a / (as it should), the slash is carried over, and you could not do, for example, the following:

/progs				&1,&2,&3:/export/src/progs 

because autofs would interpret it as:

/progs 				/progs1,/progs2,/progs3:/export/src/progs

Asterisk (*)

You can use the universal substitute character, the asterisk (*), to match any key. You could mount the /export file system from all hosts through this map entry.

*						&:/export

Each ampersand is substituted by the value of any given key. Autofs interprets the asterisk as an end-of-file character.

Special Characters

If you have a map entry that contains special characters, you might have to mount directories whose names confuse the autofs map parser. The autofs parser is sensitive to names containing colons, commas, spaces, and so on. These names should be enclosed in double quotations, as in the following:

/vms    -ro    vmsserver: -  -  - "rc0:dk1 - "
/mac    -ro    gator:/ - "Mr Disk - "