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. You can then 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 that is 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 |
Note - You cannot use + entries in NIS+ or NIS maps.
Executable Autofs Maps
You can create an autofs map that executes 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 needs 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 causes the /export1 file system from bee to be mounted:
% ls /execute/src |
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 are effective 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 by using the /etc/init.d/autofs script and checks for the master auto_master map (subject to the rules that are discussed subsequently).
Autofs uses the name service that is 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. This change allows the old NIS file names to work. Then autofs checks the map again, as shown in Figure 16-4.
Figure 16-4 How Autofs Uses the Name Service
The screen activity for this session would resemble 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 remaining sections of this chapter describe more advanced autofs features and topics.
Metacharacters
Autofs recognizes some characters as having a special meaning. Some characters are used for substitutions, and some are used 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 the following:
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 such as the following:
/usr/man willow,cedar,poplar:/usr/man |
You can also simplify the entry further as follows:
/usr/man willow,cedar,poplar:& |
Notice that the ampersand substitution uses the whole key string. Therefore, 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 |
The reason is that autofs would interpret the example as the following:
/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 that have names that confuse the autofs map parser. The autofs parser is sensitive to names that contain 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 - " |