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21.3.3.3. Adapting Autofs v4 Maps To Autofs v5

v4 Multi-map entries

Autofs version 4 introduced the notion of a multi-map entry in the master map. A multi-map entry is of the form: 

<mount-point> <maptype1> <mapname1> <options1> -- <maptype2> <mapname2> <options2> -- ...
Any number of maps can be combined into a single map in this manner. This feature is no longer present in v5. This is because Version 5 supports included maps which can be used to attain the same results. Consider the following multi-map example: 
/home file /etc/auto.home -- nis auto.home
This can be replaced by the following configuration for v5:
/etc/nsswitch.conf must list: 
automount: files nis
/etc/auto.master should contain: 
/home  auto.home
/etc/auto.home should contain: 
<entries for the home directory>
+auto.home
In this way, the entries from /etc/auto.home and the nis auto.home map are combined.
Multiple master maps

In autofs version 4, it is possible to merge the contents of master maps from each source, such as files, nis, hesiod, and LDAP. The version 4 automounter looks for a master map for each of the sources listed in /etc/nsswitch.conf. The map is read if it exists and its contents are merged into one large auto.master map.

In version 5, this is no longer the behaviour. Only the first master map found from the list of sources in nsswitch.conf is consulted. If it is desirable to merge the contents of multiple master maps, included maps can be used. Consider the following example: 
/etc/nsswitch.conf:
automount: files nis
/etc/auto.master:
/home  /etc/auto.home
+auto.master
The above configuration will merge the contents of the file-based auto.master and the NIS-based auto.master. However, because included map entries are only allowed in file maps, there is no way to include both an NIS auto.master and an LDAP auto.master.
This limitation can be overcome by creating a master maps that have a different name in the source. In the example above if we had an LDAP master map named auto.master.ldap we could also add "+auto.master.ldap" to the file based master map and provided that "ldap" is listed as a source in our nsswitch configuration it would also be included.