NFS Services Administrator's Guide (B.11.31.03) August 2008

This enables AutoFS to ignore the map entry that does not apply to your host.
Notes on the -null Map
The -null map is used to ignore mapping entries that do not apply to your host, but
which would otherwise be inherited from the NIS or LDAP maps.
The -null option causes AutoFS to ignore AutoFS map entries that affect the specified
directory. For example, an NIS (or LDAP) auto_master map is configured such that
AutoFS mounts the auto_home map on /home, as follows:
/home auto_home
You can include the following line in the /etc/auto_master file, before the
+auto_master entry, so that the NIS auto_home map is not used for the system:
/home -null
+auto_master
NOTE: The -null entry must precede the included map entry to be effective.
Using Executable Maps
An executable map is a map whose entries are generated dynamically by a program
or a script. AutoFS determines whether a map is executable, by checking whether the
execute bit is set in its permissions string. If a map is not executable, ensure that its
execute bit is not set. An executable map is an indirect map.
When the AutoFS daemon locates a map whose execute bit is set, then instead of
opening the file and searching for an entry, the daemon executes the file as a program
and passes the key to be located within the map as an argument. Executable AutoFS
maps return a map entry on the standard output. If they cannot supply a map entry
for the key, they do not return anything. You can list executable AutoFS maps in the
master map or include them in the local AutoFS map files. However, executable maps
cannot be used with NIS and LDAP.
For example, an executable map implemented as a shell script, emulates the AutoFS
built-in -hosts map for /net. It obtains a list of exported file systems from an NFS
server (its name is the key argument). It then formats the path names into a
multiple-mount map entry and sorts the list to order the mounts correctly into a
top-down hierarchy, as follows:
!/bin/sh
Server=$1
showmount -e $1 | awk ‘NR > 1 {print $1 “\t'$Server’:” $1 ” \\ “}’ | sort
96 Configuring and Administering AutoFS