Special Maps

There are two special maps available: -hosts and null. The -hosts map is used with the /net directory and assumes that the map key is the host name of an NFS server. The automountd daemon dynamically constructs a map entry from the server's list of exported file systems. For example, a reference to /net/sales/usr would initiate an automatic mount of all exported file systems from sales that are mountable by the client. References to a directory under /net/sales would refer to the corresponding directory relative to the sales root.

The -null map, when indicated on the command line, cancels a previous map for the directory indicated. This is used in the /etc/auto_master map for canceling entries that would otherwise be inherited from the +auto_master include entry. The -null entries must be inserted before the included map entry.