In this chapter, you will

• Gain an understanding of the role of the automounter

• Use automounter maps

• Create direct, indirect, and master maps

The automounter is a program that automatically mounts NFS file systems when they are accessed and then unmounts them when they are no longer needed. It requires you to use special files, known as automounter maps, which contain information about the servers, the pathname to the NFS file system on the server, the local pathname, and the mount options. By using the automounter, you don't have to update the entries in /etc/vfstab on every client by hand every time you make a change to the NFS servers.

Normally, only root can mount file systems, so when users need to mount an NFS file system, they need to find the system administrator. The main problem is that once users are finished with a file system, they rarely tell the system administrator. If the NFS server containing that file system ever crashed, you would be left with one or more hanging processes. This can easily increase your workload if you are responsible for maintaining an NFS server. The automounter can solve both of these problems, because it automatically mounts an NFS file system when a user references a file in that file system and it will automatically unmount the NFS file system if it is not referenced for more than five minutes.

The automounter is a RPC daemon that services requests from clients to mount and unmount remote volumes using NFS. During installation, a set of server-side maps are created that list the file systems to be automatically mounted. Typically, these file systems include shared user home directories (under /home), and network-wide mail directories (/var/mail).