About Autofs

File systems shared through the NFS service can be mounted using automatic mounting. Autofs, a client-side service, is a file system structure that provides automatic mounting. The autofs file system is initialized by automount, which is run automatically when a system is booted. The automount daemon, automountd, runs continuously, mounting and unmounting remote directories on an as-needed basis.

Whenever a user on a client computer running automountd tries to access a remote file or directory, the daemon mounts the file system to which that file or directory belongs. This remote file system remains mounted for as long as it is needed. If the remote file system is not accessed for a certain period of time, it is automatically unmounted.

Mounting need not be done at boot time, and the user no longer has to know the superuser password to mount a directory; users need not use the mount and umount commands. The autofs service mounts and unmounts file systems as required without any intervention on the part of the user.

Mounting some file hierarchies with automountd does not exclude the possibility of mounting others with mount. A diskless computer must mount / (root), /usr, and /usr/kvm through the mount command and the /etc/vfstab file.

"Autofs Administration Task Overview" and "How Autofs Works" give more specific information about the autofs service.

Autofs Features

Autofs works with file systems specified in the local name space. This information can be maintained in NIS, NIS+, or local files.

A fully multithreaded version of automountd was included in the Solaris 2.6 release. This enhancement makes autofs more reliable and allows for concurrent servicing of multiple mounts, which prevents the service from hanging if a server is unavailable.

The new automountd also provides better on-demand mounting. Previous releases would mount an entire set of file systems if they were hierarchically related. Now only the top file system is mounted. Other file systems related to this mount point are mounted when needed.

The autofs service supports browsability of indirect maps. This support allows a user to see what directories could be mounted, without having to actually mount each one of the file systems. A -nobrowse option has been added to the autofs maps, so that large file systems, such as /net and /home, are not automatically browsable. Also, you can turn off autofs browsability on each client by using the -n option with automount.