# $Source: /source/hpux_source/networking/rcs/nfs90_800/doc/IMS/automount/RCS/overview,v $
# $Revision: 1.2.109.1 $	$Author: gomathi $
# $State: Exp $   	$Locker:  $
# $Date: 92/04/13 16:45:58 $

\" -*-Nroff-*-   \" set Nroff mode for emacs
.H 1 "General Overview"
.tl '   '\f3\l'6i\f1''   '

.H 2 "What is Automount?"

     Automount is an automatic filesytem mounting service for NFS
filesystems.  Automount detects access to remote filesystems and mounts
them on demand.  The detection and following mounting is transparent to users
and user programs.  After some period of inactivity in automounted
filesystems automount automatically unmounts them.  Map files are used
to configure and direct automount's activities.  The map files can be
set up with multiple server names for a given filesystem that is replicated
across the network.  These maps can also specify mount hierarchies.  The
automount maps can be set up as local files on the client system or
administered through a NIS (Network Information Service) domain.

.H 2 "Why use Automount?"

    Automount provides even more transparent access to files accross
the network than NFS alone does.  With automount properly configured
a user can access any file on the network with a unix pathname and leave
automount the task of finding it and mounting the filesytem containing it.
Automount is extremely helpful in a large network with many NFS servers.
If a particular client node needs access to a large portion of the exported
filesystems on the network it would normally have to mount all the needed
filesystems.  However with automount the filesystems are mounted on
demand and thus only the filesystems that actually get used are mounted
at any given time.

.H 2 "How does it really work?"

    Automount is a user level server for the Network File System, NFS.
Automount does not require any explicit support from the kernel beyond
what is required for NFS.  The automount server is a daemon (/etc/automount)
that runs on NFS clients, and emulates NFS daemons (/etc/nfsd) that run on
NFS servers.  Automount intercepts NFS requests that would normally
go to an NFS server daemon.  Automount then consults its internal
tables to see if the requested filesystem is already mounted.  If it is not
already mounted, automount mounts the remote filesystem (possibly
considering a list of choices for the particular server to use).  The
details of this is the topic of the rest of this document.
