NFS Services Administrator's Guide

Configuring and Administering AutoFS
How AutoFS Works
Chapter 3102
How AutoFS Works
This section describes how AutoFS works.
AutoFS mounts directories automatically when users or processes
request access to them, and it unmounts directories automatically if they
remain idle for a period of time (10 minutes, by default).
When deciding if AutoFS is right for your environment, see “Deciding
Between Standard-Mounted Directories and Automounted Directories”
on page 75.
AutoFS consists of the following components:
•The automount command which reads AutoFS maps into memory
• The AutoFS filesystem
•The automountd daemon, which automounts filesystems when they
are accessed by users or applications
The automount command reads the AutoFS master map to create the
initial set of AutoFS mount points in the kernel mount table,
/etc/mnttab. The automounted filesystems are not automatically
mounted at startup. They are points under which filesystems are
mounted later, when users or applications request access to them.
When AutoFS receives a request to mount a filesystem, it calls the
automountd daemon, which mounts the requested filesystem. Once the
filesystem is mounted, further access does not require any action from
the automountd daemon.
The automountd daemon is independent from the automount command.
As a result, you can add, delete, or change map information without
stopping and restarting the automountd daemon.
Once AutoFS starts and the mount points are set up, you can modify the
set of mount points by modifying maps and running the automount
command, to read them and modify the mount table accordingly. You
need not stop and restart AutoFS.
If an automounted filesystem remains idle for 10 minutes (the default),
AutoFS unmounts it.
For more information on AutoFS, see automount (1M) and
automountd (1M).