AutoFS for Mounting and Unmounting NFS File Systems

HP-UX 11.0 Extension Pack provides a daemon that mounts and unmounts NFS file systems automatically. This feature is known as AutoFS.

AutoFS coexists with automount and performs the same functions as automount, but has a new, more reliable design. Additionally, AutoFS supports the NFS PV3 protocol, whereas the automounter does not. The automount command has been replaced with a shell script that will either invoke the old Automount daemon or the new AutoFS automount command, depending on the variable AUTOFS in /etc/rc.config.d/nfsconf.

AUTOFS=1 causes /sbin/init.d/nfs.client to start the AutoFS daemon (automountd) and run the Autofs automount command.
AUTOFS=0 starts the old automount daemon. This is the default on newly installed or updated systems.

The old automount executable are located at:

/usr/lib/netsvc/fs/automount/automount

The new Autofs executables are located at:

/usr/lib/netsvc/fs/autofs/automountd /usr/lib/netsvc/fs/autofs/automount

When AutoFS is executed, a process used by its kernel code for kernel thread support is also started. The autofs_proc process cannot be killed, except by a shutdown of the system.

Impact

From an operational standpoint, AutoFS functions comparably to the old automounter and returns the same values.

From the system administrator's standpoint, however, AutoFS is started, stopped and updated differently than its predecessor. The nfs.client start-script automatically starts and stops the correct daemons, depending on the value of AUTOFS in /etc/rc.config.d/nfsconf.




	NOTE: If you do not use this script, you must bear in mind which implementation of automatic NFS file mounting you are using. Starting both AutoFS and automounter can lead to problems accessing the remote file system. You must reboot if you plan to switch between AutoFS and the old automounter.

Other Operational Differences

Any user-written scripts that expect the automount command to remain running as a daemon will have to be updated either to not expect this behavior, or to check explicitly that automountd is running. AutoFS can no longer be shut down by killing the automount process; instead, you must shut it down by executing the following command:

/sbin/init.d/nfs.client stop

This will unmount all mounted AutoFS filesystems and then kill the automountd process.

If you try to stop AutoFS without using /sbin/init.d/nfs.client script you must do the following:

/usr/sbin/umountall -F autofs kill <automountd_pid>

The -n, -M, and -tw options of the automount command are not supported at all in AutoFS. The -m and -tm options are not supported, but their behavior can be configured in different ways:

by modifying the nsswitch.conf file to get the -m behavior, and
by modifying the automount map entries to specify the timeout for the -tm option. The -tl option is accessed using -t.

Another difference between automounter and AutoFS is that AutoFS no longer uses symbolic links to access the mount points. Applications that depend on this explicit behavior will no longer work as expected.

Configuration

To enable AutoFS, you must add or the set the AUTOFS variable to 1 in /etc/rc.config.d/nfsconf. Here is an example of this change:

#autofs configuration. See autofs(1m) 
#
#For the 11.0 Release line both AUTOFS and the old Automount 
#are delivered. In order to invoke the AUTOFS instead of 
#you must set the AUTOFS flag to 1. 
#
#/usr/sbin/automount is now a script that sources in this file
#Depending on the variable AUTOFS, either AUTOFS or the old
#automount process will execute. The nfs.client start script 
#will also use this variable to start the appropriate process
#during the boot sequence. 
#AUTOFS= 0 - use the old automount process. 
#        1 - use the new AutoFS. 
#AUTOMOUNT_OPTIONS= - options to the AutoFS automount command
#AUTOMOUNTD_OPTIONS= - options to the AutoFS automountd daemon 
# 
#The AUTOMOUNT flag still needs to be set for either the old
#automount or new AutoFS to be started by the nfs.client script. 
# 
AUTOFS=0 
AUTOMOUNT_OPTIONS="" 
AUTOMOUNTD_OPTIONS=""

Manpages

A new manpage, automountd(1M) is being provided that describes the AutoFS automount daemon.

The automount(1M) manpage has been modified to describe both the old Automount daemon functionality and the new AutoFS command functionality.

Additional Documentation

For more information on how to migrate to AutoFS, see Chapter 2 in the Installing and Administering NFS manual.

Obsolescence

The existing 11.0 automounter can be re-enabled if desired, by setting the AUTOFS variable to 0 or removing the AUTOFS variable from /etc/rc.config.d/nfsconf. In this configuration, automounter will not mount file systems via the NFS version 3 protocol.

Although all 11.0 patch bundles contain both AutoFS and automounter, AutoFS will replace automounter in the next release of HP-UX.