Installation guide

252 Chapter 17. Network File System (NFS)
The options area specifies how the file system is to be mounted. For example, if the options area
states rw,suid on a particular mount, the exported file system will be mounted read-write and the
user and group ID set by the server will be used. Note, parentheses are not to be used here. For more
mount options, see Section 17.3.3.
17.3.2. autofs
One drawback to using /etc/fstab is that, regardless of how much you use that mounted file system,
your system must dedicate resources to keep that mount in place. This is not a problem with one or
two mounts, but when your system is maintaining mounts to a dozen systems at one time, overall
system performance can suffer. An alternative to /etc/fstab is to use the kernel-based automount
utility, which will mount and unmount NFS file systems automatically, saving resources.
The autofs script, located in /etc/rc.d/init.d, is used to control automount through the
/etc/auto.master primary configuration file. While automount can be specified on the
command line, it is more convenient to specify the mount points, hostname, exported directory, and
options in a set of files rather than typing them all by hand. By running autofs as a service that starts
and stops in designated runlevels, the mount configurations in the various files can be automatically
implemented. In order to use autofs, you must have the autofs RPM installed on your system.
The autofs configuration files are arranged in a parent-child relationship. A main configuration file
(/etc/auto.master) refers mount points on your system that are linked to a particular map type,
which take the form of other configuration files, programs, NIS maps, and other less common mount
methods. The auto.master file contains lines referring to each of these mount points, organized like
this:
mount-point map-type
The mount-point indicates where the device or exported file system should mount on your local
file system. The
map-type relates to the way in which the mount point will be mounted. The
most common method for auto mounting NFS exports is to use a file as the map type for the particular
mount point. The map file, usually named auto. mount-point , where mount-point is the
mount point designated in auto.master, contains lines that look like this:
directory mount-options host : exported-file-system
The directory refers to the directory within the mount point where the exported file system
should be mounted. Much like a standard mount command, the host exporting the file system, as
well as the file system being exported, are required in the host : exported-file system
section. To specify particular options to be used when mounting the exported file system, place them
in the
mount-options section, separated by commas. For NFS mounts that use autofs, you
should definitely place -fstype=nfs in the
mount-options section, at a minimum.
While autofs configuration files can be used for a variety of mounts to many types of devices and file
systems, they are particularly useful in creating NFS mounts. For example, some organizations store a
user’s /home directory on a central server via an NFS share. Then, they configure the auto.master
file on each of the workstations to point to an auto.home file containing the specifics for how to
mount the /home directory via NFS. This allows the user to access personal data and configuration
files in their /home directory by logging in anywhere on the internal network. The auto.master file
in this situation would look similar to this:
/home /etc/auto.home
This sets up the /home mount point on the local system to be configured by the /etc/auto.home
file, which may look similar to this:
* -fstype=nfs,soft,intr,rsize=8192,wsize=8192,nosuid server.domain.com:/home/&