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244 Chapter 18. Network File System (NFS)

The options area speciﬁes how the ﬁlesystem is to be mounted. For example, if the options area

states rw,suid on a particular mount, the exported ﬁlesystem 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 18.3.3.

18.3.2. autofs

One drawback to using /etc/fstab is that, regardless of how much you use that mounted ﬁlesystem,

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 ﬁlesystems 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 ﬁlesystem should mount on your local

ﬁlesystem. 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-filesystem

The directory refers to the directory within the mount point where the exported ﬁlesystem

should be mounted. Much like a standard mount command, the host exporting the ﬁlesystem, as well

as the ﬁlesystem being exported, are required in the host : exported-filesystem section.

To specify particular options to be used when mounting the exported ﬁlesystem, 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 ﬁlesystems, they are particularly useful in creating NFS mounts. For example, some organiza-

tions 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/&

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