Managing NFS and NIS
1
Preface
Twenty years ago, most computer centers had a few large computers shared by several
hundred users. The "computing environment" was usually a room containing dozens of
terminals. All users worked in the same place, with one set of disks, one user account
information file, and one view of all resources. Today, local area networks have made
terminal rooms much less common. Now, a "computing environment" almost always refers to
distributed computing, where users have personal desktop machines, and shared resources are
provided by special-purpose systems such as file, computer, and print servers. Each desktop
requires redundant configuration files, including user information, network host addresses,
and local and shared remote filesystem information.
A mechanism to provide consistent access to all files and configuration information ensures
that all users have access to the "right" machines, and that once they have logged in they will
see a set of files that is both familiar and complete. This consistency must be provided in a
way that is transparent to the users; that is, a user should not know that a filesystem is located
on a remote fileserver. The transparent view of resources must be consistent across all
machines and also consistent with the way things work in a non-networked environment. In a
networked computing environment, it's usually up to the system administrator to manage the
machines on the network (including centralized servers) as well as the network itself.
Managing the network means ensuring that the network is transparent to users rather than an
impediment to their work.
The Network File System (NFS) and the Network Information Service (NIS)
[1]
provide
mechanisms for solving "consistent and transparent" access problems. The NFS and NIS
protocols were developed by Sun Microsystems and are now licensed to hundreds of vendors
and universities, not to mention dozens of implementations from the published NFS and NFS
specifications. NIS centralizes commonly replicated configuration files, such as the password
file, on a single host. It eliminates duplicate copies of user and system information and allows
the system administrator to make changes from one place. NFS makes remote filesystems
appear to be local, as if they were on disks attached to the local host. With NFS, all machines
can share a single set of files, eliminating duplicate copies of files on different machines in the
network. Using NFS and NIS together greatly simplifies the management of various
combinations of machines, users, and filesystems.
[1]
NIS was formerly called the "Yellow Pages." While many commands and directory names retain the yp prefix, the formal name of the set of
services has been changed to avoid conflicting with registered trademarks.
NFS provides network and filesystem transparency because it hides the actual, physical
location of the filesystem. A user's files could be on a local disk, on a shared disk on a
fileserver, or even on a machine located across a wide-area network. As a user, you're most
content when you see the same files on all machines. Just having the files available, though,
doesn't mean that you can access them if your user information isn't correct. Missing or
inconsistent user and group information will break Unix file permission checking. This is
where NIS complements NFS, by adding consistency to the information used to build and
describe the shared filesystems. A user can sit down in front of any workstation in his or her
group that is running NIS and be reasonably assured that he or she can log in, find his or her
home directory, and access tools such as compilers, window systems, and publishing
packages. In addition to making life easier for the users, NFS and NIS simplify the tasks of
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