Network Information Service (NIS)

Purpose and Concepts
Networking has led to the introduction of an enormous number of different network applications,
which in turn has brought new qualities to computer use. The single host environment has been
replaced by multiple hosts, which offer their resources to users and create an almost unrestricted
working environment. However to make and maintain such a working environment, a certain level of administration is required; otherwise, everything becomes useless.

Multiple hosts in the network present multiple administrative points and require more attention and work to be provided. Can you imagine the network with several hundred computers in it and a newuser account to be opened on each of them; or maybe a deletion or modification?

The Network Information Service (or System) − NIS, initially known as the Yellow Pages, is an
administrative database that enables a central control over a group of hosts (computers) that belong to the same, so−called NIS domain. NIS converts important administrative files into a database that can be queried over the network. This ensures that all hosts in the NIS domain have access to the very same administrative databases, which can then be centrally maintained. In NIS terminology, the databases are called NIS maps; they are all created at the single host, the NIS master server, and made accessible through the network to all hosts in the NIS domain — the NIS clients.
Any modification of an administrative file at the NIS master server can be easily transferred to an NIS map, and immediately made transparent to all other hosts. Since the number of NIS hosts could be very large, the benefit of a centralized administration is obvious: instead of repeating the same administrative task dozens, or even hundreds, of times, everything has to be done only once.
Theconsistency of the data is guaranteed and achieved in an optimal way. In addition, a sufficient
flexibility in administering individual hosts is preserved; NIS enables a selective approach to all
administrative issues.

NIS is Sun Microsystems' "baby," and it was a very successful product, first implemented on the
SunOS platform. Despite some inherent security problems, other UNIX vendors quickly adopted
NIS. Today NIS is a standard part of any UNIX installation. Sun Microsystems later released a new version of the Network Information System, known as NIS+. This was a new product for the same purpose, but definitely a different software package. The basic idea has been to improve the older product with the preserved compatibility. Unfortunately things do not always happen as expected.
The new product has not been so successful, and Solaris is practically the only UNIX flavor that
implemented it. Neither of the main UNIX players followed this path. Chances for some future
comeback of NIS+ are also cumbersome. Today it seems that another product, LDAP, is the most serious candidate to replace NIS.

LDAP stands for Lightweight Directory Access Protocol and presents a project to provide global
directory services over the Internet in an easier way. The idea is to obtain different types of
information from distributed databases spread all over the Internet (like e−mail addresses, phone numbers, etc.). Each "individual" LDAP server would manage its own database about its own community.
Individual servers will then be hierarchically merged, making needed information
accessible worldwide. The concept of LDAP is quite close to the DNS concept; this is not strange,
bearing in mind their similarities and the fact that DNS has been going on so successfully for quite a long time. LDAP was specified in the RFC−1777. LDAP mechanisms could also be used to
distribute administrative data, of course in a slightly more restrictive way. The existing RFC−2307 with the title "An Approach for Using LDAP as a Network Information Service" indicates such a tendency.