Editing Network Information Service (section)

{{Short description|Directory service protocol from Sun Microsystems}}
{{more citations needed|date=January 2019}}
The '''Network Information Service''', or '''NIS''' (originally called '''Yellow Pages''' or '''YP'''), is a [[client–server]] [[directory service]] [[protocol (computing)|protocol]] for [[Distributed computing|distributing]] [[system configuration]] data such as [[User (computing)|user]] and [[host name]]s between [[computer]]s on a [[computer network]]. [[Sun Microsystems]] developed the NIS; the technology is [[Software license|licensed]] to virtually all other [[Unix]] vendors.

Because [[British Telecom]] PLC owned the name "[[Yellow Pages]]" as a registered [[trademark]] in the [[United Kingdom]] for its paper-based, commercial [[telephone directory]], Sun changed the name of its system to NIS, though all the commands and functions still start with "yp".<ref>{{cite book|url=https://books.google.com/books?id=daks78g9Pg0C&pg=PA151|title=Automating System Administration with Perl: Tools to Make You More Efficient|author=David N. Blank-Edelman|publisher=[[O'Reilly Media]]|isbn=9780596555634|year=2009|page=151}}</ref>

A NIS/YP system maintains and distributes a central directory of user and group information, hostnames, e-mail aliases and other text-based tables of information in a computer network. For example, in a common [[Unix|UNIX]] environment, the list of users for [[Identification (information)|identification]] is placed in {{mono|[[Passwd (file)|/etc/passwd]]}} and secret [[authentication]] [[Cryptographic hash function|hashes]] in {{mono|/etc/shadow}}. NIS adds another "global" user list which is used for identifying users on any [[Client (computing)|client]] of the NIS domain.

Administrators have the ability to configure NIS to serve password data to outside processes to authenticate users using various versions of the Unix [[Crypt (C)|crypt(3)]] hash algorithms.  However, in such cases, any NIS(0307) client can retrieve the entire password database for offline inspection.