UNIX network services: Regarding NIS on UNIX systems, which single option best captures what NIS is and what it does?

Introduction / Context:
NIS (Network Information Service), historically known as Yellow Pages (YP), is a long-standing UNIX facility for sharing administrative data such as user accounts and groups across multiple systems. Knowing what NIS is—and is not—helps in distinguishing it from unrelated desktop or GUI technologies.

Given Data / Assumptions:

• NIS is a directory-like naming and lookup service for UNIX networks.
• It centralizes data like passwd, group, and other configuration maps.
• It is unrelated to graphical desktops or window managers.

Concept / Approach:
NIS provides centralized maps to simplify account management and authentication across a set of machines. It predates LDAP and modern directory services, but the conceptual role is similar: a shared source of truth for identity and configuration data. Documentation and command names (yp*) reflect its original “Yellow Pages” branding.

Step-by-Step Solution:

Verification / Alternative check:
Cross-verify with admin manuals: ypbind, ypcat, and ypwhich are standard NIS utilities; none relate to X Window managers. NIS maps include passwd.byname, group.byname, etc.

Why Other Options Are Wrong:
A only / B only: Incomplete because both are true. C: Mischaracterizes NIS entirely. None of the above: False because A and B are accurate.

Common Pitfalls:
Confusing NIS with LDAP/Active Directory; assuming NIS provides encryption or strong security by default (it does not). Modern deployments may favor LDAP/Kerberos for stronger security and scalability.

Final Answer:
Both A and B are correct.