The Name Service Switch (NSS) is a feature found in the standard C library of various Unix-like operating systems that connects a computer with a variety of sources of common configuration databases and name resolution mechanisms.
This file lists databases (such as passwd, shadow and group), and one or more sources for obtaining that information.
Examples for sources are files for local files, ldap for the Lightweight Directory Access Protocol, nis for the Network Information Service, nisplus for NIS+, dns for the Domain Name System (DNS), and wins for Windows Internet Name Service.
Sun engineers Thomas Maslen and Sanjay Dani were the first to design and implement the Name Service Switch.
Over the years, programmers ported the NSS configuration file with nearly identical implementations to many other operating systems including FreeBSD, NetBSD, Linux, HP-UX, IRIX and AIX[citation needed].