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The GNU C Library

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28. System Databases and Name Service Switch

Various functions in the C Library need to be configured to work correctly in the local environment. Traditionally, this was done by using files (e.g., `/etc/passwd'), but other nameservices (like the Network Information Service (NIS) and the Domain Name Service (DNS)) became popular, and were hacked into the C library, usually with a fixed search order (see section `frobnicate' in The Jargon File).

The GNU C Library contains a cleaner solution of this problem. It is designed after a method used by Sun Microsystems in the C library of Solaris 2. GNU C Library follows their name and calls this scheme Name Service Switch (NSS).

Though the interface might be similar to Sun's version there is no common code. We never saw any source code of Sun's implementation and so the internal interface is incompatible. This also manifests in the file names we use as we will see later.

28.1 NSS Basics  What is this NSS good for.
28.2 The NSS Configuration File  Configuring NSS.
28.3 NSS Module Internals  How does it work internally.
28.4 Extending NSS  What to do to add services or databases.

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