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| <h2 class="chapter">28 System Databases and Name Service Switch</h2> |
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| <!-- %MENU% Accessing system databases --> |
| <p><a name="index-Name-Service-Switch-3249"></a><a name="index-NSS-3250"></a><a name="index-databases-3251"></a> |
| 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., <samp><span class="file">/etc/passwd</span></samp>), 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 <a href="../jargon/frobnicate.html#frobnicate">frobnicate</a>). |
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| <p>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<!-- /@w -->. GNU C Library follows their name and calls this |
| scheme <dfn>Name Service Switch</dfn> (NSS). |
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| <p>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. |
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| <li><a accesskey="1" href="NSS-Basics.html#NSS-Basics">NSS Basics</a>: What is this NSS good for. |
| <li><a accesskey="2" href="NSS-Configuration-File.html#NSS-Configuration-File">NSS Configuration File</a>: Configuring NSS. |
| <li><a accesskey="3" href="NSS-Module-Internals.html#NSS-Module-Internals">NSS Module Internals</a>: How does it work internally. |
| <li><a accesskey="4" href="Extending-NSS.html#Extending-NSS">Extending NSS</a>: What to do to add services or databases. |
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