163 lines
4.5 KiB
HTML
163 lines
4.5 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of NSS</TITLE>
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</HEAD><BODY>
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<H1>NSS</H1>
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Section: Linux Programmer's Manual (5)<BR>Updated: 2013-02-13<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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nss - Name Service Switch configuration file
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<A NAME="lbAC"> </A>
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<H2>DESCRIPTION</H2>
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Each call to a function which retrieves data from a system database
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like the password or group database is handled by the Name Service
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Switch implementation in the GNU C library.
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The various services
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provided are implemented by independent modules, each of which
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naturally varies widely from the other.
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<P>
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The default implementations coming with the GNU C library are by
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default conservative and do not use unsafe data.
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This might be very costly in some situations, especially when the databases
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are large.
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Some modules allow the system administrator to request
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taking shortcuts if these are known to be safe.
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It is then the system administrator's responsibility to ensure the assumption
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is correct.
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<P>
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There are other modules where the implementation changed over time.
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If an implementation used to sacrifice speed for memory consumption,
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it might create problems if the preference is switched.
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<P>
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The
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<I>/etc/default/nss</I>
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file contains a number of variable assignments.
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Each variable controls the behavior of one or more
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NSS modules.
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White spaces are ignored.
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Lines beginning with '#'
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are treated as comments.
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<P>
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The variables currently recognized are:
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<DL COMPACT>
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<DT id="1"><B>NETID_AUTHORITATIVE =</B> <I>TRUE</I>|<I>FALSE</I><DD>
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If set to TRUE, the NIS backend for the
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<B><A HREF="/cgi-bin/man/man2html?3+initgroups">initgroups</A></B>(3)
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function will accept the information
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from the
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<I>netid.byname</I>
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NIS map as authoritative.
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This can speed up the function significantly if the
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<I>group.byname</I>
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map is large.
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The content of the
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<I>netid.byname</I>
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map is used <B>as is</B>.
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The system administrator has to make sure it is correctly generated.
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<DT id="2"><B>SERVICES_AUTHORITATIVE =</B> <I>TRUE</I>|<I>FALSE</I><DD>
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If set to TRUE, the NIS backend for the
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<B><A HREF="/cgi-bin/man/man2html?3+getservbyname">getservbyname</A></B>(3)
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and
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<B><A HREF="/cgi-bin/man/man2html?3+getservbyname_r">getservbyname_r</A></B>(3)
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functions will assume that the
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<I>services.byservicename</I>
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NIS map exists and is authoritative, particularly
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that it contains both keys with /proto and without /proto for both
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primary service names and service aliases.
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The system administrator has to make sure it is correctly generated.
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<DT id="3"><B>SETENT_BATCH_READ =</B> <I>TRUE</I>|<I>FALSE</I><DD>
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If set to TRUE, the NIS backend for the
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<B><A HREF="/cgi-bin/man/man2html?3+setpwent">setpwent</A></B>(3)
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and
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<B><A HREF="/cgi-bin/man/man2html?3+setgrent">setgrent</A></B>(3)
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functions will read the entire database at once and then
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hand out the requests one by one from memory with every corresponding
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<B><A HREF="/cgi-bin/man/man2html?3+getpwent">getpwent</A></B>(3)
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or
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<B><A HREF="/cgi-bin/man/man2html?3+getgrent">getgrent</A></B>(3)
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call respectively.
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Otherwise, each
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<B><A HREF="/cgi-bin/man/man2html?3+getpwent">getpwent</A></B>(3)
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or
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<B><A HREF="/cgi-bin/man/man2html?3+getgrent">getgrent</A></B>(3)
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call might result in a network communication with the server to get
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the next entry.
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</DL>
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<A NAME="lbAD"> </A>
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<H2>FILES</H2>
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<I>/etc/default/nss</I>
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<A NAME="lbAE"> </A>
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<H2>EXAMPLE</H2>
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The default configuration corresponds to the following configuration file:
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<P>
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NETID_AUTHORITATIVE=FALSE
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SERVICES_AUTHORITATIVE=FALSE
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SETENT_BATCH_READ=FALSE
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<A NAME="lbAF"> </A>
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<H2>SEE ALSO</H2>
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<I>nsswitch.conf</I>
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<A NAME="lbAG"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="4"><A HREF="#lbAB">NAME</A><DD>
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<DT id="5"><A HREF="#lbAC">DESCRIPTION</A><DD>
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<DT id="6"><A HREF="#lbAD">FILES</A><DD>
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<DT id="7"><A HREF="#lbAE">EXAMPLE</A><DD>
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<DT id="8"><A HREF="#lbAF">SEE ALSO</A><DD>
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<DT id="9"><A HREF="#lbAG">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:04 GMT, March 31, 2021
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</BODY>
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</HTML>
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