source: BOOK/final-system/common/glibc.xml@ c70f11b

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<sect1 id="ch-system-glibc" role="wrap">
  <?dbhtml filename="glibc.html"?>

  <title>Glibc-&glibc-version;</title>

  <indexterm zone="ch-system-glibc">
    <primary sortas="a-Glibc">Glibc</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The Glibc package contains the main C library. This library provides
    the basic routines for allocating memory, searching directories, opening and
    closing files, reading and writing files, string handling, pattern matching,
    arithmetic, and so on.</para>

  </sect2>

  <sect2 role="installation">
    <title>Installation of Glibc</title>

    <note os="z">
      <para>Some packages outside of CLFS suggest installing GNU libiconv in
      order to translate data from one encoding to another. The project's
      home page (<ulink url="http://www.gnu.org/software/libiconv/"/>) says
      <quote>This library provides an <function>iconv()</function>
      implementation, for use on systems which don't have one, or whose
      implementation cannot convert from/to Unicode.</quote> Glibc provides
      an <function>iconv()</function> implementation and can convert from/to
      Unicode, therefore libiconv is not required on a CLFS system.</para>
    </note>

    <para os="b">The Glibc build system is self-contained and will install
    perfectly, even though the compiler specs file and linker are still
    pointing at <filename class="directory">/tools</filename>. The specs
    and linker cannot be adjusted before the Glibc install because the
    Glibc Autoconf tests would give false results and defeat the goal
    of achieving a clean build.</para>

    <para os="p1">The following patches merges all updates from the &glibc-version; Branch
    from the Glibc developers:</para>

<screen os="p2"><userinput>patch -Np1 -i ../&glibc-branch_update-patch;</userinput></screen>

    <para os="c">The following patch fixes an issue that can
    cause <command>localdef</command> to segfault:</para>

<screen os="d"><userinput>patch -Np1 -i ../&glibc-localedef_segfault-patch;</userinput></screen>

    <para os="e">The Glibc documentation recommends building Glibc outside of the
    source directory in a dedicated build directory:</para>

<screen os="f"><userinput>mkdir -v ../glibc-build
cd ../glibc-build</userinput></screen>

    <para os="g">Prepare Glibc for compilation:</para>

<screen os="h"><userinput>../glibc-&glibc-version;/configure --prefix=/usr \
    --disable-profile --enable-add-ons --enable-kernel=2.6.0 \
    --libexecdir=/usr/lib/glibc</userinput></screen>

    <variablelist os="i">
      <title>The meaning of the new configure option:</title>

      <varlistentry>
        <term><parameter>--libexecdir=/usr/lib/glibc</parameter></term>
        <listitem>
          <para>This changes the location of the <command>pt_chown</command>
          program from its default of <filename
          class="directory">/usr/libexec</filename> to <filename
          class="directory">/usr/lib/glibc</filename>.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para os="j">Compile the package:</para>

<screen os="k"><userinput>make</userinput></screen>

    <important os="l">
      <para>The test suite for Glibc is considered critical.
      Do not skip it under any circumstance.</para>
    </important>

    <para os="m">Test the results:</para>

<!-- items n,o,p no longer the master, use x86_64 which has no failures -->

<screen os="n"><userinput>make -k check &gt;glibc-check-log 2&gt;&amp;1 ; grep Error glibc-check-log</userinput></screen>

    <para os="o">The Glibc test suite is highly dependent on certain functions of
    the host system, in particular the kernel. The posix/annexc test normally fails
    and you should see <literal>Error 1 (ignored)</literal> in the output. Apart
    from this, the Glibc test suite is always expected to pass. However, in certain
    circumstances, some failures are unavoidable. If a test fails because of a missing
    program (or missing symbolic link), or a segfault, you will see an error code
    greater than 127 and the details will be in the log. More commonly, tests will
    fail with <literal>Error 2</literal> - for these, the contents of the corresponding
    <filename>.out</filename> file, e.g. <filename>posix/annexc.out</filename> may be
    informative. Here is a list of the most common issues:</para>

    <itemizedlist os="p">
      <listitem>
        <para>The <emphasis>math</emphasis> tests sometimes fail.
        Certain optimization settings are known to be a
        factor here.</para>
      </listitem>
      <listitem>
        <para>If you have mounted the CLFS partition with the
        <parameter>noatime</parameter> option, the <emphasis>atime</emphasis> test
        will fail. As mentioned in <xref linkend="ch-partitioning-mounting"/>,
        do not use the <parameter>noatime</parameter> option while building
        CLFS.</para>
      </listitem>
      <listitem>
        <para>When running on older and slower hardware, some tests
        can fail because of test timeouts being exceeded.</para>
      </listitem>
    </itemizedlist>

    <para os="q">Though it is a harmless message, the install stage of Glibc will
    complain about the absence of <filename>/etc/ld.so.conf</filename>.
    Prevent this warning with:</para>

<screen os="r"><userinput>touch /etc/ld.so.conf</userinput></screen>

    <para os="s">Install the package:</para>

<screen os="t"><userinput>make install</userinput></screen>

  </sect2>

  <sect2 id="i18n-glibc" role="configuration">
    <title>Internationalization</title>

    <para>The locales that can make the system respond in a different
    language were not installed by the above command. Install them
    with:</para>

<screen><userinput>make localedata/install-locales</userinput></screen>

    <para>To save time, an alternative to running the previous command (which
    generates and installs every locale listed in the
    glibc-&glibc-version;/localedata/SUPPORTED file) is to install only
    those locales that are wanted and needed. This can be achieved by using
    the <command>localedef</command> command. Information on this command is
    located in the <filename>INSTALL</filename> file in the Glibc source.
    However, there are a number of locales that are essential in order for the
    tests of future packages to pass, in particular, the
    <emphasis>libstdc++</emphasis> tests from GCC. The following instructions,
    instead of the <parameter>install-locales</parameter> target used above,
    will install the minimum set of locales necessary for the tests to run
    successfully:</para>

<screen role="nodump"><userinput>mkdir -pv /usr/lib/locale
localedef -i cs_CZ -f UTF-8 cs_CZ.UTF-8
localedef -i de_DE -f ISO-8859-1 de_DE
localedef -i de_DE@euro -f ISO-8859-15 de_DE@euro
localedef -i en_HK -f ISO-8859-1 en_HK
localedef -i en_PH -f ISO-8859-1 en_PH
localedef -i en_US -f ISO-8859-1 en_US
localedef -i es_MX -f ISO-8859-1 es_MX
localedef -i fa_IR -f UTF-8 fa_IR
localedef -i fr_FR -f ISO-8859-1 fr_FR
localedef -i fr_FR@euro -f ISO-8859-15 fr_FR@euro
localedef -i it_IT -f ISO-8859-1 it_IT
localedef -i ja_JP -f EUC-JP ja_JP</userinput></screen>

    <para>Some locales installed by the <command>make
    localedata/install-locales</command> command above are not properly
    supported by some applications that are in the CLFS and BLFS books. Because
    of the various problems that arise due to application programmers making
    assumptions that break in such locales, CLFS should not be used in locales
    that utilize multibyte character sets (including UTF-8) or right-to-left
    writing order.  Numerous unofficial and unstable patches are required to
    fix these problems, and it has been decided by the CLFS developers not to
    support such complex locales at this time. This applies to the ja_JP and
    fa_IR locales as well&mdash;they have been installed only for GCC and
    Gettext tests to pass, and the <command>watch</command> program (part of
    the Procps package) does not work properly in them. Various attempts to
    circumvent these restrictions are documented in internationalization-related
    hints.</para>

  </sect2>

  <sect2 id="conf-glibc" role="configuration">
    <title>Configuring Glibc</title>

    <indexterm zone="conf-glibc">
      <primary sortas="e-/etc/nsswitch.conf">/etc/nsswitch.conf</primary>
    </indexterm>

    <indexterm zone="conf-glibc">
      <primary sortas="e-/etc/localtime">/etc/localtime</primary>
    </indexterm>

    <para>The <filename>/etc/nsswitch.conf</filename> file needs to be created
    because, although Glibc provides defaults when this file is missing or
    corrupt, the Glibc defaults do not work well in a networked environment.
    The time zone also needs to be configured.</para>

    <para>Create a new file <filename>/etc/nsswitch.conf</filename> by running
    the following:</para>

<screen><userinput>cat &gt; /etc/nsswitch.conf &lt;&lt; "EOF"
<literal># Begin /etc/nsswitch.conf

passwd: files
group: files
shadow: files

hosts: files dns
networks: files

protocols: files
services: files
ethers: files
rpc: files

# End /etc/nsswitch.conf</literal>
EOF</userinput></screen>

    <para>To determine the local time zone, run the following script:</para>

<screen role="nodump"><userinput>tzselect</userinput></screen>

    <para>After answering a few questions about the location, the script will
    output the name of the time zone (e.g., <emphasis>EST5EDT</emphasis> or
    <emphasis>Canada/Eastern</emphasis>). Then create the
    <filename>/etc/localtime</filename> file by running:</para>

<screen><userinput>cp -v --remove-destination /usr/share/zoneinfo/<replaceable>[xxx]</replaceable> \
    /etc/localtime</userinput></screen>

    <para>Replace <replaceable>[xxx]</replaceable> with the name of the time zone
    that <command>tzselect</command> provided (e.g., Canada/Eastern).</para>

    <variablelist>
      <title>The meaning of the cp option:</title>

      <varlistentry>
        <term><parameter>--remove-destination</parameter></term>
        <listitem>
          <para>This is needed to force removal of the already existing symbolic
          link. The reason for copying the file instead of using a symlink is to
          cover the situation where <filename class="directory">/usr</filename>
          is on a separate partition. This could be important when booted into
          single user mode.</para>
        </listitem>
      </varlistentry>
    </variablelist>

  </sect2>

  <sect2 id="conf-ld" role="configuration">
    <title>Configuring The Dynamic Loader</title>

    <indexterm zone="conf-ld">
      <primary sortas="e-/etc/ld.so.conf">/etc/ld.so.conf</primary>
    </indexterm>

    <para>By default, the dynamic loader (<filename
    class="libraryfile">/lib/ld-linux.so.2</filename>) searches through
    <filename class="directory">/lib</filename> and <filename
    class="directory">/usr/lib</filename> for dynamic libraries that are
    needed by programs as they are run. However, if there are libraries in
    directories other than <filename class="directory">/lib</filename> and
    <filename class="directory">/usr/lib</filename>, these need to be
    added to the <filename>/etc/ld.so.conf</filename> file in order
    for the dynamic loader to find them. Two directories that are commonly
    known to contain additional libraries are <filename
    class="directory">/usr/local/lib</filename> and <filename
    class="directory">/opt/lib</filename>, so add those directories to the
    dynamic loader's search path.</para>

    <para>Create a new file <filename>/etc/ld.so.conf</filename> by running the
    following:</para>

<screen><userinput>cat &gt; /etc/ld.so.conf &lt;&lt; "EOF"
<literal># Begin /etc/ld.so.conf

/usr/local/lib
/opt/lib

# End /etc/ld.so.conf</literal>
EOF</userinput></screen>

  </sect2>

  <sect2 id="contents-glibc" role="content">
    <title>Contents of Glibc</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed libraries</segtitle>

      <seglistitem>
        <seg>catchsegv, gencat, getconf, getent, iconv, iconvconfig, ldconfig,
        ldd, lddlibc4, locale, localedef, mtrace, nscd,
        pcprofiledump, pt_chown, rpcgen, rpcinfo, sln, sprof, tzselect, xtrace,
        zdump, and zic</seg>
        <seg>ld.so, libBrokenLocale.[a,so], libSegFault.so, libanl.[a,so],
        libbsd-compat.a, libc.[a,so], libcrypt.[a,so], libdl.[a,so], libg.a,
        libieee.a, libm.[a,so], libmcheck.a, libmemusage.so, libnsl.a,
        libnss_compat.so, libnss_dns.so, libnss_files.so, libnss_hesiod.so,
        libnss_nis.so, libnss_nisplus.so, libpcprofile.so, libpthread.[a,so],
        libresolv.[a,so], librpcsvc.a, librt.[a,so], libthread_db.so, and
        libutil.[a,so]</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="catchsegv">
        <term><command>catchsegv</command></term>
        <listitem>
          <para>Can be used to create a stack trace when a program
          terminates with a segmentation fault</para>
          <indexterm zone="ch-system-glibc catchsegv">
            <primary sortas="b-catchsegv">catchsegv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gencat">
        <term><command>gencat</command></term>
        <listitem>
          <para>Generates message catalogues</para>
          <indexterm zone="ch-system-glibc gencat">
            <primary sortas="b-gencat">gencat</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="getconf">
        <term><command>getconf</command></term>
        <listitem>
          <para>Displays the system configuration values for file system specific
          variables</para>
          <indexterm zone="ch-system-glibc getconf">
            <primary sortas="b-getconf">getconf</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="getent">
        <term><command>getent</command></term>
        <listitem>
          <para>Gets entries from an administrative database</para>
          <indexterm zone="ch-system-glibc getent">
            <primary sortas="b-getent">getent</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="iconv">
        <term><command>iconv</command></term>
        <listitem>
          <para>Performs character set conversion</para>
          <indexterm zone="ch-system-glibc iconv">
            <primary sortas="b-iconv">iconv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="iconvconfig">
        <term><command>iconvconfig</command></term>
        <listitem>
          <para>Creates fastloading <command>iconv</command> module configuration
          files</para>
          <indexterm zone="ch-system-glibc iconvconfig">
            <primary sortas="b-iconvconfig">iconvconfig</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="ldconfig">
        <term><command>ldconfig</command></term>
        <listitem>
          <para>Configures the dynamic linker runtime bindings</para>
          <indexterm zone="ch-system-glibc ldconfig">
            <primary sortas="b-ldconfig">ldconfig</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="ldd">
        <term><command>ldd</command></term>
        <listitem>
          <para>Reports which shared libraries are required
          by each given program or shared library</para>
          <indexterm zone="ch-system-glibc ldd">
            <primary sortas="b-ldd">ldd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="lddlibc4">
        <term><command>lddlibc4</command></term>
        <listitem>
          <para>Assists <command>ldd</command> with object files</para>
          <indexterm zone="ch-system-glibc lddlibc4">
            <primary sortas="b-lddlibc4">lddlibc4</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="locale">
        <term><command>locale</command></term>
        <listitem>
          <para>Tells the compiler to enable or disable the use of POSIX locales
          for built-in operations</para>
          <indexterm zone="ch-system-glibc locale">
            <primary sortas="b-locale">locale</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="localedef">
        <term><command>localedef</command></term>
        <listitem>
          <para>Compiles locale specifications</para>
          <indexterm zone="ch-system-glibc localedef">
            <primary sortas="b-localedef">localedef</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="mtrace">
        <term><command>mtrace</command></term>
        <listitem>
          <para>Reads and interprets a memory trace file and
          displays a summary in human-readable format</para>
          <indexterm zone="ch-system-glibc mtrace">
            <primary sortas="b-mtrace">mtrace</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="nscd">
        <term><command>nscd</command></term>
        <listitem>
          <para>A daemon that provides a cache for the most common name
          service requests</para>
          <indexterm zone="ch-system-glibc nscd">
            <primary sortas="b-nscd">nscd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="pcprofiledump">
        <term><command>pcprofiledump</command></term>
        <listitem>
          <para>Dumps information generated by PC profiling</para>
          <indexterm zone="ch-system-glibc pcprofiledump">
            <primary sortas="b-pcprofiledump">pcprofiledump</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="pt_chown">
        <term><command>pt_chown</command></term>
        <listitem>
          <para>A helper program for <command>grantpt</command> to set the owner,
          group and access permissions of a slave pseudo terminal</para>
          <indexterm zone="ch-system-glibc pt_chown">
            <primary sortas="b-pt_chown">pt_chown</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="rpcgen">
        <term><command>rpcgen</command></term>
        <listitem>
          <para>Generates C code to implement the Remote Procecure Call (RPC)
          protocol</para>
          <indexterm zone="ch-system-glibc rpcgen">
            <primary sortas="b-rpcgen">rpcgen</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="rpcinfo">
        <term><command>rpcinfo</command></term>
        <listitem>
          <para>Makes an RPC call to an RPC server</para>
          <indexterm zone="ch-system-glibc rpcinfo">
            <primary sortas="b-rpcinfo">rpcinfo</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="sln">
        <term><command>sln</command></term>
        <listitem>
          <para>A statically linked program that creates symbolic links</para>
          <indexterm zone="ch-system-glibc sln">
            <primary sortas="b-sln">sln</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="sprof">
        <term><command>sprof</command></term>
        <listitem>
          <para>Reads and displays shared object profiling data</para>
          <indexterm zone="ch-system-glibc sprof">
            <primary sortas="b-sprof">sprof</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="tzselect">
        <term><command>tzselect</command></term>
        <listitem>
          <para>Asks the user about the location of the
          system and reports the corresponding time zone description</para>
          <indexterm zone="ch-system-glibc tzselect">
            <primary sortas="b-tzselect">tzselect</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="xtrace">
        <term><command>xtrace</command></term>
        <listitem>
          <para>Traces the execution of a program by
          printing the currently executed function</para>
          <indexterm zone="ch-system-glibc xtrace">
            <primary sortas="b-xtrace">xtrace</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="zdump">
        <term><command>zdump</command></term>
        <listitem>
          <para>The time zone dumper</para>
          <indexterm zone="ch-system-glibc zdump">
            <primary sortas="b-zdump">zdump</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="zic">
        <term><command>zic</command></term>
        <listitem>
          <para>The time zone compiler</para>
          <indexterm zone="ch-system-glibc zic">
            <primary sortas="b-zic">zic</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="ld.so">
        <term><filename class="libraryfile">ld.so</filename></term>
        <listitem>
          <para>The helper program for shared library executables</para>
          <indexterm zone="ch-system-glibc ld.so">
            <primary sortas="c-ld.so">ld.so</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libBrokenLocale">
        <term><filename class="libraryfile">libBrokenLocale</filename></term>
        <listitem>
          <para>Used by programs, such as Mozilla, to solve broken locales</para>
          <indexterm zone="ch-system-glibc libBrokenLocale">
            <primary sortas="c-libBrokenLocale">libBrokenLocale</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libSegFault">
        <term><filename class="libraryfile">libSegFault</filename></term>
        <listitem>
          <para>The segmentation fault signal handler</para>
          <indexterm zone="ch-system-glibc libSegFault">
            <primary sortas="c-libSegFault">libSegFault</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libanl">
        <term><filename class="libraryfile">libanl</filename></term>
        <listitem>
          <para>An asynchronous name lookup library</para>
          <indexterm zone="ch-system-glibc libanl">
            <primary sortas="c-libanl">libanl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libbsd-compat">
        <term><filename class="libraryfile">libbsd-compat</filename></term>
        <listitem>
          <para>Provides the portability needed
          in order to run certain Berkey Software Distribution (BSD) programs
          under Linux</para>
          <indexterm zone="ch-system-glibc libbsd-compat">
            <primary sortas="c-libbsd-compat">libbsd-compat</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libc">
        <term><filename class="libraryfile">libc</filename></term>
        <listitem>
          <para>The main C library</para>
          <indexterm zone="ch-system-glibc libc">
            <primary sortas="c-libc">libc</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libcrypt">
        <term><filename class="libraryfile">libcrypt</filename></term>
        <listitem>
          <para>The cryptography library</para>
          <indexterm zone="ch-system-glibc libcrypt">
            <primary sortas="c-libcrypt">libcrypt</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libdl">
        <term><filename class="libraryfile">libdl</filename></term>
        <listitem>
          <para>The dynamic linking interface library</para>
          <indexterm zone="ch-system-glibc libdl">
            <primary sortas="c-libdl">libdl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libg">
        <term><filename class="libraryfile">libg</filename></term>
        <listitem>
          <para>A runtime library for <command>g++</command></para>
          <indexterm zone="ch-system-glibc libg">
            <primary sortas="c-libg">libg</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libieee">
        <term><filename class="libraryfile">libieee</filename></term>
        <listitem>
          <para>The Institute of Electrical and Electronic Engineers (IEEE)
          floating point library</para>
          <indexterm zone="ch-system-glibc libieee">
            <primary sortas="c-libieee">libieee</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libm">
        <term><filename class="libraryfile">libm</filename></term>
        <listitem>
          <para>The mathematical library</para>
          <indexterm zone="ch-system-glibc libm">
            <primary sortas="c-libm">libm</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libmcheck">
        <term><filename class="libraryfile">libmcheck</filename></term>
        <listitem>
          <para>Contains code run at boot</para>
          <indexterm zone="ch-system-glibc libmcheck">
            <primary sortas="c-libmcheck">libmcheck</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libmemusage">
        <term><filename class="libraryfile">libmemusage</filename></term>
        <listitem>
          <para>Used by <command>memusage</command> (included in Glibc, but
          not built in a base CLFS system as it has additional dependencies)
          to help collect information about the memory usage of a program</para>
          <indexterm zone="ch-system-glibc libmemusage">
            <primary sortas="c-libmemusage">libmemusage</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libnsl">
        <term><filename class="libraryfile">libnsl</filename></term>
        <listitem>
          <para>The network services library</para>
          <indexterm zone="ch-system-glibc libnsl">
            <primary sortas="c-libnsl">libnsl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libnss">
        <term><filename class="libraryfile">libnss</filename></term>
        <listitem>
          <para>The Name Service Switch libraries, containing functions for
          resolving host names, user names, group names, aliases, services,
          protocols, etc.</para>
          <indexterm zone="ch-system-glibc libnss">
            <primary sortas="c-libnss">libnss</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libpcprofile">
        <term><filename class="libraryfile">libpcprofile</filename></term>
        <listitem>
          <para>Contains profiling functions used to track the amount of CPU
          time spent in specific source code lines</para>
          <indexterm zone="ch-system-glibc libpcprofile">
            <primary sortas="c-libpcprofile">libpcprofile</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libpthread">
        <term><filename class="libraryfile">libpthread</filename></term>
        <listitem>
          <para>The POSIX threads library</para>
          <indexterm zone="ch-system-glibc libpthread">
            <primary sortas="c-libpthread">libpthread</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libresolv">
        <term><filename class="libraryfile">libresolv</filename></term>
        <listitem>
          <para>Contains functions for creating, sending, and interpreting
          packets to the Internet domain name servers</para>
          <indexterm zone="ch-system-glibc libresolv">
            <primary sortas="c-libresolv">libresolv</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="librpcsvc">
        <term><filename class="libraryfile">librpcsvc</filename></term>
        <listitem>
          <para>Contains functions providing miscellaneous RPC services</para>
          <indexterm zone="ch-system-glibc librpcsvc">
            <primary sortas="c-librpcsvc">librpcsvc</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="librt">
        <term><filename class="libraryfile">librt</filename></term>
        <listitem>
          <para>Contains functions providing most of the interfaces specified by
          the POSIX.1b Realtime Extension</para>
          <indexterm zone="ch-system-glibc librt">
            <primary sortas="c-librt">librt</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libthread_db">
        <term><filename class="libraryfile">libthread_db</filename></term>
        <listitem>
          <para>Contains functions useful for
          building debuggers for multi-threaded programs</para>
          <indexterm zone="ch-system-glibc libthread_db">
            <primary sortas="c-libthread_db">libthread_db</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libutil">
        <term><filename class="libraryfile">libutil</filename></term>
        <listitem>
          <para>Contains code for <quote>standard</quote> functions used in
          many different Unix utilities</para>
          <indexterm zone="ch-system-glibc libutil">
            <primary sortas="c-libutil">libutil</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>