lfs-book/chapter06/glibc.xml

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

  <sect1info condition="script">
    <productname>glibc</productname>
    <productnumber>&glibc-version;</productnumber>
    <address>&glibc-url;</address>
  </sect1info>

  <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>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&glibc-ch6-sbu;</seg>
        <seg>&glibc-ch6-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

    <note><para>The Glibc build system is self-contained and will install
    perfectly, even though the compiler specs file and linker are still
    pointing to <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></note>

    <para>Some of the Glibc programs use non-FHS compilant
    <filename class="directory">/var/db</filename> directory to store
    their runtime data. Apply the following patch to make such programs
    store their runtime data in the FHS-compliant locations:</para>

<screen><userinput remap="pre">patch -Np1 -i ../&glibc-fhs-patch;</userinput></screen>

    <para>The Glibc documentation recommends building Glibc 
    in a dedicated build directory:</para>

<screen><userinput remap="pre">mkdir -v build
cd       build</userinput></screen>

    <para>Prepare Glibc for compilation:</para>

<screen><userinput remap="configure">../configure --prefix=/usr          \
             --enable-kernel=&min-kernel; \
             --enable-obsolete-rpc</userinput></screen>

    <para>Compile the package:</para>

<screen><userinput remap="make">make</userinput></screen>

    <important>
      <para>In this section, the test suite for Glibc is considered critical.
      Do not skip it under any circumstance.</para>
    </important>

    <para>Generally a few tests do not pass, but you can generally ignore
    any of the test failures listed below. Now test the build results:</para>

<screen><userinput remap="test">make check</userinput></screen>

    <para>You will probably see some test failures.  The Glibc test suite is
    somewhat dependent on the host system.  This is a list of the most common
    issues seen for this version of LFS:</para>

    <itemizedlist>

      <listitem>
        <para><emphasis>posix/tst-getaddrinfo4</emphasis> will always fail due
        to not having the necessary networking applications when the tests are
        run.</para>
      </listitem>

      <listitem>
        <para>The <emphasis>rt/tst-cputimer1</emphasis> and 
        <emphasis>rt/tst-cpuclock2</emphasis> tests have been known to
        fail.  The reason is not completely understood, but indications are
        that minor timing issues can trigger these failures.</para>
      </listitem>

      <listitem>
        <para>The math tests sometimes fail when running on
        systems where the CPU is not a relatively new Intel or
        AMD processor.</para>
      </listitem>

      <listitem>
        <para>The
        <emphasis>nptl/tst-thread-affinity-{pthread,pthread2,sched}</emphasis>
        tests may fail for reasons that have not been determined.  </para>
      </listitem>

      <listitem>
        <para>Other tests known to fail on some architectures are
        malloc/tst-malloc-usable and nptl/tst-cleanupx4. </para>
      </listitem>

    </itemizedlist>

    <para>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><userinput remap="install">touch /etc/ld.so.conf</userinput></screen>

    <para>Install the package:</para>

<screen><userinput remap="install">make install</userinput></screen>

    <para>Install the configuration file and runtime directory for
    <command>nscd</command>:</para>

<screen><userinput remap="install">cp -v ../nscd/nscd.conf /etc/nscd.conf
mkdir -pv /var/cache/nscd</userinput></screen>

    <para revision="systemd">Install the systemd support files for 
    <command>nscd</command>:</para>

    <screen revision="systemd"><userinput remap="install">install -v -Dm644 ../nscd/nscd.tmpfiles /usr/lib/tmpfiles.d/nscd.conf
install -v -Dm644 ../nscd/nscd.service /lib/systemd/system/nscd.service</userinput></screen>

    <para>Next, install the locales that can make the system respond in a
    different language.  None of the locales are required, but if some of them
    are missing, the test suites of future packages would skip important
    testcases.</para>

    <para>Individual locales can be installed using the
    <command>localedef</command> program. E.g., the first
    <command>localedef</command> command below combines the
    <filename>/usr/share/i18n/locales/cs_CZ</filename>
    charset-independent locale definition with the
    <filename>/usr/share/i18n/charmaps/UTF-8.gz</filename>
    charmap definition and appends the result to the
    <filename>/usr/lib/locale/locale-archive</filename> file.
    The following instructions will install the minimum set of
    locales necessary for the optimal coverage of tests:</para>

<screen role="nodump"><userinput remap="locale-test">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 de_DE -f UTF-8 de_DE.UTF-8
localedef -i en_GB -f UTF-8 en_GB.UTF-8
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 en_US -f UTF-8 en_US.UTF-8
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 fr_FR -f UTF-8 fr_FR.UTF-8
localedef -i it_IT -f ISO-8859-1 it_IT
localedef -i it_IT -f UTF-8 it_IT.UTF-8
localedef -i ja_JP -f EUC-JP ja_JP
localedef -i ru_RU -f KOI8-R ru_RU.KOI8-R
localedef -i ru_RU -f UTF-8 ru_RU.UTF-8
localedef -i tr_TR -f UTF-8 tr_TR.UTF-8
localedef -i zh_CN -f GB18030 zh_CN.GB18030</userinput></screen>

    <para>In addition, install the locale for your own country, language and
    character set.</para>

    <para>Alternatively, install all locales listed in the
    <filename>glibc-&glibc-version;/localedata/SUPPORTED</filename> file
    (it includes every locale listed above and many more) at once with the
    following time-consuming command:</para>

<screen><userinput remap="locale-full">make localedata/install-locales</userinput></screen>

    <para>Then use the <command>localedef</command> command to create and
    install locales not listed in the
    <filename>glibc-&glibc-version;/localedata/SUPPORTED</filename> file
    in the unlikely case you need them.</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>

  <sect3>
  <title>Adding nsswitch.conf</title>

    <para>The <filename>/etc/nsswitch.conf</filename> file needs to be created
    because the Glibc defaults do not work well in a networked environment.
    </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>

    </sect3>

    <sect3>
    <title>Adding time zone data</title>

    <para>Install and set up the time zone data with the following:</para>
<screen><userinput>tar -xf ../../tzdata&tzdata-version;.tar.gz

ZONEINFO=/usr/share/zoneinfo
mkdir -pv $ZONEINFO/{posix,right}

for tz in etcetera southamerica northamerica europe africa antarctica  \
          asia australasia backward pacificnew systemv; do
    zic -L /dev/null   -d $ZONEINFO       -y "sh yearistype.sh" ${tz}
    zic -L /dev/null   -d $ZONEINFO/posix -y "sh yearistype.sh" ${tz}
    zic -L leapseconds -d $ZONEINFO/right -y "sh yearistype.sh" ${tz}
done

cp -v zone.tab zone1970.tab iso3166.tab $ZONEINFO
zic -d $ZONEINFO -p America/New_York
unset ZONEINFO</userinput></screen>

    <variablelist>
      <title>The meaning of the zic commands:</title>

      <varlistentry>
        <term><parameter>zic -L /dev/null ...</parameter></term>
        <listitem>
          <para>This creates posix time zones, without any leap seconds.  It is
          conventional to put these in both
          <filename class="directory">zoneinfo</filename> and
          <filename class="directory">zoneinfo/posix</filename>. It is
          necessary to put the POSIX time zones in
          <filename class="directory">zoneinfo</filename>, otherwise various
          test-suites will report errors. On an embedded system, where space is
          tight and you do not intend to ever update the time zones, you could save
          1.9MB by not using the <filename class="directory">posix</filename>
          directory, but some applications or test-suites might produce some
          failures.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><parameter>zic -L leapseconds ...</parameter></term>
        <listitem>
          <para>This creates right time zones, including leap seconds. On an
          embedded system, where space is tight and you do not intend to
          ever update the time zones, or care about the correct time, you could
          save 1.9MB by omitting the <filename class="directory">right</filename>
          directory.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><parameter>zic ... -p ...</parameter></term>
        <listitem>
          <para>This creates the <filename>posixrules</filename> file. We use
          New York because POSIX requires the daylight savings time rules
          to be in accordance with US rules.</para>
        </listitem>
      </varlistentry>
    </variablelist>


    <para>One way to determine the local time zone is to 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>America/Edmonton</emphasis>). There are also some other possible
    time zones listed in <filename
    class='directory'>/usr/share/zoneinfo</filename> such as
    <emphasis>Canada/Eastern</emphasis> or <emphasis>EST5EDT</emphasis> that
    are not identified by the script but can be used.</para>

    <para>Then create the <filename>/etc/localtime</filename> file by
    running:</para>

<screen revision="sysv"><userinput>cp -v /usr/share/zoneinfo/<replaceable>&lt;xxx&gt;</replaceable> /etc/localtime</userinput></screen>

<screen revision="systemd"><userinput>ln -sfv /usr/share/zoneinfo/<replaceable>&lt;xxx&gt;</replaceable> /etc/localtime</userinput></screen>

    <para>Replace <replaceable>&lt;xxx&gt;</replaceable> with the name of the
    time zone selected (e.g., Canada/Eastern).</para>

  </sect3>

  <sect3 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
</literal>
EOF</userinput></screen>

  <para>If desired, the dynamic loader can also search a directory and
  include the contents of files found there.  Generally the files in
  this include directory are one line specifying the desired library path.
  To add this capability run the following commands:</para>

<screen role="nodump"><userinput>cat &gt;&gt; /etc/ld.so.conf &lt;&lt; "EOF"
<literal># Add an include directory
include /etc/ld.so.conf.d/*.conf
</literal>
EOF
mkdir -pv /etc/ld.so.conf.d</userinput></screen>

  </sect3>
  </sect2>

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

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

      <seglistitem>
        <seg>catchsegv, gencat, getconf, getent, iconv, iconvconfig, ldconfig,
        ldd, lddlibc4, locale, localedef, makedb, mtrace, nscd, 
        pldd, rpcgen, sln, sotruss, sprof, tzselect, xtrace,
        zdump, and zic</seg>
        <seg>ld-&glibc-version;.so, libBrokenLocale.{a,so}, libSegFault.so, libanl.{a,so},
        libc.{a,so}, libc_nonshared.a, libcidn.so,
        libcrypt.{a,so}, libdl.{a,so}, libg.a, libieee.a, libm.{a,so},
        libmcheck.a, libmemusage.so, libnsl.{a,so}, libnss_compat.so,
        libnss_dns.so, libnss_files.so, libnss_hesiod.so, libnss_nis.so,
        libnss_nisplus.so, libpthread.{a,so},
        libpthread_nonshared.a, libresolv.{a,so}, librpcsvc.a, librt.{a,so},
        libthread_db.so, and libutil.{a,so}</seg>
        <seg>/usr/include/arpa, /usr/include/bits, /usr/include/gnu,
        /usr/include/net, /usr/include/netash, /usr/include/netatalk,
        /usr/include/netax25, /usr/include/neteconet, /usr/include/netinet,
        /usr/include/netipx, /usr/include/netiucv, /usr/include/netpacket,
        /usr/include/netrom, /usr/include/netrose, /usr/include/nfs,
        /usr/include/protocols, /usr/include/rpc, /usr/include/rpcsvc,
        /usr/include/sys, /usr/lib/audit, /usr/lib/gconv, /usr/lib/locale,
        /usr/libexec/getconf, /usr/share/i18n, /usr/share/zoneinfo,
        /var/cache/nscd, and /var/lib/nss_db</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>Prints various information about the current locale</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="makedb">
        <term><command>makedb</command></term>
        <listitem>
          <para>Creates a simple database from textual input</para>
          <indexterm zone="ch-system-glibc makedb">
            <primary sortas="b-makedb">makedb</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="pldd">
        <term><command>pldd</command></term>
        <listitem>
          <para>Lists dynamic shared objects used by running processes</para>
          <indexterm zone="ch-system-glibc pldd">
            <primary sortas="b-pldd">pldd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

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

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

      <varlistentry id="sotruss">
        <term><command>sotruss</command></term>
        <listitem>
          <para>Traces shared library procedure calls of a specified command</para>
          <indexterm zone="ch-system-glibc sotruss">
            <primary sortas="b-sotruss">sotruss</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-&glibc-version;.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-&glibc-version;.so</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libBrokenLocale">
        <term><filename class="libraryfile">libBrokenLocale</filename></term>
        <listitem>
          <para>Used internally by Glibc as a gross hack to get broken programs
          (e.g., some Motif applications) running. See comments in
          <filename>glibc-&glibc-version;/locale/broken_cur_max.c</filename>
          for more information</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, used by
          <command>catchsegv</command></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="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="libcidn">
        <term><filename class="libraryfile">libcidn</filename></term>
        <listitem>
          <para>Used internally by Glibc for handling internationalized domain
          names in the <function>getaddrinfo()</function> function</para>
          <indexterm zone="ch-system-glibc libcidn">
            <primary sortas="c-libcidn">libcidn</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>Dummy library containing no functions. Previously was 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>Linking in this module forces error handling rules for math
          functions as defined by the Institute of Electrical and Electronic
          Engineers (IEEE). The default is POSIX.1 error handling</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>Turns on memory allocation checking when linked to</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> 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="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>