lfs-book/chapter06/glibc.xml

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<sect1 id="ch-system-glibc" role="wrap">
<title>Glibc-&glibc-version;</title>
<?dbhtml filename="glibc.html"?>

<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>16.7 SBU</seg><seg>500 MB</seg></seglistitem>
</segmentedlist>

<segmentedlist>
<segtitle>&dependencies;</segtitle>
<seglistitem><seg>Bash, Binutils, Coreutils, Diffutils,
Gawk, GCC, Gettext, Grep, Make, Perl, Sed, and Texinfo</seg></seglistitem>
</segmentedlist>
</sect2>

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

<note><para>Some packages outside of LFS 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 an LFS
system.</para></note>

<para>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>The glibc-libidn tarball adds support for internationalized
domain names (IDN) to Glibc. Note that many programs that
support IDN require the full libidn library from
<ulink url="http://josefsson.org/libidn/releases/"/>, not this add-on.
Unpack the tarball from within the Glibc source
directory:</para>

<screen><userinput>tar jxf ../glibc-libidn-&glibc-version;.tar.bz2</userinput></screen>

<para>In the vi_VN.TCVN locale, bash enters infinite loop at startup. It is
unknown whether this is a bash bug or a glibc problem. Disable installation
of this locale in order to avoid the problem:</para>

<screen><userinput>sed -i '/vi_VN.TCVN/d' localedata/SUPPORTED</userinput></screen>

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

<screen><userinput>mkdir -v ../glibc-build
cd ../glibc-build</userinput></screen>

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

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

<para>The meaning of the new configure options:</para>

<variablelist>
<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>Compile the package:</para>

<screen><userinput>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>Test the results:</para>

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

<para>On at least i686 you can expect to see failures in the <emphasis>test-double
</emphasis> and <emphasis>test-idouble</emphasis> math tests with
gcc-&gcc-version;, as well as an expected (ignored) failure in <emphasis>
posix/annexc</emphasis>.  These two failures in the math tests appear to be
harmless.</para>

<para>The Glibc test suite is highly dependent on certain functions of
the host system, in particular the kernel. In certain circumstances,
some failures are unavoidable. This is a list of the most common
issues:</para>

<itemizedlist>
<listitem><para>The <emphasis>math</emphasis> tests sometimes fail in other tests
when running
on systems where the CPU is not a relatively new genuine Intel or authentic AMD.
Certain optimization settings are also known to be a factor here.</para></listitem>

<listitem><para>The <emphasis>gettext</emphasis> test sometimes fails due to
host system issues. The exact reasons are not yet clear.</para></listitem>

<listitem><para>If you have mounted the LFS partition with the
<parameter>noatime</parameter> option, the <emphasis>atime</emphasis> test will
fail. As mentioned in <xref linkend="space-mounting"/>, do not use the
<parameter>noatime</parameter> option while building LFS.</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>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>touch /etc/ld.so.conf</userinput></screen>

<para>Install the package:</para>

<screen><userinput>make install</userinput></screen>

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

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

<note><para>It is possible to create and install additional locales such as
ru_RU.CP1251 by means of the <command>localedef</command> command, as
explained in the <filename>INSTALL</filename> file in the Glibc source.</para></note>
<!-- The Live CD patches the localedata/SUPPORTED file instead of running localedef -->

<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>

<!-- FIXME: recheck that "make localedata/install_locales" actually does the same -->
<screen role="nodump"><userinput>mkdir -pv /usr/lib/locale
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 fr_FR.UTF-8 -f UTF-8 fr_FR
localedef -i it_IT -f ISO-8859-1 it_IT
localedef -i ja_JP -f EUC-JP ja_JP</userinput></screen>

<para>The first <command>localedef</command> above combines the
<filename>/usr/share/i18n/locales/de_DE</filename> charset-independent
locale definition with the
<filename>/usr/share/i18n/charmaps/ISO-8859-1.gz</filename> charmap definition
and appends the result to the
<filename>/usr/lib/locale/locale-archive</filename> file.</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>

<para>The meaning of the cp option:</para>

<variablelist>
<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 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, nscd_nischeck, 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="nscd_nischeck">
<term><command>nscd_nischeck</command></term>
<listitem>
<para>Checks whether or not secure mode is necessary for NIS+ lookup</para>
<indexterm zone="ch-system-glibc nscd_nischeck"><primary sortas="b-nscd_nischeck">nscd_nischeck</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 <command>ln</command> program</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> 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>