source: chapter06/glibc.xml@ 84988c0

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>
<sect1 id="ch-system-glibc" xreflabel="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 all
the basic routines for allocating memory, searching directories, opening and
closing files, reading and writing them, string handling, pattern matching,
arithmetic, and so on.</para>

<segmentedlist>
<segtitle>&buildtime;</segtitle>
<segtitle>&diskspace;</segtitle>
<seglistitem><seg>12.3 SBU</seg><seg>784 MB</seg></seglistitem>
</segmentedlist>

<segmentedlist>
<segtitle>Glibc installation depends on</segtitle>
<seglistitem><seg>Bash, Binutils, Coreutils, Diffutils,
Gawk, GCC, Gettext, Grep, Make, Perl, Sed, Texinfo</seg></seglistitem>
</segmentedlist>
</sect2>

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

<para>The Glibc build system is very well self-contained and will install
perfectly, even though our compiler specs file and linker are still pointing
at <filename class="directory">/tools</filename>. We cannot adjust the specs and linker before
the Glibc install, because the Glibc autoconf tests would then give bogus
results and thus defeat our goal of achieving a clean build.</para>

<para>Before starting to build Glibc, remember to unset any environment
variables that override the default optimization flags.</para>

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

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

<para>Now prepare Glibc for compilation:</para>

<screen><userinput>../glibc-&glibc-version;/configure --prefix=/usr \
    --disable-profile --enable-add-ons=nptl --with-tls \
    --libexecdir=/tmp/pt_chown --without-cvs \
    --with-headers=/tools/glibc-kernheaders</userinput></screen>

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

<variablelist>
<varlistentry>
<term><parameter>--libexecdir=/tmp/pt_chown</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">/tmp/pt_chown</filename>. This program isn't required
on modern systems, so we install it in a place from which we will delete it
later.</para></listitem>
</varlistentry>
</variablelist>

<para>Compile the package:</para>

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

<important><para>The test suite for Glibc in this section is considered
<emphasis>critical</emphasis>. Our advice is to not skip it under any
circumstance.</para></important>

<para>Test the results:</para>

<screen><userinput>make check</userinput></screen>

<para>The Glibc test suite is highly dependent on certain functions of your host
system, in particular the kernel.  In general, the Glibc test suite is always
expected to pass. However, in certain circumstances some failures are
unavoidable. Here is a list of the most common issues we are aware of:</para>

<itemizedlist>
<listitem><para>The <emphasis>math</emphasis> tests sometimes fail 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>The <emphasis>atime</emphasis> test sometimes fails when the
LFS partition is mounted with the <parameter>noatime</parameter> option, or due
to other file system quirks.</para></listitem>

<listitem><para>The <emphasis>shm</emphasis> test might fail when the host
system is running the devfs file system but doesn't have the <systemitem class="filesystem">tmpfs</systemitem> file system
mounted at <filename class="directory">/dev/shm</filename> due to lack of support for tmpfs in
the kernel.</para></listitem>

<listitem><para>When running on older and slower hardware, some tests might
fail due to 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>. Fix this
annoying little warning with:</para>

<screen><userinput>touch /etc/ld.so.conf</userinput></screen>

<para>And install the package:</para>

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

<para>The locales that can make your system respond in a different language
weren't installed by the above command. Do it with this:</para>

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

<para>An alternative to running the previous command is to install only those
locales which you need or want. This can be achieved by using the
<command>localedef</command> command. Information on this can be found in
the <filename>INSTALL</filename> file in the Glibc source. However, there are
a number of locales that are essential for the tests of future packages to
pass, in particular, the <emphasis>libstdc++</emphasis> tests from GCC. The
following instructions, instead of the install-locales target above, will
install the minimum set of locales necessary for the tests to run
successfully:</para>

<screen><userinput>mkdir -p /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 it_IT -f ISO-8859-1 it_IT
localedef -i ja_JP -f EUC-JP ja_JP</userinput></screen>

<para>In fact, some locales installed by the
<command>make localedata/install-locales</command>
command above are not properly
supported by some applications that are in LFS and BLFS books. Because
of various problems that arise
due to application programmers making
assumptions that break in such locales, LFS <emphasis>should not</emphasis>
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 not to support such complex locales.
This applies to the ja_JP and fa_IR locales as well:
they have been installed only
for GCC and Gettext tests to pass, and e.g.
the <command>watch</command> program (part of Procps)
compiled according to this book doesn't work properly in them.
Various attempts to circumvent these
restrictions are documented in internationalization-related hints.</para>

<para>Finally, build the linuxthreads man pages, which are a great reference
on the threading API (applicable to NPTL as well):</para>

<screen><userinput>make -C ../glibc-&glibc-version;/linuxthreads/man</userinput></screen>

<para>And install these pages:</para>

<screen><userinput>make -C ../glibc-&glibc-version;/linuxthreads/man install</userinput></screen>

</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>We need to create the <filename>/etc/nsswitch.conf</filename> file,
because, although Glibc provides defaults when this file is missing or corrupt,
the Glibc defaults don't work well with networking. Also, our time zone needs
to be set up.</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"
# 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
EOF</userinput></screen>

<para>To find out what time zone you're in, run the following script:</para>

<screen><userinput>tzselect</userinput></screen>

<para>When you've answered a few questions about your location, the script will
output the name of your time zone, something like <emphasis>EST5EDT</emphasis>
or <emphasis>Canada/Eastern</emphasis>. Then create the
<filename>/etc/localtime</filename> file by running:</para>

<screen><userinput>cp --remove-destination /usr/share/zoneinfo/Canada/Eastern /etc/localtime</userinput></screen>

<para>The meaning of the 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 why we copy instead of symlink is to cover the situation where 
<filename class="directory">/usr</filename> is on a separate partition. This could matter, for
example, when booted into single user mode.</para></listitem>
</varlistentry>
</variablelist>

<para>Of course, instead of <emphasis>Canada/Eastern</emphasis>, fill in
the name of the time zone that the <command>tzselect</command> script
gave you.</para>

</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 when you run them. However, if there are libraries in
directories other than <filename class="directory">/lib</filename> and
<filename class="directory">/usr/lib</filename>, you need to add them to
the <filename>/etc/ld.so.conf</filename> file 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 we 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"
# Begin /etc/ld.so.conf

/usr/local/lib
/opt/lib

# End /etc/ld.so.conf
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, glibcbug, 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], libc_nonshared.a,
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><title>Short descriptions</title>

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

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

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

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

<varlistentry id="glibcbug">
<term><command>glibcbug</command></term>
<listitem>
<indexterm zone="ch-system-glibc glibcbug"><primary sortas="b-glibcbug">glibcbug</primary></indexterm>
<para>creates a bug report and mails it to the bug email address.</para>
</listitem>
</varlistentry>

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

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

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

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

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

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

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

<varlistentry id="mtrace">
<term><command>mtrace</command></term>
<listitem>
<indexterm zone="ch-system-glibc mtrace"><primary sortas="b-mtrace">mtrace</primary></indexterm>
<para>...</para>
</listitem>
</varlistentry>

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

<varlistentry id="nscd_nischeck">
<term><command>nscd_nischeck</command></term>
<listitem>
<indexterm zone="ch-system-glibc nscd_nischeck"><primary sortas="b-nscd_nischeck">nscd_nischeck</primary></indexterm>
<para>checks whether or not secure mode is necessary for NIS+ lookup.</para>
</listitem>
</varlistentry>

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

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

<varlistentry id="rpcgen">
<term><command>rpcgen</command></term>
<listitem>
<indexterm zone="ch-system-glibc rpcgen"><primary sortas="b-rpcgen">rpcgen</primary></indexterm>
<para>generates C code to implement the RPC protocol.</para>
</listitem>
</varlistentry>

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

<varlistentry id="sln">
<term><command>sln</command></term>
<listitem>
<indexterm zone="ch-system-glibc sln"><primary sortas="b-sln">sln</primary></indexterm>
<para>is used to make symbolic links. The program
is statically linked, so it is useful for making symbolic links to dynamic
libraries if the dynamic linking system for some reason is nonfunctional.</para>
</listitem>
</varlistentry>

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

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

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

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

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

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

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

<varlistentry id="libSegFault">
<term><filename class="libraryfile">libSegFault</filename></term>
<listitem>
<indexterm zone="ch-system-glibc libSegFault"><primary sortas="c-libSegFault">libSegFault</primary></indexterm>
<para>is a segmentation fault signal handler. It tries to catch segfaults.</para>
</listitem>
</varlistentry>

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

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

<varlistentry id="libc">
<term><filename class="libraryfile">libc</filename></term>
<listitem>
<indexterm zone="ch-system-glibc libc"><primary sortas="c-libc">libc</primary></indexterm>
<para>is the main C library -- a collection of commonly used functions.</para>
</listitem>
</varlistentry>

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

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

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

<varlistentry id="libieee">
<term><filename class="libraryfile">libieee</filename></term>
<listitem>
<indexterm zone="ch-system-glibc libieee"><primary sortas="c-libieee">libieee</primary></indexterm>
<para>is the IEEE floating point library.</para>
</listitem>
</varlistentry>

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

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

<varlistentry id="libmemusage">
<term><filename class="libraryfile">libmemusage</filename></term>
<listitem>
<indexterm zone="ch-system-glibc libmemusage"><primary sortas="c-libmemusage">libmemusage</primary></indexterm>
<para>is used by <command>memusage</command> to help collect
information about the memory usage of a program.</para>
</listitem>
</varlistentry>

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

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

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

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

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

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

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

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

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

</sect2>

</sect1>