source: chapter06/glibc.xml@ 1dc34de7

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<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 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 then give false results and defeat the 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 \
    --with-__thread --enable-kernel=2.6.0 --without-cvs \
    --libexecdir=/usr/lib/glibc \
    --with-headers=/tools/glibc-kernheaders</userinput></screen>

<para>The meaning of the new configure option:</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 check</userinput></screen>

<para>The Glibc test suite is highly dependent on certain functions of
the 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. This is a list of the most common
issues:</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. This sometimes occurs because
of other file system quirks as well.</para></listitem>

<listitem><para>The <emphasis>shm</emphasis> test can fail when the
host system is using the <systemitem
class="filesystem">devfs</systemitem> file system but does not have
the <systemitem class="filesystem">tmpfs</systemitem> file system
mounted at <filename class="directory">/dev/shm</filename>.  This
occurs because of a lack of support for tmpfs in the
kernel.</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>

<para>To save yourself a lot of time, an alternative to running the
previous command (which generates and installs every locale Glibc is
aware of) 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 <emphasis>install-locales</emphasis>
target used 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>Some locales installed by the <command>make
localedata/install-locales</command> command above are not properly
supported by some applications that are in the LFS and BLFS books.
Because of the various problems that arise due to application
programmers making assumptions that break in such locales, LFS 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 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 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>

<para>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>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>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 with
networking. The time zone also 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>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 --remove-destination /usr/share/zoneinfo/<replaceable>[xxx]</replaceable> /etc/localtime</userinput></screen>

<para>Replace [xxx] with the name of the time zone that the
<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 them 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"
# 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 files.</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>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>a program that reads and interprets a memory trace file and
ouputs a summary in human-readable format.</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>a daemon that provides 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 <command>grantpt</command> 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 Remote Procecure call (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>a statically linked <command>ln</command> program.</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>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>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>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>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>the segmentation fault signal handler.</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>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>the main C library.</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>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>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>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>the Institute of Electrical and Electronic Engineers (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>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>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>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>the Name Service Switch libraries,
containing functions for resolving host names, user names, group names,
aliases, services, protocols, etc.</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>