source: chapter06/glibc.xml@ e4bf4c7

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

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

<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>

<screen>&buildtime; 12.3 SBU
&diskspace; 784 MB</screen>

<para>Glibc installation depends on: Bash, Binutils, Coreutils, Diffutils,
Gawk, GCC, Gettext, Grep, Make, Perl, Sed, Texinfo.</para>



<sect2>
<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>/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>

<itemizedlist>
<listitem><para><userinput>--libexecdir=/tmp/pt_chown</userinput>: This changes
the location of the <filename>pt_chown</filename> 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>
</itemizedlist>

<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 test suite notes from <xref linkend="ch-tools-glibc"/> are still very much
appropriate here. Be sure to refer back there should you have any doubts.</para>

<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"><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"</userinput>
# 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
<userinput>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>

<itemizedlist>
<listitem><para><userinput>--remove-destination</userinput>: 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>/usr</filename> is
on a separate partition. This could matter, for example, when booted into single
user mode.</para></listitem>
</itemizedlist>

<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">
<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>/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"</userinput>
# Begin /etc/ld.so.conf

/usr/local/lib
/opt/lib

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

</sect2>


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

<para><emphasis>Installed programs</emphasis>: 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</para>

<para><emphasis>Installed libraries</emphasis>: 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]</para>

</sect2>


<sect2><title>Short descriptions</title>

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

<indexterm zone="ch-system-glibc sln"><primary sortas="b-sln">sln</primary></indexterm>
<para id="sln"><command>sln</command> 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>

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

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

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

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

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

<indexterm zone="ch-system-glibc ld.so"><primary sortas="c-ld.so">ld.so</primary></indexterm>
<para id="ld.so"><command>ld.so</command> is the helper program for shared library
executables.</para>

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

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

<indexterm zone="ch-system-glibc libanl"><primary sortas="c-libanl">libanl</primary></indexterm>
<para id="libanl"><command>libanl</command> is an asynchronous name lookup
library.</para>

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

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

<indexterm zone="ch-system-glibc libcrypt"><primary sortas="c-libcrypt">libcrypt</primary></indexterm>
<para id="libcrypt"><command>libcrypt</command> is the cryptography library.</para>

<indexterm zone="ch-system-glibc libdl"><primary sortas="c-libdl">libdl</primary></indexterm>
<para id="libdl"><command>libdl</command> is the dynamic linking interface library.</para>

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

<indexterm zone="ch-system-glibc libieee"><primary sortas="c-libieee">libieee</primary></indexterm>
<para id="libieee"><command>libieee</command> is the IEEE floating point library.</para>

<indexterm zone="ch-system-glibc libm"><primary sortas="c-libm">libm</primary></indexterm>
<para id="libm"><command>libm</command> is the mathematical library.</para>

<indexterm zone="ch-system-glibc libmcheck"><primary sortas="c-libmcheck">libmcheck</primary></indexterm>
<para id="libmcheck"><command>libmcheck</command> contains code run at boot.</para>

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

<indexterm zone="ch-system-glibc libnsl"><primary sortas="c-libnsl">libnsl</primary></indexterm>
<para id="libnsl"><command>libnsl</command> is the network services library.</para>

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

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

<indexterm zone="ch-system-glibc libpthread"><primary sortas="c-libpthread">libpthread</primary></indexterm>
<para id="libpthread"><command>libpthread</command> is the POSIX threads library.</para>

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

<indexterm zone="ch-system-glibc librpcsvc"><primary sortas="c-librpcsvc">librpcsvc</primary></indexterm>
<para id="librpcsvc"><command>librpcsvc</command>contains functions providing
miscellaneous RPC services.</para>

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

<indexterm zone="ch-system-glibc libthread_db"><primary sortas="c-libthread_db">libthread_db</primary></indexterm>
<para id="libthread_db"><command>libthread_db</command> contains functions useful for
building debuggers for multi-threaded programs.</para>

<indexterm zone="ch-system-glibc libutil"><primary sortas="c-libutil">libutil</primary></indexterm>
<para id="libutil"><command>libutil</command> contains code for "standard" functions
used in many different Unix utilities.</para>

</sect2>



</sect1>