lfs-book/chapter06/glibc-exp.xml

<sect2>
<title>Command explanations</title>

<para><userinput>mknod -m 0666 /dev/null c 1 3:</userinput> Glibc needs a
null device to compile properly. All other devices will be created in the
next section.</para>

<para><userinput>touch /etc/ld.so.conf</userinput> One of the final steps 
of the Glibc installation is running ldconfig to update the dynamic loader 
cache.  If this file doesn't exist, the installation will abort with an error 
that it can't read the file, so we simply create an empty file (the empty file 
will have Glibc default to using /lib and /usr/lib which is fine).</para>

<para><userinput>sed 's%\$(PERL)%/usr/bin/perl%' 
malloc/Makefile.backup &gt; malloc/Makefile:</userinput> This sed command
searches through <filename>malloc/Makefile.backup</filename> and
converts all occurrences of <filename>$(PERL)</filename> to
<filename>/usr/bin/perl</filename>. The output is then written to the
original <filename>malloc/Makefile.in</filename> which is used during
configuration. This is done because Glibc can't autodetect perl since
it hasn't been installed yet.</para>

<para><userinput>sed 's/root/0' login/Makefile.backup &gt;
login/Makefile:</userinput> This sed command replaces all occurences of
<filename>root</filename> in <filename>login/Makefile.backup</filename>
with 0. This is because we don't have glibc on the LFS system yet, so
usernames can't be resolved to their user id's. Therefore, we replace
the username root with user id 0.</para>

<para><userinput>--enable-add-ons:</userinput> This enables the add-on that
we install with Glibc: linuxthreads</para>

<para><userinput>--libexecdir=/usr/bin:</userinput> This will cause the
pt_chown program to be installed in the /usr/bin directory.</para>

<para><userinput>sed 's/cross-compiling = yes/cross-compiling = no/'
config.make.backup &gt; config.make:</userinput> This time, sed searches
through <filename>config.make.backup</filename> and replaces all occurences
of <filename>cross-compiling = yes</filename> with
<filename>cross-compiling = no</filename>. We do this because we are
only building for our own system. Cross-compiling is used, for instance,
to build a package for an Apple Power PC on an Intel system. The reason
Glibc thinks we're cross-compiling is that it can't compile a test program
to determine this, so it automatically defaults to a cross-compiler.
Compiling the test program failes because Glibc hasn't been installed
yet.</para>

<para><userinput>exec /bin/bash:</userinput>This command will
start a new bash shell which will replace the current shell. This is 
done to get rid of the "I have no name!" message in the command 
prompt, which was caused by bash's inability to resolve a userid to 
a username (which in turn was caused by the missing Glibc 
installation).</para>

</sect2>