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 &gt; tmp~:</userinput> This sed command
searches through <filename>malloc/Makefile</filename> and
converts all occurances of <filename>$(PERL)</filename> to
<filename>/usr/bin/perl</filename>.  The output is then written to the
file <filename>tmp~</filename>.  This is done because Glibc can't
autodetect perl since it's not installed yet at the time when we install
Glibc.</para>

<para><userinput>mv tmp~ malloc/Makefile:</userinput> The file
<filename>tmp~</filename> is now moved back to
<filename>malloc/Makefile</filename>.  We do this because
when using sed, we can't write straight back to this file so we need to
use a temporary file in between.</para>

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

<para><userinput>mv tmp~ login/Makefile:</userinput> As above, we are using 
a temporary file (<filename>tmp~</filename>) to store the
edited Makefile and then copying it back over the original.</para>

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

<para><userinput>sed 's/cross-compiling = yes/cross-compiling = no/'
config.make &gt; config.make~:</userinput> This time, we're replacing
<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. The reason for the failed program is because Glibc
hasn't been installed yet.</para>

<para><userinput>mv config.make~ config.make:</userinput> Again, we are moving
the temporary file over the original.</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>