Added the missing command explanations

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@755 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter06/glibc-exp.xml

@@ -15,10 +15,63 @@ can't read the file. So we create an empty file for it (the empty file
 will have Glibc default to using /lib and /usr/lib which is fine right now).
 </para>
 
+<para>
+<userinput>sed s/"\$(PERL)"/"\/usr\/bin\/perl"/
+../glibc-2.2.3/malloc/Makefile &gt; tmp~:</userinput> This sed command
+searches through <filename>../glibc-2.2.3/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~ ../glibc-2.2.3/malloc/Makefile:</userinput> The file
+<filename>tmp~</filename> is now moved back to
+<filename>../glibc-2.2.3/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" ../glibc-2.2.3/login/Makefile &gt;
+tmp~:</userinput> This sed command replaces all occurances of
+<filename>root</filename> in
+<filename>../glibc-2.2.3/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~ ../glibc-2.2.3/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 determin this, so it automatically default 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>
+
 </sect2>