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+<?xml version="1.0" encoding="ISO-8859-1"?>
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+<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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+ <!ENTITY % general-entities SYSTEM "../general.ent">
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+ %general-entities;
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+]>
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+
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+<sect1 arch="multilib" id="pre-multilib">
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+ <?dbhtml filename="multilib.html"?>
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+
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+ <title>About the Multilib Edition</title>
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+
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+ <sect2><title>What is 'multilib'</title>
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+
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+ <para>Today, most systems in the x86 world have a word size of 64
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+ bit. The word size is a number of bits which can be used at once
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+ in the most efficient way. Previous architectures of x86 processors
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+ had a word size of 32 bit which means they have a different
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+ understanding of what is the best alignment of data in memory as
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+ well as they have a different mechanism to address a different size
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+ of memory. Even the instruction set of the 64 bit processors is
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+ quite simmilar to the instructions of 32 bit processors, binaries
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+ (objects compiled to machine code) cannot directly be executed on
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+ 64 bit systems.</para>
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+
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+ <para>Multilib is a mechanism to provide support for the 32 bit
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+ binaries so that they can be executed of modern 64 bit CPUs.</para>
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+
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+ </sect2>
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+
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+ <sect2><title>Why doing multilib?</title>
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+
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+ <para>From a educational point of view, LFS in its 'native' form is
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+ probably the best way to see how a Linux system is built from source.
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+ There is no need to confuse with different architectures. But when
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+ there is a need to run 32 binaries and you don't want to build the
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+ whole system in 32 bit (which would be waste of ressources
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+ nowadays) than LFS-multilib is an option. Examples for such a
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+ need could be
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+ <itemizedlist>
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+ <listitem><para>Closed-source software without source only
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+ available for 32 bit. That may be the case for printer driver
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+ or any other kind of hardware drivers, the company provides
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+ the binaries. If you have such a driver, LFS-multilib
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+ may help you getting the stuff running</para>
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+ </listitem>
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+ <listitem><para>If you want to go far beyond LFS and setup a
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+ virtualization platform like <application>VirtualBox</application>,
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+ you will need multilib support</para>
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+ </listitem>
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+ <listitem><para>or even just because you can</para>
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+ </listitem>
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+ </itemizedlist>
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+
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+ </para>
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+
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+ <para>This multilib edition of LFS goes a small step beyond and a
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+ small step back to what has been said in the previous section
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+ when talking about target architectures. On one hand, the multilib
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+ edition is focused and <emphasis>limited</emphasis> to x86_64
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+ architectures only, on the other hand, it <emphasis>expands</emphasis>
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+ the instructions to utilize both possible architectures, namely
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+ 32-bit as well as 64-bit.</para>
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+
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+ <para>It also goes a bit beyond the basic educational
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+ approach of LFS which is to show you how to build a Linux system.
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+ To achieve this, no support for additional architectures than
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+ the default one for your system is required. If you haven't
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+ previously built by the standard LFS book, you are encouraged to
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+ do so before using this edition.</para>
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+
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+ </sect2>
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+
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+ <sect2><title>Building a multilib system</title>
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+
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+ <para>Building a multilib system is not that much different from
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+ building a system by using the 'native' LFS book. Beside some
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+ tweaks here and there the most prominent difference is that
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+ multilib requires compiling many applications three times:
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+ one for the primary 64-bit architecture,
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+ one for the minor 32-bit architecture (m32),
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+ and once again for the 32-bit architecture with 64-bit memory
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+ extensions (mx32).</para>
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+
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+ <para>Continue only if you and your system meets the following
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+ requirements:
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+ <itemizedlist>
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+ <listitem><para>you have a x86_64 compatible machine</para></listitem>
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+ <listitem><para>you already have some experience with LFS</para></listitem>
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+ <listitem><para>you have a need for 32-bit support</para></listitem>
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+ </itemizedlist>
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+ </para>
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+
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+ <para>If you passed all three requirements, go ahead and build LFS
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+ in multilib mode.</para>
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+
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+ </sect2>
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+
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+</sect1>
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Thomas Trepl