1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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5 | %general-entities;
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6 | ]>
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7 |
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8 | <sect1 arch="ml_32,ml_x32,ml_all" id="pre-multilib">
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9 | <?dbhtml filename="multilib.html"?>
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10 |
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11 | <title>About the Multilib Edition</title>
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12 |
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13 | <sect2><title>What is Multilib</title>
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14 |
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15 | <para>Today, most systems in the x86 world have a word size of 64
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16 | bit. The word size is a number of bits which can be used at once
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17 | in the most efficient way. Previous architectures of x86 processors
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18 | had a word size of 32 bit which means they have a different
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19 | understanding of what is the best alignment of data in memory as
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20 | well as they have a different mechanism to address a different size
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21 | of memory. Even the instruction set of the 64 bit processors is
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22 | quite simmilar to the instructions of 32 bit processors, binaries
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23 | (objects compiled to machine code) cannot directly be executed on
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24 | 64 bit systems.</para>
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25 |
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26 | <para>Multilib is a mechanism to provide support for the 32 bit
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27 | binaries so that they can be executed of modern 64 bit CPUs.</para>
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28 |
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29 | </sect2>
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30 |
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31 | <sect2><title>Why doing Multilib?</title>
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32 |
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33 | <para>From a educational point of view, LFS in its 'native' form is
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34 | probably the best way to see how a Linux system is built from source.
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35 | There is no need to confuse with different architectures. But when
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36 | there is a need to run 32 binaries and you don't want to build the
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37 | whole system in 32 bit (which would be waste of ressources
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38 | nowadays) than LFS-multilib is an option. Examples for such a
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39 | need could be
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40 | <itemizedlist>
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41 | <listitem><para>Closed-source software without source only
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42 | available for 32 bit. That may be the case for printer driver
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43 | or any other kind of hardware drivers, the company provides
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44 | the binaries. If you have such a driver, LFS-multilib
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45 | may help you getting the stuff running</para>
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46 | </listitem>
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47 | <listitem><para>If you want to go far beyond LFS and setup a
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48 | virtualization platform like <application>VirtualBox</application>,
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49 | you will need multilib support</para>
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50 | </listitem>
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51 | <listitem><para>or even just because you can</para>
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52 | </listitem>
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53 | </itemizedlist>
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54 |
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55 | </para>
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56 |
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57 | <para>The multilib edition of LFS goes a small step beyond and a
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58 | small step back to what has been said in the previous section
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59 | when talking about target architectures. On one hand, the multilib
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60 | edition is focused and <emphasis>limited</emphasis> to x86_64
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61 | architectures only, on the other hand, it <emphasis>expands</emphasis>
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62 | the instructions to utilize both possible architectures, namely
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63 | 32-bit as well as 64-bit.</para>
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64 |
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65 | <para>It also goes a bit beyond the basic educational
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66 | approach of LFS which is to show you how to build a Linux system.
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67 | To achieve this, no support for additional architectures than
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68 | the default one for your system is required. If you haven't
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69 | previously built by the standard LFS book, you are encouraged to
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70 | do so before using this edition.</para>
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71 |
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72 | </sect2>
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73 |
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74 | <sect2><title>Building a Multilib System</title>
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75 |
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76 | <para>Building a multilib system is not that much different from
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77 | building a system by using the 'native' LFS book. Beside some
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78 | tweaks here and there the most prominent difference is that
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79 | multilib requires compiling some applications up to three times:
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80 | one for the primary 64-bit architecture,
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81 | one for the 32-bit architecture (m32),
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82 | and once again for the 32-bit architecture with is 32-bit memory
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83 | access and 64 bit instruction set (mx32).</para>
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84 |
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85 | <para>Continue only if you and your system meets the following
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86 | requirements:
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87 | <itemizedlist>
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88 | <listitem><para>you have a x86_64 compatible machine</para></listitem>
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89 | <listitem><para>you already have some experience with LFS</para></listitem>
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90 | <listitem><para>you have a need for 32-bit support</para></listitem>
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91 | </itemizedlist>
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92 | </para>
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93 |
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94 | <para>If you passed all three requirements, go ahead and build LFS
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95 | in multilib mode.</para>
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96 |
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97 | </sect2>
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98 |
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99 | </sect1>
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