[fa7acfc] | 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 id="pre-cross">
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| 9 | <?dbhtml filename="cross.html"?>
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| 10 |
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| 11 | <title>About the Cross Edition</title>
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| 12 |
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| 13 | <para>While LFS has provided an approach to build a Linux system entirely
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| 14 | from source code, it builds the LFS system in a
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| 15 | <emphasis>chroot</emphasis> environment. The chroot environment is almost
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| 16 | seperate from the host distribution, but it still relies on the hardware
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| 17 | and Linux kernel from the host system.</para>
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| 18 |
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| 19 | <para>The Cross Edition contains modification to the LFS book, allowing
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| 20 | to boot the temporary system instead of chroot. So it's possible to
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| 21 | bootstrap a Linux system for a target where no Linux distribution exists.
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| 22 | And, the kernel ABI may frequently change at the early stage porting Linux
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| 23 | to a new hardware. The modification in this edition completely removes
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| 24 | the dependency on the kernel from the host distribution, allowing to
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| 25 | rebuild the entire system with a new kernel ABI.</para>
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| 26 |
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| 27 | <para>If you already have a Linux distribution running on the hardware
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| 28 | where you need a Linux From Scratch system, with the kernel ABI you want,
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| 29 | and it's compatible with the Host System Requirements specified by the
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| 30 | LFS book, it's likely you should read the original LFS book instead of
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| 31 | this edition.</para>
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| 32 |
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| 33 | <para>This edition contains instructions to bootstrap a Linux system for
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[0400cfe] | 34 | x86 (32-bit or 64-bit). It may look irrational because it's easy to
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[fa7acfc] | 35 | find a host distribution for x86, but this edition can be a start point
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| 36 | where you can further modify the instruction for other hardware.</para>
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| 37 |
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| 38 | <sect2>
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| 39 | <title>History of Cross LFS</title>
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| 40 |
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| 41 | <para>A project named <emphasis>Cross Linux From Scratch</emphasis>
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| 42 | was forked from LFS in 2006, by Joe Ciccone, Jim Gifford, and
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| 43 | Ryan Oliver. It has been inactive since 2017. Its history can still
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| 44 | be explored at <ulink url='https://trac.clfs.org/'/>.</para>
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| 45 |
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| 46 | <para>In 2020, Pierre Labastie modified the LFS book to cross-compile
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| 47 | the temporary packages before entering the chroot environment. The main
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| 48 | purpose of this approach was to fix multiple issues found by Iterative
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| 49 | Comparision Analysis. With Pierre's work, the only change needed by
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| 50 | this edition is basically <quote>to reboot instead of chroot</quote>.
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| 51 | However, some additional steps is needed to make the system bootable
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| 52 | at the end of Chapter 6, and setting up an environment suitable for
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| 53 | building and test packages at the start of Chapter 7. Then this Cross
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| 54 | Edition is created to demonstrate these steps.</para>
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[a626665d] | 55 |
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| 56 | <para>Unlike the legacy CLFS project, in the Cross Edition we don't
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| 57 | build any package containing an <command>init</command> process for the
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| 58 | temporary system to boot on the target machine. The temporary system
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| 59 | is booted with a shell running as PID 1, and some necessary jobs of a
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| 60 | normal <command>init</command> process are manually done with commands.
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| 61 | This minimizes the difference from the main LFS book, and also helpful
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| 62 | to learn the initialization steps booting a Linux system.</para>
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[fa7acfc] | 63 | </sect2>
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| 64 |
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| 65 | </sect1>
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