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66 lines
3.2 KiB
XML
66 lines
3.2 KiB
XML
<?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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<sect1 id="pre-cross">
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<?dbhtml filename="cross.html"?>
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<title>About the Cross Edition</title>
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<para>While LFS has provided an approach to build a Linux system entirely
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from source code, it builds the LFS system in a
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<emphasis>chroot</emphasis> environment. The chroot environment is almost
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seperate from the host distribution, but it still relies on the hardware
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and Linux kernel from the host system.</para>
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<para>The Cross Edition contains modification to the LFS book, allowing
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to boot the temporary system instead of chroot. So it's possible to
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bootstrap a Linux system for a target where no Linux distribution exists.
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And, the kernel ABI may frequently change at the early stage porting Linux
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to a new hardware. The modification in this edition completely removes
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the dependency on the kernel from the host distribution, allowing to
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rebuild the entire system with a new kernel ABI.</para>
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<para>If you already have a Linux distribution running on the hardware
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where you need a Linux From Scratch system, with the kernel ABI you want,
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and it's compatible with the Host System Requirements specified by the
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LFS book, it's likely you should read the original LFS book instead of
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this edition.</para>
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<para>This edition contains instructions to bootstrap a Linux system for
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x86 (32-bit or 64-bit). It may look irrational because it's easy to
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find a host distribution for x86, but this edition can be a start point
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where you can further modify the instruction for other hardware.</para>
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<sect2>
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<title>History of Cross LFS</title>
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<para>A project named <emphasis>Cross Linux From Scratch</emphasis>
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was forked from LFS in 2006, by Joe Ciccone, Jim Gifford, and
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Ryan Oliver. It has been inactive since 2017. Its history can still
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be explored at <ulink url='https://trac.clfs.org/'/>.</para>
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<para>In 2020, Pierre Labastie modified the LFS book to cross-compile
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the temporary packages before entering the chroot environment. The main
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purpose of this approach was to fix multiple issues found by Iterative
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Comparision Analysis. With Pierre's work, the only change needed by
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this edition is basically <quote>to reboot instead of chroot</quote>.
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However, some additional steps is needed to make the system bootable
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at the end of Chapter 6, and setting up an environment suitable for
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building and test packages at the start of Chapter 7. Then this Cross
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Edition is created to demonstrate these steps.</para>
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<para>Unlike the legacy CLFS project, in the Cross Edition we don't
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build any package containing an <command>init</command> process for the
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temporary system to boot on the target machine. The temporary system
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is booted with a shell running as PID 1, and some necessary jobs of a
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normal <command>init</command> process are manually done with commands.
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This minimizes the difference from the main LFS book, and also helpful
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to learn the initialization steps booting a Linux system.</para>
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</sect2>
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</sect1>
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