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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34 | x86 (32-bit or 64-bit). It may look irrational because it's easy to
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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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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 it's also
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62 | helpful for learning the initialization steps booting a Linux
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63 | system.</para>
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64 | </sect2>
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65 |
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66 | </sect1>
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