source: prologue/cross.xml@ a626665d

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<sect1 id="pre-cross">
  <?dbhtml filename="cross.html"?>

  <title>About the Cross Edition</title>

  <para>While LFS has provided an approach to build a Linux system entirely
  from source code, it builds the LFS system in a
  <emphasis>chroot</emphasis> environment.  The chroot environment is almost
  seperate from the host distribution, but it still relies on the hardware
  and Linux kernel from the host system.</para>

  <para>The Cross Edition contains modification to the LFS book, allowing
  to boot the temporary system instead of chroot.  So it's possible to
  bootstrap a Linux system for a target where no Linux distribution exists.
  And, the kernel ABI may frequently change at the early stage porting Linux
  to a new hardware.  The modification in this edition completely removes
  the dependency on the kernel from the host distribution, allowing to
  rebuild the entire system with a new kernel ABI.</para>

  <para>If you already have a Linux distribution running on the hardware
  where you need a Linux From Scratch system, with the kernel ABI you want,
  and it's compatible with the Host System Requirements specified by the
  LFS book, it's likely you should read the original LFS book instead of
  this edition.</para>

  <para>This edition contains instructions to bootstrap a Linux system for
  x86 (32-bit or 64-bit).  It may looks irrational because it's easy to
  find a host distribution for x86, but this edition can be a start point
  where you can further modify the instruction for other hardware.</para>

  <sect2>
    <title>History of Cross LFS</title>

    <para>A project named <emphasis>Cross Linux From Scratch</emphasis>
    was forked from LFS in 2006, by Joe Ciccone, Jim Gifford, and
    Ryan Oliver.  It has been inactive since 2017.  Its history can still
    be explored at <ulink url='https://trac.clfs.org/'/>.</para>

    <para>In 2020, Pierre Labastie modified the LFS book to cross-compile
    the temporary packages before entering the chroot environment.  The main
    purpose of this approach was to fix multiple issues found by Iterative
    Comparision Analysis.  With Pierre's work, the only change needed by
    this edition is basically <quote>to reboot instead of chroot</quote>.
    However, some additional steps is needed to make the system bootable
    at the end of Chapter 6, and setting up an environment suitable for
    building and test packages at the start of Chapter 7.  Then this Cross
    Edition is created to demonstrate these steps.</para>

    <para>Unlike the legacy CLFS project, in the Cross Edition we don't
    build any package containing an <command>init</command> process for the
    temporary system to boot on the target machine.  The temporary system
    is booted with a shell running as PID 1, and some necessary jobs of a
    normal <command>init</command> process are manually done with commands.
    This minimizes the difference from the main LFS book, and also helpful
    to learn the initialization steps booting a Linux system.</para>
  </sect2>

</sect1>