lfs-book/chapter01/how.xml

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<sect1 id="ch-intro-how">
  <?dbhtml filename="how.html"?>

  <title>How to Build an LFS System</title>

  <para>The LFS system will be built by using a previously installed
  Linux distribution (such as Debian, Mandrake, Red Hat, or SuSE). This
  existing Linux system (the host) will be used as a starting point to
  provide necessary programs, including a compiler, linker, and shell,
  to build the new system. Select the <quote>development</quote> option
  during the distribution installation to be able to access these
  tools.</para>

  <para>As an alternative to installing an entire separate distribution
  onto your machine, you may wish to use the Linux From Scratch LiveCD.
  The CD works well as a host system, providing all the tools you need
  to successfully follow the instructions in this book. Additionally,
  it contains all the source packages, patches and a copy of this book.
  So once you have the CD, no network connection or additional downloads
  are necessary. For more information about the LFS LiveCD or to download
  a copy, visit <ulink url="&livecd-root;"/>.</para>

  <para><xref linkend="chapter-partitioning"/> of this book describes how
  to create a new Linux native partition and file system, the place
  where the new LFS system will be compiled and installed. <xref
  linkend="chapter-getting-materials"/> explains which packages and
  patches need to be downloaded to build an LFS system and how to store
  them on the new file system. <xref linkend="chapter-final-preps"/>
  discusses the setup for an appropriate working environment. Please read
  <xref linkend="chapter-final-preps"/> carefully as it explains several
  important issues the developer should be aware of before beginning to
  work through <xref linkend="chapter-temporary-tools"/> and beyond.</para>

  <para><xref linkend="chapter-temporary-tools"/> explains the
  installation of a number of packages that will form the basic
  development suite (or toolchain) which is used to build the actual
  system in <xref linkend="chapter-building-system"/>. Some of these
  packages are needed to resolve circular dependencies&mdash;for example,
  to compile a compiler, you need a compiler.</para>

  <para><xref linkend="chapter-temporary-tools"/> also shows the user how to
  build a first pass of the toolchain, including Binutils and GCC (first pass
  basically means these two core packages will be re-installed a second time).
  The next step is to build Glibc, the C library. Glibc will be compiled by
  the toolchain programs built in the first pass. Then, a second pass of the
  toolchain will be built. This time, the toolchain will be dynamically linked
  against the newly built Glibc. The remaining <xref
  linkend="chapter-temporary-tools"/> packages are built using this second
  pass toolchain. When this is done, the LFS installation process will no
  longer depend on the host distribution, with the exception of the running
  kernel. </para>

  <para>This effort to isolate the new system from the host distribution may
  seem excessive, but a full technical explanation is provided in
  <xref linkend="ch-tools-toolchaintechnotes"/>.</para>

  <para>In <xref linkend="chapter-building-system"/>, the full LFS system is
  built. The <command>chroot</command> (change root) program is used to enter
  a virtual environment and start a new shell whose root directory will be
  set to the LFS partition. This is very similar to rebooting and instructing
  the kernel to mount the LFS partition as the root partition. The system
  does not actually reboot, but instead <command>chroot</command>'s because
  creating a bootable system requires additional work which is not necessary
  just yet. The major advantage is that <quote>chrooting</quote> allows the
  builder to continue using the host while LFS is being built. While waiting
  for package compilation to complete, a user can switch to a different
  virtual console (VC) or X desktop and continue using the computer as
  normal.</para>

  <para>To finish the installation, the LFS-Bootscripts are set up in
  <xref linkend="chapter-bootscripts"/>, and the kernel and boot loader are set
  up in <xref linkend="chapter-bootable"/>. <xref linkend="chapter-finalizing"/>
  contains information on furthering the LFS experience beyond this book.
  After the steps in this book have been implemented, the computer will be
  ready to reboot into the new LFS system.</para>

  <para>This is the process in a nutshell. Detailed information on each
  step is discussed in the following chapters and package descriptions.
  Items that may seem complicated will be clarified, and everything will
  fall into place as the reader embarks on the LFS adventure.</para>

</sect1>