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<!ENTITY % general-entities SYSTEM "../general.ent">
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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—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>
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