source: clfs-sysroot/BOOK/introduction/common/how.xml @ 2ad9b71

Last change on this file since 2ad9b71 was 2ad9b71, checked in by Jim Gifford <clfs@…>, 13 years ago

r3907@server (orig r1758): jciccone | 2006-06-09 17:17:08 -0700
Removed the need for /cross-tools, using /cross-tools now.

  • Property mode set to 100644
File size: 5.7 KB
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
3  "" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
8<sect1 id="ch-intro-how">
9  <?dbhtml filename="how.html"?>
11  <title>How to Build a CLFS System</title>
13  <para>The CLFS system will be built by using a previously installed
14  Linux distribution (such as Debian, Mandrake, Red Hat, or SuSE). This
15  existing Linux system (the host) will be used as a starting point to
16  provide necessary programs, including a compiler, linker, and shell,
17  to build the new system. Select the <quote>development</quote> option
18  during the distribution installation to be able to access these
19  tools.</para>
21  <para>As an alternative to installing an entire separate distribution
22  onto your machine, you may wish to
23  use the Linux From Scratch LiveCD. The CD works well as a host system,
24  providing all the tools you need to successfully follow the instructions
25  in this book. Additionally, it contains all the source packages, patches
26  and a copy of this book. So once you have the CD, no network connection
27  or additional downloads are necessary. For more information about the
28  LFS LiveCD or to download a copy, visit <ulink url="&livecd-root;"/></para>
30  <!-- -->
33  <para><xref linkend="chapter-partitioning"/> of this book describes how
34  to create a new Linux native partition and file system, the place
35  where the new CLFS system will be compiled and installed. <xref
36  linkend="chapter-getting-materials"/> explains which packages and
37  patches need to be downloaded to build a CLFS system and how to store
38  them on the new file system. <xref linkend="chapter-final-preps"/>
39  discusses the setup for an appropriate working environment. Please read
40  <xref linkend="chapter-final-preps"/> carefully as it explains several
41  important issues the developer should be aware of before beginning to
42  work through <xref linkend="chapter-cross-tools"/> and
43  beyond.</para>
45  <para><xref linkend="chapter-cross-tools"/> explains the installation of
46  cross-compile tools which will be built on the host but be able to compile
47  programs that run on the target machine. These cross-compile tools will
48  be used to create a temporary, minimal system that will be the basis for
49  building the final CLFS system. Some of these packages are needed to resolve
50  circular dependencies&mdash;for example, to compile a compiler, you need a
51  compiler.</para>
53  <para>The process of building cross-compile tools first involves installing
54  binutils into ${LFS}/cross-tools, so that the linker can be used with the building
55  of everything else in the temp-system. GCC is then compiled statically and
56  installed into ${LFS}/cross-tools, and this cross-compiler is used to build glibc
57  into /tools for the temp-system. The GCC cross-compiler is then rebuilt
58  dynamically - this final cross-compiler is what will be used to build the
59  rest of the temporary system. When this is done, the CLFS installation
60  process will no longer depend on the host distribution, with the exception
61  of the running kernel.
62  <!-- still needs some work - needs to provide a better technical
63explanation, especially the reasoning for compiling gcc statically then dynamically... --></para>
65  <para>The packages in <!-- <xref linkend="chapter-temp-system"/> --> are then built
66  using the cross-compiled tools in ${LFS}/cross-tools, and linked against the
67  C library that was installed during the building of the cross-tools.</para>
69  <para>This effort to isolate the new system from the host distribution
70  may seem excessive, but a full technical explanation is provided at the
71  beginning of <!-- <xref linkend="chapter-temp-system"/> -->.</para>
73  <para>In <xref linkend="chapter-building-system"/>, the full CLFS system is
74  built. Depending on the system you are cross-compiling for, either you will
75  boot the minimal temp-system on the target machine, or chroot into it.</para>
77  <para>The <command>chroot</command> (change root) program is used to enter
78  a virtual environment and start a new shell whose root directory will be set
79  to the CLFS partition. This is very similar to rebooting and instructing the
80  kernel to mount the CLFS partition as the root partition.
81  The major advantage is that <quote>chrooting</quote> allows the builder to
82  continue using the host while CLFS is being built. While waiting for package
83  compilation to complete, a user can switch to a different virtual console
84  (VC) or X desktop and continue using the computer as normal.</para>
86  <para>Some systems cannot be built by chrooting so they must be
87  booted instead. Generally, if you building for a different arch than
88  the host system, you must reboot because the kernel will likely not
89  support the target machine. Booting involves installing a few
90  additional packages that are needed for bootup, installing
91  bootscripts, and building a miminal kernel.</para>
93  <para>To finish the installation, the CLFS-Bootscripts are set up in <xref
94  linkend="chapter-bootscripts"/>, and the kernel and boot loader are set
95  up in <xref linkend="chapter-bootable"/>. <xref
96  linkend="chapter-finalizing"/> contains information on furthering the
97  CLFS experience beyond this book.  After the steps in this book have
98  been implemented, the computer will be ready to reboot into the new
99  CLFS system.</para>
100  <!-- -->
102  <para>This is the process in a nutshell. Detailed information on each
103  step is discussed in the following chapters and package descriptions.
104  Items that may seem complicated will be clarified, and everything will
105  fall into place as the reader embarks on the CLFS adventure.</para>
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