| 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="ch-intro-how">
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| 9 | <?dbhtml filename="how.html"?>
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| 10 |
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| 11 | <title>How to Build a CLFS System</title>
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| 12 |
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| 13 | <para>The CLFS system will be built by using a previously installed
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| 14 | Unix system or Linux distribution (such as Debian, Fedora, Mandriva, SUSE,
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| 15 | or Ubuntu). This existing system (the host) will be used as a starting
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| 16 | point to provide necessary programs, including a compiler, linker, and shell,
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| 17 | to build the new system. Select the <quote>development</quote> option
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| 18 | during the distribution installation to be able to access these
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| 19 | tools.</para>
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| 20 |
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| 21 | <para>As an alternative to installing an entire separate distribution onto
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| 22 | your machine, you may wish to use a livecd. Most distributions provide
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| 23 | a livecd, which provides an environment to which you can add the required
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| 24 | tools onto, allowing you to
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| 25 | successfully follow the instructions in this book. Remember that if you
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| 26 | reboot the livecd you will need to reconfigure the host environment before
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| 27 | continuing with your build.</para>
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| 28 |
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| 29 | <para><xref linkend="chapter-partitioning"/> of this book describes how
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| 30 | to create a new Linux native partition and file system, the place
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| 31 | where the new CLFS system will be compiled and installed. <xref
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| 32 | linkend="chapter-getting-materials"/> explains which packages and
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| 33 | patches need to be downloaded to build a CLFS system and how to store
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| 34 | them on the new file system. <xref linkend="chapter-final-preps"/>
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| 35 | discusses the setup for an appropriate working environment. Please read
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| 36 | <xref linkend="chapter-final-preps"/> carefully as it explains several
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| 37 | important issues the developer should be aware of before beginning to
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| 38 | work through <xref linkend="chapter-cross-tools"/> and
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| 39 | beyond.</para>
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| 40 |
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| 41 | <para><xref linkend="chapter-cross-tools"/> explains the installation of
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| 42 | cross-compile tools which will be built on the host but be able to compile
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| 43 | programs that run on the target machine. These cross-compile tools will
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| 44 | be used to create a temporary, minimal system that will be the basis for
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| 45 | building the final CLFS system. Some of these packages are needed to resolve
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| 46 | circular dependencies—for example, to compile a compiler, you need a
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| 47 | compiler.</para>
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| 48 |
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| 49 | <para>The process of building cross-compile tools first involves building and
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| 50 | installing all the necessary tools to create a build system for the target
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| 51 | machine. With these cross-compiled tools, we eliminate any
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| 52 | dependencies on the toolchain from our host distro.</para>
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| 53 |
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| 54 | <para>After we build our <quote>Cross-Tools</quote>, we start building
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| 55 | a very minimal working system in /tools. This minimal system will be built
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| 56 | using the cross-toolchain in /cross-tools.</para>
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| 57 |
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| 58 | <para>In <xref linkend="chapter-building-system"/>, the full CLFS system is
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| 59 | built. Depending on the system you are cross-compiling for, you will either
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| 60 | boot the minimal temp-system on the target machine, or chroot into it.</para>
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| 61 |
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| 62 | <para>The <command>chroot</command> (change root) program is used to enter
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| 63 | a virtual environment and start a new shell whose root directory will be set
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| 64 | to the CLFS partition. This is very similar to rebooting and instructing the
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| 65 | kernel to mount the CLFS partition as the root partition.
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| 66 | The major advantage is that <quote>chrooting</quote> allows the builder to
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| 67 | continue using the host while CLFS is being built. While waiting for package
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| 68 | compilation to complete, a user can switch to a different virtual console
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| 69 | (VC) or X desktop and continue using the computer as normal.</para>
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| 70 |
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| 71 | <para>Some systems cannot be built by chrooting so they must be
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| 72 | booted instead. Generally, if you building for a different arch than
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| 73 | the host system, you must reboot because the kernel will likely not
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| 74 | support the target machine. Booting involves installing a few
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| 75 | additional packages that are needed for bootup, installing
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| 76 | boot-scripts, and building a miminal kernel. We also describe some
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| 77 | alternative booting methods in <xref linkend="ch-boot-whatnext"/></para>
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| 78 |
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| 79 | <para>To finish the installation, several configuration files are created in
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| 80 | <xref linkend="chapter-system-config"/>, and the kernel and boot loader are set
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| 81 | up in <xref linkend="chapter-bootable"/>. <xref linkend="chapter-finalizing"/>
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| 82 | contains information on furthering the CLFS experience beyond this book.
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| 83 | After the steps in this book have been implemented, the computer will be
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| 84 | ready to reboot into the new CLFS system.</para>
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| 85 |
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| 86 | <para>This is the process in a nutshell. Detailed information on each
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| 87 | step is discussed in the following chapters and package descriptions.
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| 88 | Items that may seem complicated will be clarified, and everything will
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| 89 | fall into place as the reader embarks on the CLFS adventure.</para>
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| 90 |
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| 91 | </sect1>
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