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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, openSUSE, |
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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 |
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56 | <filename class="directory">/tools</filename>. This minimal system will be |
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57 | built using the cross-toolchain in |
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58 | <filename class="directory">/cross-tools</filename>.</para> |
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59 | |
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60 | <para>In <xref linkend="chapter-building-system"/>, the full CLFS system is |
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61 | built. Depending on the system you are cross-compiling for, you will either |
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62 | boot the minimal temp-system on the target machine, or chroot into it.</para> |
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63 | |
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64 | <para>The <command>chroot</command> (change root) program is used to enter |
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65 | a virtual environment and start a new shell whose root directory will be set |
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66 | to the CLFS partition. This is very similar to rebooting and instructing the |
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67 | kernel to mount the CLFS partition as the root partition. |
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68 | The major advantage is that <quote>chrooting</quote> allows the builder to |
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69 | continue using the host while CLFS is being built. While waiting for package |
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70 | compilation to complete, a user can switch to a different virtual console |
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71 | (VC) or X desktop and continue using the computer as normal.</para> |
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72 | |
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73 | <para>Some systems cannot be built by chrooting so they must be |
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74 | booted instead. Generally, if you building for a different arch than |
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75 | the host system, you must reboot because the kernel will likely not |
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76 | support the target machine. Booting involves installing a few |
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77 | additional packages that are needed for bootup, installing |
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78 | boot-scripts, and building a miminal kernel.<!-- We also describe some |
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79 | alternative booting methods in <xref linkend="ch-boot-whatnext"/> --></para> |
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80 | |
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81 | <para>To finish the installation, several configuration files are created in |
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82 | <xref linkend="chapter-system-config"/>, and the kernel and boot loader are set |
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83 | up in <xref linkend="chapter-bootable"/>. <xref linkend="chapter-finalizing"/> |
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84 | contains information on furthering the CLFS experience beyond this book. |
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85 | After the steps in this book have been implemented, the computer will be |
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86 | ready to reboot into the new CLFS system.</para> |
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87 | |
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88 | <para>This is the process in a nutshell. Detailed information on each |
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89 | step is discussed in the following chapters and package descriptions. |
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90 | Items that may seem complicated will be clarified, and everything will |
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91 | fall into place as the reader embarks on the CLFS adventure.</para> |
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92 | |
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93 | </sect1> |
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