1 | <?xml version="1.0" encoding="UTF-8"?>
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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-system-introduction">
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9 | <?dbhtml filename="introduction.html"?>
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10 |
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11 | <title>Introduction</title>
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12 |
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13 | <para>In this chapter, we start constructing the LFS system in earnest.
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14 | </para>
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15 |
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16 | <para>The installation of this software is straightforward. Although in many
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17 | cases the installation instructions could be made shorter and more generic,
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18 | we have opted to provide the full instructions for every package to minimize
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19 | the possibilities for mistakes. The key to learning what makes a Linux system
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20 | work is to know what each package is used for and why you (or the system)
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21 | may need it.</para>
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22 |
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23 | <para>We do not recommend using customized optimizations. They can make
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24 | a program run slightly faster, but they may also cause compilation
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25 | difficulties, and problems when running the program. If a package refuses to
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26 | compile with a customized optimization, try to compile it without
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27 | optimization and see if that fixes the problem. Even if the package does compile when using a customized
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28 | optimization, there is the risk it may have been compiled incorrectly because
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29 | of the complex interactions between the code and the build tools. Also note that
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30 | the <option>-march</option> and <option>-mtune</option> options using values
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31 | not specified in the book have not been tested. This may cause problems with
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32 | the toolchain packages (Binutils, GCC and Glibc). The small potential gains
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33 | achieved by customizing compiler optimizations are often outweighed by the risks.
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34 | First-time builders of LFS are encouraged to build without custom
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35 | optimizations.</para>
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36 |
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37 | <para>On the other hand, we keep the optimizations enabled by the default
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38 | configuration of the packages. In addition, we sometimes explicitly enable an
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39 | optimized configuration provided by a package but not enabled by
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40 | default. The package maintainers have already tested these configurations
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41 | and consider them safe, so it's not likely they would break the build.
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42 | Generally the default configuration already enables <option>-O2</option>
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43 | or <option>-O3</option>, so the resulting system will still run very fast
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44 | without any customized optimization, and be stable at the same time.</para>
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45 |
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46 | <para>Before the installation instructions, each installation page provides
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47 | information about the package, including a concise description of what it
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48 | contains, approximately how long it will take to build, and how much disk
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49 | space is required during this building process. Following the installation
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50 | instructions, there is a list of programs and libraries (along with brief
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51 | descriptions) that the package installs.</para>
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52 |
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53 | <note><para>The SBU values and required disk space include test suite data
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54 | for all applicable packages in <xref linkend="chapter-building-system"/>. SBU
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55 | values have been calculated using four CPU cores (-j4) for all
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56 | operations unless specified otherwise.</para></note>
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57 |
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58 | <sect2>
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59 | <title>About Libraries</title>
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60 |
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61 | <para>In general, the LFS editors discourage building and installing static
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62 | libraries. Most static libraries have been made
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63 | obsolete in a modern Linux system. In addition, linking a static library
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64 | into a program can be detrimental. If an update to the library is needed
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65 | to remove a security problem, every program that uses the static library will
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66 | need to be relinked with the new library. Since the use of static libraries
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67 | is not always obvious, the relevant programs (and the procedures needed to
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68 | do the linking) may not even be known.</para>
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69 |
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70 | <para>The procedures in this chapter remove or disable installation of
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71 | most static libraries. Usually this is done by passing a
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72 | <option>--disable-static</option> option to <command>configure</command>.
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73 | In other cases, alternate means are needed. In a few cases, especially
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74 | Glibc and GCC, the use of static libraries remains an essential feature of the
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75 | package building process. </para>
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76 |
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77 | <para>For a more complete discussion of libraries, see
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78 | <ulink url="&blfs-book;introduction/libraries.html">
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79 | Libraries: Static or shared?</ulink> in the BLFS book.</para>
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80 |
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81 | </sect2>
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82 |
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83 | </sect1>
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