1 | <chapter id="chapter05" xreflabel="Chapter 5">
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2 | <title>Constructing a temporary system</title>
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3 | <?dbhtml filename="chapter05.html" dir="chapter05"?>
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4 |
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5 |
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6 | <sect1 id="ch05-introduction">
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7 | <title>Introduction</title>
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8 | <?dbhtml filename="introduction.html" dir="chapter05"?>
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9 |
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10 | <para>In this chapter we will compile and install a minimal
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11 | Linux system. This system will contain just enough tools to be able
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12 | to start constructing the final LFS system in the next chapter.</para>
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13 |
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14 | <para>The building of this minimal system is done in two steps: first we
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15 | build a brand-new and host-independent toolchain (compiler, assembler,
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16 | linker and libraries), and then use this to build all the other essential
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17 | tools.</para>
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18 |
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19 | <para>The files compiled in this chapter will be installed under the
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20 | <filename class="directory">$LFS/tools</filename> directory
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21 | to keep them separate from the files installed in the next chapter.
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22 | Since the packages compiled here are merely temporary, we don't want
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23 | them to pollute the soon-to-be LFS system.</para>
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24 |
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25 | <para>The key to learning what makes a Linux system work is to know
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26 | what each package is used for and why the user or the system needs it.
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27 | For this purpose a short summary of the content of each package is given
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28 | before the actual installation instructions. For a short description of
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29 | each program in a package, please refer to the corresponding section in
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30 | <xref linkend="appendixa"/>.</para>
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31 |
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32 | <para>The build instructions assume that you are using the bash shell. There
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33 | is also a general expectation that you have already unpacked the sources for a
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34 | package and have performed a <userinput>cd</userinput> into the unpacked source
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35 | directory before issuing the build commands.</para>
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36 |
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37 | <para>Several of the packages are patched before compilation, but only when
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38 | the patch is needed to circumvent a problem. Often the patch is needed in
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39 | both this and the next chapter, but sometimes in only one of them. Therefore,
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40 | don't worry when instructions for a downloaded patch seem to be missing.</para>
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41 |
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42 | <para>During the installation of most packages you will
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43 | see all kinds of compiler warnings scroll by on your screen. These are
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44 | normal and can be safely ignored. They are just what they say they are:
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45 | warnings -- mostly about deprecated, but not invalid, use of the C or C++
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46 | syntax. It's just that C standards have changed rather often and some
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47 | packages still use the older standard, which is not really a problem.</para>
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48 |
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49 | <para><emphasis>Unless</emphasis> told not to, you should normally delete the
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50 | source and build directories after installing each package -- for cleanness
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51 | sake and to save space.</para>
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52 |
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53 | <para>Before continuing, make sure the LFS environment variable is set up
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54 | properly by executing the following:</para>
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55 |
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56 | <screen><userinput>echo $LFS</userinput></screen>
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57 |
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58 | <para>Make sure the output shows the path to your LFS partition's mount
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59 | point, which is <filename class="directory">/mnt/lfs</filename> if you
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60 | followed our example.</para>
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61 |
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62 | </sect1>
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63 |
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64 |
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65 | <sect1 id="ch05-toolchaintechnotes">
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66 | <title>Toolchain technical notes</title>
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67 | <?dbhtml filename="toolchaintechnotes.html" dir="chapter05"?>
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68 |
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69 | <para>This section attempts to explain some of the rationale and technical
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70 | details behind the overall build method. It's not essential that you understand
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71 | everything here immediately. Most of it will make sense once you have performed
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72 | an actual build. Feel free to refer back here at any time.</para>
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73 |
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74 | <para>The overall goal of <xref linkend="chapter05"/> is to provide a sane,
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75 | temporary environment that we can chroot into, and from which we can produce a
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76 | clean, trouble-free build of the target LFS system in
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77 | <xref linkend="chapter06"/>. Along the way, we attempt to divorce ourselves
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78 | from the host system as much as possible, and in so doing build a
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79 | self-contained and self-hosted toolchain. It should be noted that the
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80 | build process has been designed in such a way so as to minimize the risks for
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81 | new readers and provide maximum educational value at the same time. In other
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82 | words, more advanced techniques could be used to build the system.</para>
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83 |
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84 | <important>
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85 | <para>Before continuing, you really should be aware of the name of your working
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86 | platform, often also referred to as the <emphasis>target triplet</emphasis>. For
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87 | many folks the target triplet will be, for example:
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88 | <emphasis>i686-pc-linux-gnu</emphasis>. A simple way to determine your target
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89 | triplet is to run the <filename>config.guess</filename> script that comes with
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90 | the source for many packages. Unpack the Binutils sources and run the script:
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91 | <userinput>./config.guess</userinput> and note the output.</para>
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92 |
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93 | <para>You'll also need to be aware of the name of your platform's
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94 | <emphasis>dynamic linker</emphasis>, often also referred to as the
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95 | <emphasis>dynamic loader</emphasis>, not to be confused with the standard linker
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96 | <emphasis>ld</emphasis> that is part of Binutils. The dynamic linker is provided
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97 | by Glibc and has the job of finding and loading the shared libraries needed by a
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98 | program, preparing the program to run and then running it. For most folks, the
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99 | name of the dynamic linker will be <emphasis>ld-linux.so.2</emphasis>. On
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100 | platforms that are less prevalent, the name might be
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101 | <emphasis>ld.so.1</emphasis> and newer 64 bit platforms might even have
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102 | something completely different. You should be able to determine the name
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103 | of your platform's dynamic linker by looking in the
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104 | <filename class="directory">/lib</filename> directory on your host system. A
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105 | surefire way is to inspect a random binary from your host system by running:
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106 | <userinput>'readelf -l <name of binary> | grep interpreter'</userinput>
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107 | and noting the output. The authoritative reference covering all platforms is in
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108 | the <filename>shlib-versions</filename> file in the root of the Glibc source
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109 | tree.</para>
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110 | </important>
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111 |
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112 | <para>Some key technical points of how the <xref linkend="chapter05"/> build
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113 | method works:</para>
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114 |
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115 | <itemizedlist>
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116 | <listitem><para>Similar in principle to cross compiling whereby tools installed
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117 | into the same prefix work in cooperation and thus utilize a little GNU
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118 | "magic".</para></listitem>
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119 |
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120 | <listitem><para>Careful manipulation of the standard linker's library search
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121 | path to ensure programs are linked only against libraries we
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122 | choose.</para></listitem>
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123 |
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124 | <listitem><para>Careful manipulation of <userinput>gcc</userinput>'s
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125 | <emphasis>specs</emphasis> file to tell the compiler which target dynamic
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126 | linker will be used.</para></listitem>
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127 | </itemizedlist>
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128 |
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129 | <para>Binutils is installed first because both GCC and Glibc perform various
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130 | feature tests on the assembler and linker during their respective runs of
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131 | <userinput>./configure</userinput> to determine which software features to enable
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132 | or disable. This is more important than one might first realize. An incorrectly
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133 | configured GCC or Glibc can result in a subtly broken toolchain where the impact
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134 | of such breakage might not show up until near the end of the build of a whole
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135 | distribution. Thankfully, a test suite failure will usually alert us before too
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136 | much time is wasted.</para>
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137 |
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138 | <para>Binutils installs its assembler and linker into two locations,
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139 | <filename class="directory">/tools/bin</filename> and
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140 | <filename class="directory">/tools/$TARGET_TRIPLET/bin</filename>. In reality,
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141 | the tools in one location are hard linked to the other. An important facet of
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142 | the linker is its library search order. Detailed information can be obtained
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143 | from <userinput>ld</userinput> by passing it the <emphasis>--verbose</emphasis>
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144 | flag. For example: <userinput>'ld --verbose | grep SEARCH'</userinput> will
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145 | show you the current search paths and their order. You can see what files are
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146 | actually linked by <userinput>ld</userinput> by compiling a dummy program and
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147 | passing the <emphasis>--verbose</emphasis> switch. For example:
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148 | <userinput>'gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded'</userinput>
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149 | will show you all the files successfully opened during the link.</para>
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150 |
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151 | <para>The next package installed is GCC and during its run of
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152 | <userinput>./configure</userinput> you'll see, for example:</para>
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153 |
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154 | <blockquote><screen>checking what assembler to use... /tools/i686-pc-linux-gnu/bin/as
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155 | checking what linker to use... /tools/i686-pc-linux-gnu/bin/ld</screen></blockquote>
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156 |
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157 | <para>This is important for the reasons mentioned above. It also demonstrates
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158 | that GCC's configure script does not search the $PATH directories to find which
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159 | tools to use. However, during the actual operation of <userinput>gcc</userinput>
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160 | itself, the same search paths are not necessarily used. You can find out which
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161 | standard linker <userinput>gcc</userinput> will use by running:
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162 | <userinput>'gcc -print-prog-name=ld'</userinput>.
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163 | Detailed information can be obtained from <userinput>gcc</userinput> by passing
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164 | it the <emphasis>-v</emphasis> flag while compiling a dummy program. For
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165 | example: <userinput>'gcc -v dummy.c'</userinput> will show you detailed
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166 | information about the preprocessor, compilation and assembly stages, including
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167 | <userinput>gcc</userinput>'s include search paths and their order.</para>
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168 |
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169 | <para>The next package installed is Glibc. The most important considerations for
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170 | building Glibc are the compiler, binary tools and kernel headers. The compiler
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171 | is generally no problem as Glibc will always use the <userinput>gcc</userinput>
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172 | found in a $PATH directory. The binary tools and kernel headers can be a little
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173 | more troublesome. Therefore we take no risks and use the available configure
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174 | switches to enforce the correct selections. After the run of
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175 | <userinput>./configure</userinput> you can check the contents of the
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176 | <filename>config.make</filename> file in the
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177 | <filename class="directory">glibc-build</filename> directory for all the
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178 | important details. You'll note some interesting items like the use of
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179 | <userinput>CC="gcc -B/tools/bin/"</userinput> to control which binary tools are
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180 | used, and also the use of the <emphasis>-nostdinc</emphasis> and
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181 | <emphasis>-isystem</emphasis> flags to control the compiler's include search
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182 | path. These items help to highlight an important aspect of the Glibc package:
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183 | it is very self-sufficient in terms of its build machinery and generally does
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184 | not rely on toolchain defaults.</para>
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185 |
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186 | <para>After the Glibc installation, we make some adjustments to ensure that
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187 | searching and linking take place only within our <filename>/tools</filename>
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188 | prefix. We install an adjusted <userinput>ld</userinput>, which has a hard-wired
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189 | search path limited to <filename class="directory">/tools/lib</filename>. Then
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190 | we amend <userinput>gcc</userinput>'s specs file to point to our new dynamic
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191 | linker in <filename class="directory">/tools/lib</filename>. This last step is
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192 | <emphasis>vital</emphasis> to the whole process. As mentioned above, a
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193 | hard-wired path to a dynamic linker is embedded into every ELF shared
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194 | executable. You can inspect this by running:
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195 | <userinput>'readelf -l <name of binary> | grep interpreter'</userinput>.
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196 | By amending <userinput>gcc</userinput>'s specs file, we are ensuring that every
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197 | program compiled from here through the end of <xref linkend="chapter05"/> will
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198 | use our new dynamic linker in
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199 | <filename class="directory">/tools/lib</filename>.</para>
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200 |
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201 | <para>The need to use the new dynamic linker is also the reason why we apply the
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202 | Specs patch for the second pass of GCC. Failure to do so will result in the GCC
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203 | programs themselves having the name of the dynamic linker from the host system's
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204 | <filename class="directory">/lib</filename> directory embedded into them, which
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205 | would defeat our goal of getting away from the host.</para>
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206 |
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207 | <para>During the second pass of Binutils, we are able to utilize the
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208 | <emphasis>--with-lib-path</emphasis> configure switch to control
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209 | <userinput>ld</userinput>'s library search path. From this point onwards, the
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210 | core toolchain is self-contained and self-hosted. The remainder of the
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211 | <xref linkend="chapter05"/> packages all build against the new Glibc in
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212 | <filename class="directory">/tools</filename> and all is well.</para>
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213 |
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214 | <para>Upon entering the chroot environment in <xref linkend="chapter06"/>, the
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215 | first major package we install is Glibc, due to its self-sufficient nature that
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216 | we mentioned above. Once this Glibc is installed into
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217 | <filename class="directory">/usr</filename>, we perform a quick changeover of
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218 | the toolchain defaults, then proceed for real in building the rest of the
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219 | target <xref linkend="chapter06"/> LFS system.</para>
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220 |
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221 | <sect2>
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222 | <title>Notes on static linking</title>
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223 |
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224 | <para>Most programs have to perform, beside their specific task, many rather
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225 | common and sometimes trivial operations. These include allocating memory,
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226 | searching directories, reading and writing files, string handling, pattern
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227 | matching, arithmetic and many other tasks. Instead of obliging each program to
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228 | reinvent the wheel, the GNU system provides all these basic functions in
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229 | ready-made libraries. The major library on any Linux system is
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230 | <emphasis>Glibc</emphasis>.</para>
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231 |
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232 | <para>There are two primary ways of linking the functions from a library to a
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233 | program that uses them: statically or dynamically. When a program is linked
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234 | statically, the code of the used functions is included in the executable,
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235 | resulting in a rather bulky program. When a program is dynamically linked, what
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236 | is included is a reference to the dynamic linker, the name of the library, and
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237 | the name of the function, resulting in a much smaller executable. (A third way
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238 | is to use the programming interface of the dynamic linker. See the
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239 | <emphasis>dlopen</emphasis> man page for more information.)</para>
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240 |
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241 | <para>Dynamic linking is the default on Linux and has three major advantages
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242 | over static linking. First, you need only one copy of the executable library
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243 | code on your hard disk, instead of having many copies of the same code included
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244 | into a whole bunch of programs -- thus saving disk space. Second, when several
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245 | programs use the same library function at the same time, only one copy of the
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246 | function's code is required in core -- thus saving memory space. Third, when a
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247 | library function gets a bug fixed or is otherwise improved, you only need to
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248 | recompile this one library, instead of having to recompile all the programs that
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249 | make use of the improved function.</para>
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250 |
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251 | <para>If dynamic linking has several advantages, why then do we statically link
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252 | the first two packages in this chapter? The reasons are threefold: historical,
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253 | educational, and technical. Historical, because earlier versions of LFS
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254 | statically linked every program in this chapter. Educational, because knowing
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255 | the difference is useful. Technical, because we gain an element of independence
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256 | from the host in doing so, meaning that those programs can be used
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257 | independently of the host system. However, it's worth noting that an overall
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258 | successful LFS build can still be achieved when the first two packages are
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259 | built dynamically.</para>
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260 |
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261 | </sect2>
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262 |
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263 | </sect1>
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264 |
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265 |
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266 | <sect1 id="ch05-creatingtoolsdir">
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267 | <title>Creating the $LFS/tools directory</title>
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268 | <?dbhtml filename="creatingtoolsdir.html" dir="chapter05"?>
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269 |
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270 | <para>All programs compiled in this chapter will be installed under <filename
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271 | class="directory">$LFS/tools</filename> to keep them separate from the
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272 | programs compiled in the next chapter. The programs compiled here are only
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273 | temporary tools and won't be a part of the final LFS system and by keeping them
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274 | in a separate directory, we can later easily throw them away.</para>
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275 |
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276 | <para>If later you wish to search through the binaries of your system to see
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277 | what files they make use of or link against, then to make this searching easier
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278 | you may want to choose a unique name. Instead of the simple "tools" you could
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279 | use something like "tools-for-lfs". However, you'll need to be careful to
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280 | adjust all references to "tools" throughout the book including those in any
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281 | patches, the most notable being the GCC Specs Patch.</para>
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282 |
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283 | <para>Create the required directory by running the following:</para>
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284 |
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285 | <screen><userinput>mkdir $LFS/tools</userinput></screen>
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286 |
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287 | <para>The next step is to create a <filename>/tools</filename> symlink on
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288 | your host system. It will point to the directory we just created on the LFS
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289 | partition:</para>
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290 |
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291 | <screen><userinput>ln -s $LFS/tools /</userinput></screen>
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292 |
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293 | <para>This symlink enables us to compile our toolchain so that it always
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294 | refers to <filename>/tools</filename>, meaning that the compiler, assembler
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295 | and linker will work both in this chapter (when we are still using some tools
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296 | from the host) <emphasis>and</emphasis> in the next (when we are chrooted to
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297 | the LFS partition).</para>
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298 |
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299 | <note><para>Study the above command closely. It can be confusing at first
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300 | glance. The <userinput>ln</userinput> command has several syntax variations,
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301 | so be sure to check the ln man page before reporting what you may think is an
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302 | error.</para></note>
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303 |
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304 | </sect1>
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305 |
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306 |
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307 | <sect1 id="ch05-addinguser">
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308 | <title>Adding the user lfs</title>
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309 | <?dbhtml filename="addinguser.html" dir="chapter05"?>
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310 |
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311 | <para>When logged in as <emphasis>root</emphasis>, making a single mistake
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312 | can damage or even wreck your system. Therefore we recommend that you
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313 | build the packages in this chapter as an unprivileged user. You could
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314 | of course use your own user name, but to make it easier to set up a clean
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315 | work environment we'll create a new user <emphasis>lfs</emphasis> and
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316 | use this one during the installation process. As <emphasis>root</emphasis>,
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317 | issue the following commands to add the new user:</para>
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318 |
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319 | <screen><userinput>useradd -s /bin/bash -m lfs
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320 | passwd lfs</userinput></screen>
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321 |
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322 | <para>Now grant this new user <emphasis>lfs</emphasis> full access to
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323 | <filename class="directory">$LFS/tools</filename> by giving it ownership
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324 | of the directory:</para>
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325 |
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326 | <screen><userinput>chown lfs $LFS/tools</userinput></screen>
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327 |
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328 | <para>If you made a separate working directory as suggested, give user
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329 | <emphasis>lfs</emphasis> ownership of this directory too:</para>
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330 |
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331 | <screen><userinput>chown lfs $LFS/sources</userinput></screen>
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332 |
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333 | <para>Next, login as user <emphasis>lfs</emphasis>. This can be done via a
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334 | virtual console, through a display manager, or with the following substitute
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335 | user command:</para>
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336 |
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337 | <screen><userinput>su - lfs</userinput></screen>
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338 |
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339 | <para>The "<userinput>-</userinput>" instructs <userinput>su</userinput> to
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340 | start a new, clean shell.</para>
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341 |
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342 | </sect1>
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343 |
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344 |
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345 | <sect1 id="ch05-settingenviron">
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346 | <title>Setting up the environment</title>
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347 | <?dbhtml filename="settingenvironment.html" dir="chapter05"?>
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348 |
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349 | <para>We're going to set up a good working environment by creating two new
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350 | startup files for the Bash shell. While logged in as user
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351 | <emphasis>lfs</emphasis>, issue the following commands to create a new
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352 | <filename>.bash_profile</filename>:</para>
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353 |
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354 | <screen><userinput>cat > ~/.bash_profile << "EOF"</userinput>
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355 | exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
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356 | <userinput>EOF</userinput></screen>
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357 |
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358 | <para>The
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359 | <userinput>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</userinput>
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360 | command creates a new instance of Bash with a completely empty environment,
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361 | except for the HOME, TERM and PS1 variables. This is needed to ensure that no
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362 | unwanted and potentially hazardous environment variables from the host system
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363 | leak into our build environment. The technique used here is a little
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364 | non-standard but it achieves the goal of enforcing a clean environment. By way
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365 | of explanation, the initial shell is a <emphasis>login</emphasis> shell which
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366 | reads the <filename>.bash_profile</filename>. The new shell instance is a
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367 | <emphasis>non-login</emphasis> shell which reads the
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368 | <filename>.bashrc</filename> (created next).</para>
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369 |
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370 | <para>Now create a new <filename>.bashrc</filename>:</para>
|
---|
371 |
|
---|
372 | <screen><userinput>cat > ~/.bashrc << "EOF"</userinput>
|
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373 | set +h
|
---|
374 | umask 022
|
---|
375 | LFS=/mnt/lfs
|
---|
376 | LC_ALL=POSIX
|
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377 | PATH=/tools/bin:/bin:/usr/bin
|
---|
378 | export LFS LC_ALL PATH
|
---|
379 | <userinput>EOF</userinput></screen>
|
---|
380 |
|
---|
381 | <para>The <userinput>set +h</userinput> command turns off
|
---|
382 | <userinput>bash</userinput>'s hash function. Normally hashing is a useful
|
---|
383 | feature: <userinput>bash</userinput> uses a hash table to remember the
|
---|
384 | full pathnames of executable files to avoid searching the PATH time and time
|
---|
385 | again to find the same executable. However, we'd like the new tools to be
|
---|
386 | used as soon as they are installed. By switching off the hash function, our
|
---|
387 | "interactive" commands (<userinput>make</userinput>,
|
---|
388 | <userinput>patch</userinput>, <userinput>sed</userinput>,
|
---|
389 | <userinput>cp</userinput> and so forth) will always use
|
---|
390 | the newest available version during the build process.</para>
|
---|
391 |
|
---|
392 | <para>Setting the user file-creation mask to 022 ensures that newly created
|
---|
393 | files and directories are only writable for their owner, but readable and
|
---|
394 | executable for anyone.</para>
|
---|
395 |
|
---|
396 | <para>The LFS variable should of course be set to the mount point you
|
---|
397 | chose.</para>
|
---|
398 |
|
---|
399 | <para>The LC_ALL variable controls the localization of certain programs,
|
---|
400 | making their messages follow the conventions of a specified country. If your
|
---|
401 | host system uses a version of Glibc older than 2.2.4,
|
---|
402 | having LC_ALL set to something other than "POSIX" or "C" during this chapter
|
---|
403 | may cause trouble if you exit the chroot environment and wish to return later.
|
---|
404 | By setting LC_ALL to "POSIX" (or "C", the two are equivalent) we ensure that
|
---|
405 | everything will work as expected in the chroot environment.</para>
|
---|
406 |
|
---|
407 | <para>We prepend <filename>/tools/bin</filename> to the standard PATH so
|
---|
408 | that, as we move along through this chapter, the tools we build will get used
|
---|
409 | during the rest of the building process.</para>
|
---|
410 |
|
---|
411 | <para>Finally, source the just-created profile so that we're all set to begin
|
---|
412 | building the temporary tools that will support us in later chapters.</para>
|
---|
413 |
|
---|
414 | <screen><userinput>source ~/.bash_profile</userinput></screen>
|
---|
415 |
|
---|
416 | </sect1>
|
---|
417 |
|
---|
418 |
|
---|
419 | &c5-binutils-pass1;
|
---|
420 | &c5-gcc-pass1;
|
---|
421 | &c5-kernelheaders;
|
---|
422 | &c5-glibc;
|
---|
423 |
|
---|
424 |
|
---|
425 | <sect1 id="ch05-locking-glibc">
|
---|
426 | <title>"Locking in" Glibc</title>
|
---|
427 | <?dbhtml filename="lockingglibc.html" dir="chapter05"?>
|
---|
428 |
|
---|
429 | <para>Now that the temporary C libraries have been installed, we want all
|
---|
430 | the tools compiled in the rest of this chapter to be linked against these
|
---|
431 | libraries. To accomplish this, we need to adjust the linker and the compiler's
|
---|
432 | specs file.</para>
|
---|
433 |
|
---|
434 | <para>First install the adjusted linker by running the following from within
|
---|
435 | the <filename class="directory">binutils-build</filename> directory:</para>
|
---|
436 |
|
---|
437 | <screen><userinput>make -C ld install</userinput></screen>
|
---|
438 |
|
---|
439 | <para>The linker was adjusted a little while back, at the end of the first
|
---|
440 | pass of Binutils. From this point onwards everything will link <emphasis>only
|
---|
441 | </emphasis> against the libraries in <filename>/tools/lib</filename>.</para>
|
---|
442 |
|
---|
443 | <note><para>If you somehow missed the earlier warning to retain the Binutils
|
---|
444 | source and build directories from the first pass or otherwise accidentally
|
---|
445 | deleted them or just don't have access to them, don't worry, all is not lost.
|
---|
446 | Just ignore the above command. The result is a small chance of subsequent
|
---|
447 | programs linking against libraries on the host. This is not ideal, however,
|
---|
448 | it's not a major problem. The situation is corrected when we install the
|
---|
449 | second pass of Binutils later on.</para></note>
|
---|
450 |
|
---|
451 | <para>Now that the adjusted linker is installed, you have to remove the
|
---|
452 | Binutils build and source directories.</para>
|
---|
453 |
|
---|
454 | <para>The next thing to do is to amend our GCC specs file so that it points
|
---|
455 | to the new dynamic linker. A simple sed will accomplish this:</para>
|
---|
456 |
|
---|
457 | <!-- Ampersands are needed to allow cut and paste -->
|
---|
458 |
|
---|
459 | <screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
|
---|
460 | sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \
|
---|
461 | $SPECFILE > tempspecfile &&
|
---|
462 | mv -f tempspecfile $SPECFILE &&
|
---|
463 | unset SPECFILE</userinput></screen>
|
---|
464 |
|
---|
465 | <para>We recommend that you cut-and-paste the above rather than try and type it
|
---|
466 | all in. Or you can edit the specs file by hand if you want to: just replace any
|
---|
467 | occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</para>
|
---|
468 |
|
---|
469 | <important><para>If you are working on a platform where the name of the dynamic
|
---|
470 | linker is something other than <filename>ld-linux.so.2</filename>, you
|
---|
471 | <emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
|
---|
472 | name of your platform's dynamic linker in the above commands. Refer back to
|
---|
473 | <xref linkend="ch05-toolchaintechnotes"/> if necessary.</para></important>
|
---|
474 |
|
---|
475 | <para>Lastly, there is a possibility that some include files from the host
|
---|
476 | system have found their way into GCC's private include dir. This can happen
|
---|
477 | because of GCC's "fixincludes" process which runs as part of the GCC build.
|
---|
478 | We'll explain more about this further on in this chapter. For now, run the
|
---|
479 | following commands to eliminate this possibility:</para>
|
---|
480 |
|
---|
481 | <screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>
|
---|
482 |
|
---|
483 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
484 | <literallayout></literallayout>
|
---|
485 |
|
---|
486 | <caution><para>It is imperative at this point to stop and ensure that the basic
|
---|
487 | functions (compiling and linking) of the new toolchain are working as expected.
|
---|
488 | For this we are going to perform a simple sanity check:</para>
|
---|
489 |
|
---|
490 | <screen><userinput>echo 'main(){}' > dummy.c
|
---|
491 | gcc dummy.c
|
---|
492 | readelf -l a.out | grep ': /tools'</userinput></screen>
|
---|
493 |
|
---|
494 | <para>If everything is working correctly, there should be no errors, and the
|
---|
495 | output of the last command will be:</para>
|
---|
496 |
|
---|
497 | <blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
|
---|
498 |
|
---|
499 | <para>If you did not receive the output as shown above, or received no output at
|
---|
500 | all, then something is seriously wrong. You will need to investigate and retrace
|
---|
501 | your steps to find out where the problem is and correct it. There is no point in
|
---|
502 | continuing until this is done. Most likely something went wrong with the specs
|
---|
503 | file amendment above. Note especially that <filename>/tools/lib</filename>
|
---|
504 | appears as the prefix of our dynamic linker. Of course, if you are working on a
|
---|
505 | platform where the name of the dynamic linker is something other than
|
---|
506 | <filename>ld-linux.so.2</filename>, then the output will be slightly
|
---|
507 | different.</para>
|
---|
508 |
|
---|
509 | <para>Once you are satisfied that all is well, clean up the test files:</para>
|
---|
510 |
|
---|
511 | <screen><userinput>rm dummy.c a.out</userinput></screen>
|
---|
512 | </caution>
|
---|
513 |
|
---|
514 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
515 | <literallayout></literallayout>
|
---|
516 |
|
---|
517 | <para>This completes the installation of the self-contained toolchain, and it
|
---|
518 | can now be used to build the rest of the temporary tools.</para>
|
---|
519 |
|
---|
520 | </sect1>
|
---|
521 |
|
---|
522 |
|
---|
523 | &c5-tcl;
|
---|
524 | &c5-expect;
|
---|
525 | &c5-dejagnu;
|
---|
526 | &c5-gcc-pass2;
|
---|
527 | &c5-binutils-pass2;
|
---|
528 |
|
---|
529 | &c5-gawk;
|
---|
530 | &c5-coreutils;
|
---|
531 | &c5-bzip2;
|
---|
532 | &c5-gzip;
|
---|
533 | &c5-diffutils;
|
---|
534 | &c5-findutils;
|
---|
535 | &c5-make;
|
---|
536 | &c5-grep;
|
---|
537 | &c5-sed;
|
---|
538 | &c5-gettext;
|
---|
539 | &c5-ncurses;
|
---|
540 | &c5-patch;
|
---|
541 | &c5-tar;
|
---|
542 | &c5-texinfo;
|
---|
543 | &c5-bash;
|
---|
544 | &c5-utillinux;
|
---|
545 | &c5-perl;
|
---|
546 |
|
---|
547 |
|
---|
548 | <sect1 id="ch05-stripping">
|
---|
549 | <title>Stripping</title>
|
---|
550 | <?dbhtml filename="stripping.html" dir="chapter05"?>
|
---|
551 |
|
---|
552 | <para>The steps in this section are optional. If your LFS partition is rather
|
---|
553 | small, you will be glad to learn that you can throw away some unnecessary
|
---|
554 | things. The executables and libraries you have built so far contain about 130 MB
|
---|
555 | of unneeded debugging symbols. Remove those symbols like this:</para>
|
---|
556 |
|
---|
557 | <screen><userinput>strip --strip-unneeded /tools/{,s}bin/*
|
---|
558 | strip --strip-debug /tools/lib/*</userinput></screen>
|
---|
559 |
|
---|
560 | <para>The first of the above commands will skip some twenty files, reporting
|
---|
561 | that it doesn't recognize their file format. Most of them are scripts instead
|
---|
562 | of binaries.</para>
|
---|
563 |
|
---|
564 | <para>Take care <emphasis>not</emphasis> to use
|
---|
565 | <userinput>--strip-unneeded</userinput> on the libraries -- they would be
|
---|
566 | destroyed and you would have to build Glibc all over again.</para>
|
---|
567 |
|
---|
568 | <para>To save another couple of megabytes, you can throw away all the
|
---|
569 | documentation:</para>
|
---|
570 |
|
---|
571 | <screen><userinput>rm -rf /tools/{,share/}{doc,info,man}</userinput></screen>
|
---|
572 |
|
---|
573 | <para>You will now need to have at least 850 MB of free space on your LFS
|
---|
574 | filesystem to be able to build and install Glibc in the next phase. If you can
|
---|
575 | build and install Glibc, you can build and install the rest too.</para>
|
---|
576 |
|
---|
577 | </sect1>
|
---|
578 |
|
---|
579 | </chapter>
|
---|
580 |
|
---|