[7f1fcd8] | 1 | <chapter id="chapter05" xreflabel="Chapter 5">
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[35c2fa60] | 2 | <title>Constructing a temporary system</title>
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[9ac3d35] | 3 | <?dbhtml filename="chapter05.html" dir="chapter05"?>
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[6370fa6] | 4 |
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[cfabeed] | 5 |
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[3be4d97] | 6 | <sect1 id="ch-tools-introduction">
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[cfabeed] | 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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[878b2a4b] | 25 | <para>Before issuing the build instructions for a package you are expected to
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| 26 | have already unpacked it as user <emphasis>lfs</emphasis> (explained shortly),
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| 27 | and to have performed a <userinput>cd</userinput> into the created directory.
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| 28 | The build instructions assume that you are using the <command>bash</command>
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| 29 | shell.</para>
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[cfabeed] | 30 |
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| 31 | <para>Several of the packages are patched before compilation, but only when
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| 32 | the patch is needed to circumvent a problem. Often the patch is needed in
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| 33 | both this and the next chapter, but sometimes in only one of them. Therefore,
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[878b2a4b] | 34 | don't worry when instructions for a downloaded patch seem to be missing. Also,
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| 35 | when applying a patch, you'll occasionally see warning messages about
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[b05a831] | 36 | <emphasis>offset</emphasis> or <emphasis>fuzz</emphasis>. These warnings are
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[878b2a4b] | 37 | nothing to worry about, as the patch was still successfully applied.</para>
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| 38 |
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| 39 | <para>During the compilation of most packages you will see many warnings
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| 40 | scroll by on your screen. These are normal and can safely be ignored. They are
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| 41 | just what they say they are: warnings -- mostly about deprecated, but not
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| 42 | invalid, use of the C or C++ syntax. It's just that C standards have changed
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| 43 | rather often and some packages still use the older standard, which is not
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| 44 | really a problem.</para>
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| 45 |
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| 46 | <para>After installing each package you should delete its source and build
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| 47 | directories, <emphasis>unless</emphasis> told otherwise. Deleting the sources
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| 48 | saves space, but also prevents misconfiguration when the same package is
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| 49 | reinstalled further on. Only for three packages you will need to keep the
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| 50 | source and build directories around for a while, so their contents can be used
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| 51 | by later commands. Do not miss the reminders.</para>
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| 52 |
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| 53 | <para>Now first check that your LFS environment variable is set up
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| 54 | properly:</para>
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[cfabeed] | 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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[3be4d97] | 65 | <sect1 id="ch-tools-toolchaintechnotes">
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[cfabeed] | 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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[f4993cf] | 87 | many folks the target triplet will probably be
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[cfabeed] | 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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[f4993cf] | 98 | program, preparing the program to run and then running it. For most folks the
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[cfabeed] | 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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[90e3cb3] | 106 | <userinput>readelf -l <name of binary> | grep interpreter</userinput>
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[cfabeed] | 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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[90e3cb3] | 124 | <listitem><para>Careful manipulation of <command>gcc</command>'s
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[cfabeed] | 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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[90e3cb3] | 131 | <command>./configure</command> to determine which software features to enable
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[cfabeed] | 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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[90e3cb3] | 143 | from <command>ld</command> by passing it the <emphasis>--verbose</emphasis>
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| 144 | flag. For example: <command>ld --verbose | grep SEARCH</command> will
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[cfabeed] | 145 | show you the current search paths and their order. You can see what files are
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[90e3cb3] | 146 | actually linked by <command>ld</command> by compiling a dummy program and
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| 147 | passing the <emphasis>--verbose</emphasis> switch to the linker. For example:
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| 148 | <command>gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded</command>
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| 149 | will show you all the files successfully opened during the linking.</para>
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[cfabeed] | 150 |
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| 151 | <para>The next package installed is GCC and during its run of
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[90e3cb3] | 152 | <command>./configure</command> you'll see, for example:</para>
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[cfabeed] | 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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[90e3cb3] | 159 | tools to use. However, during the actual operation of <command>gcc</command>
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[cfabeed] | 160 | itself, the same search paths are not necessarily used. You can find out which
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[90e3cb3] | 161 | standard linker <command>gcc</command> will use by running:
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| 162 | <command>gcc -print-prog-name=ld</command>.
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| 163 | Detailed information can be obtained from <command>gcc</command> by passing
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[cfabeed] | 164 | it the <emphasis>-v</emphasis> flag while compiling a dummy program. For
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[90e3cb3] | 165 | example: <command>gcc -v dummy.c</command> will show you detailed
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[cfabeed] | 166 | information about the preprocessor, compilation and assembly stages, including
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[90e3cb3] | 167 | <command>gcc</command>'s include search paths and their order.</para>
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[cfabeed] | 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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[90e3cb3] | 171 | is generally no problem as Glibc will always use the <command>gcc</command>
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[cfabeed] | 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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[90e3cb3] | 175 | <command>./configure</command> you can check the contents of the
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[cfabeed] | 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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[90e3cb3] | 179 | <emphasis>CC="gcc -B/tools/bin/"</emphasis> to control which binary tools are
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[cfabeed] | 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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[90e3cb3] | 188 | prefix. We install an adjusted <command>ld</command>, which has a hard-wired
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[cfabeed] | 189 | search path limited to <filename class="directory">/tools/lib</filename>. Then
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[90e3cb3] | 190 | we amend <command>gcc</command>'s specs file to point to our new dynamic
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[cfabeed] | 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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[90e3cb3] | 195 | <command>readelf -l <name of binary> | grep interpreter</command>.
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| 196 | By amending <command>gcc</command>'s specs file, we are ensuring that every
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| 197 | program compiled from here through the end of this chapter will use our new
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| 198 | dynamic linker in <filename class="directory">/tools/lib</filename>.</para>
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[cfabeed] | 199 |
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| 200 | <para>The need to use the new dynamic linker is also the reason why we apply the
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| 201 | Specs patch for the second pass of GCC. Failure to do so will result in the GCC
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| 202 | programs themselves having the name of the dynamic linker from the host system's
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| 203 | <filename class="directory">/lib</filename> directory embedded into them, which
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| 204 | would defeat our goal of getting away from the host.</para>
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| 205 |
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| 206 | <para>During the second pass of Binutils, we are able to utilize the
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| 207 | <emphasis>--with-lib-path</emphasis> configure switch to control
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[90e3cb3] | 208 | <command>ld</command>'s library search path. From this point onwards, the
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[cfabeed] | 209 | core toolchain is self-contained and self-hosted. The remainder of the
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| 210 | <xref linkend="chapter05"/> packages all build against the new Glibc in
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| 211 | <filename class="directory">/tools</filename> and all is well.</para>
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| 212 |
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| 213 | <para>Upon entering the chroot environment in <xref linkend="chapter06"/>, the
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| 214 | first major package we install is Glibc, due to its self-sufficient nature that
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| 215 | we mentioned above. Once this Glibc is installed into
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| 216 | <filename class="directory">/usr</filename>, we perform a quick changeover of
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| 217 | the toolchain defaults, then proceed for real in building the rest of the
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[90e3cb3] | 218 | target LFS system.</para>
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[cfabeed] | 219 |
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| 220 | <sect2>
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| 221 | <title>Notes on static linking</title>
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| 222 |
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| 223 | <para>Most programs have to perform, beside their specific task, many rather
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| 224 | common and sometimes trivial operations. These include allocating memory,
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| 225 | searching directories, reading and writing files, string handling, pattern
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| 226 | matching, arithmetic and many other tasks. Instead of obliging each program to
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| 227 | reinvent the wheel, the GNU system provides all these basic functions in
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| 228 | ready-made libraries. The major library on any Linux system is
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| 229 | <emphasis>Glibc</emphasis>.</para>
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| 230 |
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| 231 | <para>There are two primary ways of linking the functions from a library to a
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| 232 | program that uses them: statically or dynamically. When a program is linked
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| 233 | statically, the code of the used functions is included in the executable,
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| 234 | resulting in a rather bulky program. When a program is dynamically linked, what
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| 235 | is included is a reference to the dynamic linker, the name of the library, and
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| 236 | the name of the function, resulting in a much smaller executable. (A third way
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| 237 | is to use the programming interface of the dynamic linker. See the
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| 238 | <emphasis>dlopen</emphasis> man page for more information.)</para>
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| 239 |
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| 240 | <para>Dynamic linking is the default on Linux and has three major advantages
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| 241 | over static linking. First, you need only one copy of the executable library
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| 242 | code on your hard disk, instead of having many copies of the same code included
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| 243 | into a whole bunch of programs -- thus saving disk space. Second, when several
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| 244 | programs use the same library function at the same time, only one copy of the
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| 245 | function's code is required in core -- thus saving memory space. Third, when a
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| 246 | library function gets a bug fixed or is otherwise improved, you only need to
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| 247 | recompile this one library, instead of having to recompile all the programs that
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| 248 | make use of the improved function.</para>
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| 249 |
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| 250 | <para>If dynamic linking has several advantages, why then do we statically link
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| 251 | the first two packages in this chapter? The reasons are threefold: historical,
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| 252 | educational, and technical. Historical, because earlier versions of LFS
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| 253 | statically linked every program in this chapter. Educational, because knowing
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| 254 | the difference is useful. Technical, because we gain an element of independence
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| 255 | from the host in doing so, meaning that those programs can be used
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| 256 | independently of the host system. However, it's worth noting that an overall
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| 257 | successful LFS build can still be achieved when the first two packages are
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| 258 | built dynamically.</para>
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| 259 |
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| 260 | </sect2>
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| 261 |
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| 262 | </sect1>
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| 263 |
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| 264 |
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[3be4d97] | 265 | <sect1 id="ch-tools-creatingtoolsdir">
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[cfabeed] | 266 | <title>Creating the $LFS/tools directory</title>
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| 267 | <?dbhtml filename="creatingtoolsdir.html" dir="chapter05"?>
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| 268 |
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| 269 | <para>All programs compiled in this chapter will be installed under <filename
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| 270 | class="directory">$LFS/tools</filename> to keep them separate from the
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| 271 | programs compiled in the next chapter. The programs compiled here are only
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| 272 | temporary tools and won't be a part of the final LFS system and by keeping them
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| 273 | in a separate directory, we can later easily throw them away.</para>
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| 274 |
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[f4993cf] | 275 | <para>Later on you might wish to search through the binaries of your system to
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| 276 | see what files they make use of or link against. To make this searching easier
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| 277 | you may want to choose a unique name for the directory in which the temporary
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| 278 | tools are stored. Instead of the simple "tools" you could use something like
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| 279 | "tools-for-lfs". However, you'll need to be careful to adjust all references to
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| 280 | "tools" throughout the book -- including those in any patches, notably the
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| 281 | GCC Specs Patch.</para>
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[cfabeed] | 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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[90e3cb3] | 293 | <note><para>The above command is correct. The <command>ln</command> command
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[f4993cf] | 294 | has a few syntactic variations, so be sure to check the info page before
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| 295 | reporting what you may think is an error.</para></note>
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| 296 |
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| 297 | <para>The created symlink enables us to compile our toolchain so that it always
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[cfabeed] | 298 | refers to <filename>/tools</filename>, meaning that the compiler, assembler
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| 299 | and linker will work both in this chapter (when we are still using some tools
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| 300 | from the host) <emphasis>and</emphasis> in the next (when we are chrooted to
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| 301 | the LFS partition).</para>
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| 302 |
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| 303 | </sect1>
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| 304 |
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| 305 |
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[3be4d97] | 306 | <sect1 id="ch-tools-addinguser">
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[cfabeed] | 307 | <title>Adding the user lfs</title>
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| 308 | <?dbhtml filename="addinguser.html" dir="chapter05"?>
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| 309 |
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| 310 | <para>When logged in as <emphasis>root</emphasis>, making a single mistake
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| 311 | can damage or even wreck your system. Therefore we recommend that you
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| 312 | build the packages in this chapter as an unprivileged user. You could
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[17476c5] | 313 | of course use your own user name, but to make it easier to set up a clean
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[cfabeed] | 314 | work environment we'll create a new user <emphasis>lfs</emphasis> and
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| 315 | use this one during the installation process. As <emphasis>root</emphasis>,
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[c288d97] | 316 | issue the following command to add the new user:</para>
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[cfabeed] | 317 |
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[c288d97] | 318 | <screen><userinput>useradd -s /bin/bash -m -k /dev/null lfs</userinput></screen>
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[cfabeed] | 319 |
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[69276a94] | 320 | <para>The meaning of the switches:</para>
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| 321 |
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| 322 | <itemizedlist>
|
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| 323 | <listitem><para><userinput>-s /bin/bash</userinput>: This makes
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| 324 | <userinput>bash</userinput> the default shell for user
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| 325 | <emphasis>lfs</emphasis>.</para></listitem>
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| 326 |
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| 327 | <listitem><para><userinput>-m -k /dev/null</userinput>: These create a home
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| 328 | directory for <emphasis>lfs</emphasis>, while preventing the files from a
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| 329 | possible <filename>/etc/skel</filename> being copied into it.</para></listitem>
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| 330 | </itemizedlist>
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| 331 |
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[c288d97] | 332 | <para>If you want to be able to log in as <emphasis>lfs</emphasis>, then give
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| 333 | this new user a password:</para>
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| 334 |
|
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| 335 | <screen><userinput>passwd lfs</userinput></screen>
|
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| 336 |
|
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[cfabeed] | 337 | <para>Now grant this new user <emphasis>lfs</emphasis> full access to
|
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| 338 | <filename class="directory">$LFS/tools</filename> by giving it ownership
|
---|
| 339 | of the directory:</para>
|
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| 340 |
|
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| 341 | <screen><userinput>chown lfs $LFS/tools</userinput></screen>
|
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| 342 |
|
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| 343 | <para>If you made a separate working directory as suggested, give user
|
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| 344 | <emphasis>lfs</emphasis> ownership of this directory too:</para>
|
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| 345 |
|
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| 346 | <screen><userinput>chown lfs $LFS/sources</userinput></screen>
|
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| 347 |
|
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| 348 | <para>Next, login as user <emphasis>lfs</emphasis>. This can be done via a
|
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| 349 | virtual console, through a display manager, or with the following substitute
|
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| 350 | user command:</para>
|
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| 351 |
|
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| 352 | <screen><userinput>su - lfs</userinput></screen>
|
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| 353 |
|
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[90e3cb3] | 354 | <para>The "<command>-</command>" instructs <command>su</command> to start a
|
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| 355 | <emphasis>login</emphasis> shell.</para>
|
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[cfabeed] | 356 |
|
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| 357 | </sect1>
|
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| 358 |
|
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| 359 |
|
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[3be4d97] | 360 | <sect1 id="ch-tools-settingenviron">
|
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[cfabeed] | 361 | <title>Setting up the environment</title>
|
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| 362 | <?dbhtml filename="settingenvironment.html" dir="chapter05"?>
|
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| 363 |
|
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[538aa7a] | 364 | <para>We're going to set up a good working environment by creating two new
|
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[90e3cb3] | 365 | startup files for the <command>bash</command> shell. While logged in as
|
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[f4993cf] | 366 | user <emphasis>lfs</emphasis>, issue the following command to create a new
|
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[538aa7a] | 367 | <filename>.bash_profile</filename>:</para>
|
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[cfabeed] | 368 |
|
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| 369 | <screen><userinput>cat > ~/.bash_profile << "EOF"</userinput>
|
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[07ecae2] | 370 | exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
|
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[538aa7a] | 371 | <userinput>EOF</userinput></screen>
|
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| 372 |
|
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[f4993cf] | 373 | <para>Normally, when you log on as user <emphasis>lfs</emphasis>,
|
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| 374 | the initial shell is a <emphasis>login</emphasis> shell which reads the
|
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| 375 | <filename>/etc/profile</filename> of your host (probably containing some
|
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| 376 | settings of environment variables) and then <filename>.bash_profile</filename>.
|
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[90e3cb3] | 377 | The <command>exec env -i ... /bin/bash</command> command in the latter file
|
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[f4993cf] | 378 | replaces the running shell with a new one with a completely empty environment,
|
---|
| 379 | except for the HOME, TERM and PS1 variables. This ensures that no unwanted and
|
---|
| 380 | potentially hazardous environment variables from the host system leak into our
|
---|
| 381 | build environment. The technique used here is a little strange, but it achieves
|
---|
| 382 | the goal of enforcing a clean environment.</para>
|
---|
| 383 |
|
---|
| 384 | <para>The new instance of the shell is a <emphasis>non-login</emphasis> shell,
|
---|
| 385 | which doesn't read the <filename>/etc/profile</filename> or
|
---|
| 386 | <filename>.bash_profile</filename> files, but reads the
|
---|
| 387 | <filename>.bashrc</filename> file instead. Create this latter file now:</para>
|
---|
[538aa7a] | 388 |
|
---|
| 389 | <screen><userinput>cat > ~/.bashrc << "EOF"</userinput>
|
---|
[cfabeed] | 390 | set +h
|
---|
| 391 | umask 022
|
---|
| 392 | LFS=/mnt/lfs
|
---|
| 393 | LC_ALL=POSIX
|
---|
[538aa7a] | 394 | PATH=/tools/bin:/bin:/usr/bin
|
---|
[cfabeed] | 395 | export LFS LC_ALL PATH
|
---|
[538aa7a] | 396 | <userinput>EOF</userinput></screen>
|
---|
[cfabeed] | 397 |
|
---|
[90e3cb3] | 398 | <para>The <command>set +h</command> command turns off
|
---|
| 399 | <command>bash</command>'s hash function. Normally hashing is a useful
|
---|
| 400 | feature: <command>bash</command> uses a hash table to remember the
|
---|
[cfabeed] | 401 | full pathnames of executable files to avoid searching the PATH time and time
|
---|
| 402 | again to find the same executable. However, we'd like the new tools to be
|
---|
[17476c5] | 403 | used as soon as they are installed. By switching off the hash function, our
|
---|
[90e3cb3] | 404 | "interactive" commands (<command>make</command>,
|
---|
| 405 | <command>patch</command>, <command>sed</command>,
|
---|
| 406 | <command>cp</command> and so forth) will always use
|
---|
[cfabeed] | 407 | the newest available version during the build process.</para>
|
---|
| 408 |
|
---|
| 409 | <para>Setting the user file-creation mask to 022 ensures that newly created
|
---|
| 410 | files and directories are only writable for their owner, but readable and
|
---|
| 411 | executable for anyone.</para>
|
---|
[07ecae2] | 412 |
|
---|
[cfabeed] | 413 | <para>The LFS variable should of course be set to the mount point you
|
---|
| 414 | chose.</para>
|
---|
| 415 |
|
---|
| 416 | <para>The LC_ALL variable controls the localization of certain programs,
|
---|
| 417 | making their messages follow the conventions of a specified country. If your
|
---|
| 418 | host system uses a version of Glibc older than 2.2.4,
|
---|
| 419 | having LC_ALL set to something other than "POSIX" or "C" during this chapter
|
---|
| 420 | may cause trouble if you exit the chroot environment and wish to return later.
|
---|
[17476c5] | 421 | By setting LC_ALL to "POSIX" (or "C", the two are equivalent) we ensure that
|
---|
[cfabeed] | 422 | everything will work as expected in the chroot environment.</para>
|
---|
| 423 |
|
---|
| 424 | <para>We prepend <filename>/tools/bin</filename> to the standard PATH so
|
---|
| 425 | that, as we move along through this chapter, the tools we build will get used
|
---|
| 426 | during the rest of the building process.</para>
|
---|
| 427 |
|
---|
[f4993cf] | 428 | <para>Finally, to have our environment fully prepared for building the
|
---|
| 429 | temporary tools, source the just-created profile:</para>
|
---|
[cfabeed] | 430 |
|
---|
[538aa7a] | 431 | <screen><userinput>source ~/.bash_profile</userinput></screen>
|
---|
| 432 |
|
---|
[cfabeed] | 433 | </sect1>
|
---|
| 434 |
|
---|
| 435 |
|
---|
[bc82645e] | 436 | &c5-binutils-pass1;
|
---|
| 437 | &c5-gcc-pass1;
|
---|
| 438 | &c5-kernelheaders;
|
---|
[37ad07a] | 439 | &c5-glibc;
|
---|
[cfabeed] | 440 |
|
---|
| 441 |
|
---|
[3be4d97] | 442 | <sect1 id="ch-tools-locking-glibc">
|
---|
[cfabeed] | 443 | <title>"Locking in" Glibc</title>
|
---|
| 444 | <?dbhtml filename="lockingglibc.html" dir="chapter05"?>
|
---|
| 445 |
|
---|
| 446 | <para>Now that the temporary C libraries have been installed, we want all
|
---|
| 447 | the tools compiled in the rest of this chapter to be linked against these
|
---|
| 448 | libraries. To accomplish this, we need to adjust the linker and the compiler's
|
---|
| 449 | specs file.</para>
|
---|
| 450 |
|
---|
| 451 | <para>First install the adjusted linker by running the following from within
|
---|
| 452 | the <filename class="directory">binutils-build</filename> directory:</para>
|
---|
| 453 |
|
---|
| 454 | <screen><userinput>make -C ld install</userinput></screen>
|
---|
| 455 |
|
---|
| 456 | <para>The linker was adjusted a little while back, at the end of the first
|
---|
| 457 | pass of Binutils. From this point onwards everything will link <emphasis>only
|
---|
| 458 | </emphasis> against the libraries in <filename>/tools/lib</filename>.</para>
|
---|
| 459 |
|
---|
| 460 | <note><para>If you somehow missed the earlier warning to retain the Binutils
|
---|
| 461 | source and build directories from the first pass or otherwise accidentally
|
---|
| 462 | deleted them or just don't have access to them, don't worry, all is not lost.
|
---|
[f4993cf] | 463 | Just ignore the above command. The result is a small chance of the subsequent
|
---|
| 464 | testing programs linking against libraries on the host. This is not ideal, but
|
---|
[cfabeed] | 465 | it's not a major problem. The situation is corrected when we install the
|
---|
[f4993cf] | 466 | second pass of Binutils a bit further on.</para></note>
|
---|
[cfabeed] | 467 |
|
---|
| 468 | <para>Now that the adjusted linker is installed, you have to remove the
|
---|
| 469 | Binutils build and source directories.</para>
|
---|
| 470 |
|
---|
| 471 | <para>The next thing to do is to amend our GCC specs file so that it points
|
---|
| 472 | to the new dynamic linker. A simple sed will accomplish this:</para>
|
---|
| 473 |
|
---|
| 474 | <!-- Ampersands are needed to allow cut and paste -->
|
---|
[17476c5] | 475 |
|
---|
[cfabeed] | 476 | <screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
|
---|
| 477 | sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \
|
---|
| 478 | $SPECFILE > tempspecfile &&
|
---|
| 479 | mv -f tempspecfile $SPECFILE &&
|
---|
| 480 | unset SPECFILE</userinput></screen>
|
---|
| 481 |
|
---|
| 482 | <para>We recommend that you cut-and-paste the above rather than try and type it
|
---|
[51fe215] | 483 | all in. Or you can edit the specs file by hand if you want to: just replace the
|
---|
| 484 | occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2". Be sure to
|
---|
| 485 | visually inspect the specs file to verify the intended change was actually
|
---|
| 486 | made.</para>
|
---|
[cfabeed] | 487 |
|
---|
| 488 | <important><para>If you are working on a platform where the name of the dynamic
|
---|
| 489 | linker is something other than <filename>ld-linux.so.2</filename>, you
|
---|
| 490 | <emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
|
---|
| 491 | name of your platform's dynamic linker in the above commands. Refer back to
|
---|
[3be4d97] | 492 | <xref linkend="ch-tools-toolchaintechnotes"/> if necessary.</para></important>
|
---|
[cfabeed] | 493 |
|
---|
| 494 | <para>Lastly, there is a possibility that some include files from the host
|
---|
| 495 | system have found their way into GCC's private include dir. This can happen
|
---|
| 496 | because of GCC's "fixincludes" process which runs as part of the GCC build.
|
---|
[17476c5] | 497 | We'll explain more about this further on in this chapter. For now, run the
|
---|
[cfabeed] | 498 | following commands to eliminate this possibility:</para>
|
---|
| 499 |
|
---|
| 500 | <screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>
|
---|
| 501 |
|
---|
| 502 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
| 503 | <literallayout></literallayout>
|
---|
| 504 |
|
---|
| 505 | <caution><para>It is imperative at this point to stop and ensure that the basic
|
---|
| 506 | functions (compiling and linking) of the new toolchain are working as expected.
|
---|
| 507 | For this we are going to perform a simple sanity check:</para>
|
---|
| 508 |
|
---|
| 509 | <screen><userinput>echo 'main(){}' > dummy.c
|
---|
[51fe215] | 510 | cc dummy.c
|
---|
[cfabeed] | 511 | readelf -l a.out | grep ': /tools'</userinput></screen>
|
---|
| 512 |
|
---|
| 513 | <para>If everything is working correctly, there should be no errors, and the
|
---|
| 514 | output of the last command will be:</para>
|
---|
| 515 |
|
---|
| 516 | <blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
|
---|
| 517 |
|
---|
[51fe215] | 518 | <para>(Of course allowing for platform specific differences in dynamic linker
|
---|
| 519 | name). Note especially that <filename class="directory">/tools/lib</filename>
|
---|
| 520 | appears as the prefix of our dynamic linker. If you did not receive the output
|
---|
| 521 | as shown above, or received no output at all, then something is seriously wrong.
|
---|
| 522 | You will need to investigate and retrace your steps to find out where the
|
---|
| 523 | problem is and correct it. There is no point in continuing until this is done.
|
---|
[90e3cb3] | 524 | First, redo the sanity check using <command>gcc</command> instead of
|
---|
| 525 | <command>cc</command>. If this works it means the
|
---|
[51fe215] | 526 | <filename class="symlink">/tools/bin/cc</filename> symlink is missing. Revisit
|
---|
[3be4d97] | 527 | <xref linkend="ch-tools-gcc-pass1"/> and fix the symlink. Second, ensure your $PATH
|
---|
[51fe215] | 528 | is correct. You can check this by running <userinput>echo $PATH</userinput> and
|
---|
| 529 | verifying that <filename class="directory">/tools/bin</filename> is at the head
|
---|
| 530 | of the list. If the $PATH is wrong it could mean you're not logged in as user
|
---|
| 531 | <emphasis>lfs</emphasis> or something went wrong back in
|
---|
[3be4d97] | 532 | <xref linkend="ch-tools-settingenviron"/>. Third, something may have gone wrong with
|
---|
[51fe215] | 533 | the specs file amendment above. In this case redo the specs file amendment
|
---|
| 534 | ensuring to cut-and-paste the commands as was recommended.</para>
|
---|
[cfabeed] | 535 |
|
---|
| 536 | <para>Once you are satisfied that all is well, clean up the test files:</para>
|
---|
| 537 |
|
---|
| 538 | <screen><userinput>rm dummy.c a.out</userinput></screen>
|
---|
| 539 | </caution>
|
---|
| 540 |
|
---|
| 541 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
| 542 | <literallayout></literallayout>
|
---|
| 543 |
|
---|
| 544 | <para>This completes the installation of the self-contained toolchain, and it
|
---|
| 545 | can now be used to build the rest of the temporary tools.</para>
|
---|
| 546 |
|
---|
| 547 | </sect1>
|
---|
| 548 |
|
---|
| 549 |
|
---|
[37ad07a] | 550 | &c5-tcl;
|
---|
| 551 | &c5-expect;
|
---|
| 552 | &c5-dejagnu;
|
---|
[bc82645e] | 553 | &c5-gcc-pass2;
|
---|
| 554 | &c5-binutils-pass2;
|
---|
[cfabeed] | 555 |
|
---|
[bc82645e] | 556 | &c5-gawk;
|
---|
| 557 | &c5-coreutils;
|
---|
[abbd27a5] | 558 | &c5-bzip2;
|
---|
[bc82645e] | 559 | &c5-gzip;
|
---|
[abbd27a5] | 560 | &c5-diffutils;
|
---|
[5e2cb65] | 561 | &c5-findutils;
|
---|
[abbd27a5] | 562 | &c5-make;
|
---|
[bc82645e] | 563 | &c5-grep;
|
---|
[abbd27a5] | 564 | &c5-sed;
|
---|
[bc82645e] | 565 | &c5-gettext;
|
---|
| 566 | &c5-ncurses;
|
---|
| 567 | &c5-patch;
|
---|
[abbd27a5] | 568 | &c5-tar;
|
---|
| 569 | &c5-texinfo;
|
---|
[bc82645e] | 570 | &c5-bash;
|
---|
[5e2cb65] | 571 | &c5-utillinux;
|
---|
[bc82645e] | 572 | &c5-perl;
|
---|
[6370fa6] | 573 |
|
---|
[503e1a6] | 574 |
|
---|
[3be4d97] | 575 | <sect1 id="ch-tools-stripping">
|
---|
[69a52c1] | 576 | <title>Stripping</title>
|
---|
| 577 | <?dbhtml filename="stripping.html" dir="chapter05"?>
|
---|
| 578 |
|
---|
[1cb7ced] | 579 | <para>The steps in this section are optional. If your LFS partition is rather
|
---|
| 580 | small, you will be glad to learn that you can throw away some unnecessary
|
---|
| 581 | things. The executables and libraries you have built so far contain about 130 MB
|
---|
| 582 | of unneeded debugging symbols. Remove those symbols like this:</para>
|
---|
[69a52c1] | 583 |
|
---|
[21ba4e3] | 584 | <screen><userinput>strip --strip-unneeded /tools/{,s}bin/*
|
---|
| 585 | strip --strip-debug /tools/lib/*</userinput></screen>
|
---|
[69a52c1] | 586 |
|
---|
| 587 | <para>The first of the above commands will skip some twenty files, reporting
|
---|
| 588 | that it doesn't recognize their file format. Most of them are scripts instead
|
---|
| 589 | of binaries.</para>
|
---|
| 590 |
|
---|
| 591 | <para>Take care <emphasis>not</emphasis> to use
|
---|
[90e3cb3] | 592 | <emphasis>--strip-unneeded</emphasis> on the libraries -- they would be
|
---|
[69a52c1] | 593 | destroyed and you would have to build Glibc all over again.</para>
|
---|
| 594 |
|
---|
[238527e] | 595 | <para>To save another couple of megabytes, you can throw away all the
|
---|
| 596 | documentation:</para>
|
---|
[69a52c1] | 597 |
|
---|
[21ba4e3] | 598 | <screen><userinput>rm -rf /tools/{,share/}{doc,info,man}</userinput></screen>
|
---|
[69a52c1] | 599 |
|
---|
[a6505d9] | 600 | <para>You will now need to have at least 850 MB of free space on your LFS
|
---|
[ab3b93b] | 601 | file system to be able to build and install Glibc in the next phase. If you can
|
---|
[1668d8e] | 602 | build and install Glibc, you can build and install the rest too.</para>
|
---|
[69a52c1] | 603 |
|
---|
| 604 | </sect1>
|
---|
| 605 |
|
---|
[6370fa6] | 606 | </chapter>
|
---|
| 607 |
|
---|