source: BOOK/chroot/x86/before-chroot.xml @ 6a24bdf

Last change on this file since 6a24bdf was 6a24bdf, checked in by William Harrington <kb0iic@…>, 9 years ago

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
8<sect1 id="ch-chroot-before-chroot">
9  <?dbhtml filename="before-chroot.html"?>
10  <title>Before Entering the Chroot Environment</title>
12  <sect2 role="determining-ifneeded">
13    <title>Determining if steps need to be taken</title>
15    <para>Before we can enter the chroot we have to make sure that the system is
16    in the proper state. From this point on the <envar>${CLFS_TARGET}</envar>
17    environment variable will no longer exist, so it will have no bearing on the
18    rest of the book - most packages will rely on
19    <command>config.guess</command> provided by
20    <xref linkend="ch-system-automake"/>. Packages that do not use autotools
21    either do not care about the target triplet, or have their own means
22    of determining its value.</para>
24    <para>In both cases, the information about the host cpu used to determine
25    the target triplet is gathered from the same place,
26    <command>uname -m</command>. Executing this command outside of the chroot
27    as well as inside the chroot will have the exact same output.</para>
29   <para>If you're unsure if your host and target have the same target
30    triplet, you can use this test to determine what the host's target triplet
31    is and if you need to take any steps to ensure that you don't build for the
32    wrong architecture. Extract the <xref linkend="ch-system-automake"/> tarball
33    and <command>cd</command> into the created directory. Then execute the
34    following to see what the detected target triplet is by
35    <command>config.guess</command>:</para>
39    <para>If the output of that command does not equal what is in
40    <envar>${CLFS_TARGET}</envar> then you need to read on. If it does then you
41    can safely continue onto <xref linkend="ch-chroot-chroot"/>.</para>
43  </sect2>
45  <sect2 role="using-setarch">
46    <title>Using Setarch</title>
48    <para>If your host has a tool called <command>setarch</command> this may
49    solve your problems. The reason for saying may is because on a architecture
50    such as x86_64, using <command>setarch linux32 uname -m</command> will only
51    ever output i686. It is not possible to get an output of i486 or i586.</para>
53    <para>To test if setarch does everything you need it to, execute the
54    following command from inside the <xref linkend="ch-system-automake"/>
55    directory:</para>
57<screen><userinput>setarch linux32 lib/config.guess</userinput></screen>
59    <para>If the output of the command above equals what is in
60    <envar>${CLFS_TARGET}</envar> then you have a viable solution. You can
61    wrap the chroot command on the next page with
62    <command>setarch linux32</command>. It will look like the following:</para>
64<screen><userinput>setarch linux32 chroot "${CLFS}" /tools/bin/env -i \
65    HOME=/root TERM="${TERM}" PS1='\u:\w\$ ' \
66    PATH=/bin:/usr/bin:/sbin:/usr/sbin:/tools/bin \
67    /tools/bin/bash --login +h</userinput></screen>
69    <para>If setarch works for you then you can safely continue onto
70    <xref linkend="ch-chroot-chroot"/>. If not, there is one more option
71    covered in this book.</para>
73  </sect2>
75  <sect2 role="using-uname_hack">
76    <title>Using a Uname Hack</title>
78    <para os="uua">The Uname Hack is a kernel module that modifies the output of
79    <command>uname -m</command> by directly changing the value of the
80    detected machine type. The kernel module will save the original value
81    and restore it when the module is unloaded.</para>
83    <variablelist os="uub" role="materials">
84      <varlistentry>
85        <term>Uname Hack (&uname_hack-version;) - &uname_hack-size;:</term>
87        <listitem>
88          <para>Home page: <ulink url="&uname_hack-home;"/></para>
89          <para>Download: <ulink url="&uname_hack-url;"/></para>
90          <para>MD5 sum: <literal>&uname_hack-md5;</literal></para>
91        </listitem>
92      </varlistentry>
93    </variablelist>
95    <para os="uuc">Extract the tarball and <command>cd</command> into the
96    created directory. To build the Uname Hack you must have the kernel sources
97    for your currently running kernel available. Build the Uname Hack with the
98    following or similar command:</para>
100<screen os="uud"><userinput>make uname_hack_fake_machine=i486</userinput></screen>
102    <variablelist os="uue">
103      <title>The meaning of the make and install options:</title>
105      <varlistentry os="uue1">
106        <term><parameter>uname_hack_fake_machine=i486</parameter></term>
107        <listitem>
108          <para>This parameter sets the value that the uts machine type will be
109          changed to. Alternatively this could be set to i586 or i686.</para>
110        </listitem>
111      </varlistentry>
113    </variablelist>
115    <para os="uuf">In the top level directory of the Uname Hack package you
116    should see a file named <filename>uname_hack.ko</filename>. As soon as
117    that module is loaded into the running kernel the output of
118    <command>uname -m</command> will be affected immediately system-wide.
119    Load the kernel module with the following command:</para>
121<screen os="uug"><userinput>insmod uname_hack.ko</userinput></screen>
123    <para os="uuh">To test if the Uname Hack is working properly, execute the
124    following command from inside the <xref linkend="ch-system-automake"/>
125    directory:</para>
127<screen os="uui"><userinput>lib/config.guess</userinput></screen>
129    <para os="uuj">The output of the above command should be the same as the
130    <envar>${CLFS_TARGET}</envar> environment variable. If this is not the
131    case, you can try and get help on the CLFS Support Mailing List or the
132    IRC Channel. See <xref linkend="ch-intro-askforhelp"/> for more
133    information.</para>
135  </sect2>
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