source: BOOK/chroot/x86/before-chroot.xml@ 3390ed6

clfs-1.2 clfs-2.1 clfs-3.0.0-systemd clfs-3.0.0-sysvinit systemd sysvinit
Last change on this file since 3390ed6 was 42a32ea, checked in by Joe Ciccone <jciccone@…>, 16 years ago

Add a page right before Entering the Chroot Enviornment. This page covers the problem of building a 32bit system from a 64bit host or building a older 32bit system from another newer 32bit system.

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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 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-chroot-before-chroot">
9 <?dbhtml filename="before-chroot.html"?>
10 <title>Before Entering the Chroot Environment</title>
11
12 <sect2 role="determining-ifneeded">
13 <title>Determining if steps need to be taken</title>
14
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>${CLFS_TARGET}</envar>
17 enviornment variable will no longer exist, so it will have no bearing on the
18 rest of the book. From this point on, most packages will rely on
19 <command>config.guess</command> provided by
20 <xref linkend="ch-system-automake"/>. Packages that do not use autotools
21 either do not care about the target triplet, or they have their own means
22 of determining it's value.</para>
23
24 <para>In both cases, The information about the host cpu used to determine
25 the target triplet is gathered from the same place,
26 <command>uname -m</command>. Executing this command outside of the chroot
27 aswell as inside the chroot will have the exact same output.</para>
28
29 <para>If you're unsure if you're host and target have the same target
30 triplet, you can use this test to determine what the hosts target triplet
31 is and if you need to take any steps to ensure that you don't build for the
32 wrong architecture. Extract the <xref linkend="ch-system-automake"/> tarball
33 and <command>cd</command> into the created directory. Then execute the
34 following to see what they detected target triplet is by
35 <command>config.guess</command>.</para>
36
37<screen><userinput>lib/config.guess</userinput></screen>
38
39 <para>If the output of that command does not equal what is in
40 <envar>${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>
42
43 </sect2>
44
45 <sect2 role="using-setarch">
46 <title>Using Setarch</title>
47
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>
52
53 <para>To test if setarch does everything you need it to, execute the
54 following command from inside of the <xref linkend="ch-system-automake"/>
55 directory:</para>
56
57<screen><userinput>setarch linux32 lib/config.guess</userinput></screen>
58
59 <para>If the output of the command above equals what is in
60 <envar>${CLFS_TARGET}</envar> then you have a viable solution. You can
61 wrap the chroot command on the next page with
62 <command>setarch linux32</command>. It will look like the following:</para>
63
64<screen><userinput>setarch linux32 chroot "${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>
68
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>
72
73 </sect2>
74
75 <sect2 role="using-uname_hack">
76 <title>Using a Uname Hack</title>
77
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>
82
83 <variablelist os="uub" role="materials">
84 <varlistentry>
85 <term>Uname Hack (&uname_hack-version;) - &uname_hack-size;:</term>
86
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>
94
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 you currently running kernel available. Build the Uname Hack with the
98 following or similar command:</para>
99
100<screen os="uud"><userinput>make uname_hack_fake_machine=i486</userinput></screen>
101
102 <para os="uue">In the top level directory of the Uname Hack pacakage you
103 should see a file named uname_hack.ko. As soon as that module is loaded
104 into the running kernel the output of <command>uname -m</command> will be
105 affected immediately system-wide. Load the kernel module with the following
106 command:</para>
107
108<screen os="uuf"><userinput>insmod uname_hack.ko</userinput></screen>
109
110 <para os="uug">To test if the Uname Hack is working properly, execute the
111 following command from inside of the <xref linkend="ch-system-automake"/>
112 directory:</para>
113
114<screen os="uuh"><userinput>lib/config.guess</userinput></screen>
115
116 <para os="uui">The output of the above command should be the same as the
117 <envar>${CLFS_TARGET}</envar> enviornment variable. If this is not the
118 case, You can try and get help on the CLFS Support Mailing List or the
119 IRC Channel. See <xref linkend="ch-intro-askforhelp"/> for more
120 information.</para>
121
122 </sect2>
123
124</sect1>
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