1 | <?xml version="1.0" encoding="ISO-8859-1"?> |
---|
2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" |
---|
3 | "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [ |
---|
4 | <!ENTITY % general-entities SYSTEM "../general.ent"> |
---|
5 | %general-entities; |
---|
6 | ]> |
---|
7 | |
---|
8 | <sect1 id="ch-final-preps-settingenviron"> |
---|
9 | <?dbhtml filename="settingenvironment.html"?> |
---|
10 | |
---|
11 | <title>Setting Up the Environment</title> |
---|
12 | |
---|
13 | <para os="a">Set up a good working environment by creating two new startup |
---|
14 | files for the <command>bash</command> shell. While logged in as user |
---|
15 | <systemitem class="username">lfs</systemitem>, issue the following |
---|
16 | command to create a new <filename>.bash_profile</filename>:</para> |
---|
17 | |
---|
18 | <screen os="b"><userinput>cat > ~/.bash_profile << "EOF" |
---|
19 | <literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal> |
---|
20 | EOF</userinput></screen> |
---|
21 | |
---|
22 | <para os="c">When logged on as user <systemitem class="username">lfs</systemitem>, |
---|
23 | the initial shell is usually a <emphasis>login</emphasis> shell which |
---|
24 | reads the <filename>/etc/profile</filename> of the host (probably |
---|
25 | containing some settings and environment variables) and then |
---|
26 | <filename>.bash_profile</filename>. The |
---|
27 | <command>exec env -i.../bin/bash</command> command in the |
---|
28 | <filename>.bash_profile</filename> file replaces the running shell with |
---|
29 | a new one with a completely empty environment, except for the |
---|
30 | <envar>HOME</envar>, <envar>TERM</envar>, and <envar>PS1</envar> variables. |
---|
31 | This ensures that no unwanted and potentially hazardous environment |
---|
32 | variables from the host system leak into the build environment. The |
---|
33 | technique used here achieves the goal of ensuring a clean environment.</para> |
---|
34 | |
---|
35 | <para os="d">The new instance of the shell is a <emphasis>non-login</emphasis> |
---|
36 | shell, which does not read the <filename>/etc/profile</filename> or |
---|
37 | <filename>.bash_profile</filename> files, but rather reads the |
---|
38 | <filename>.bashrc</filename> file instead. Create the |
---|
39 | <filename>.bashrc</filename> file now:</para> |
---|
40 | |
---|
41 | <screen os="e"><userinput>cat > ~/.bashrc << "EOF" |
---|
42 | <literal>set +h |
---|
43 | umask 022 |
---|
44 | LFS=/mnt/lfs |
---|
45 | LC_ALL=POSIX |
---|
46 | PATH=/cross-tools/bin:/bin:/usr/bin |
---|
47 | export LFS LC_ALL PATH</literal> |
---|
48 | EOF</userinput></screen> |
---|
49 | |
---|
50 | <para os="f">The <command>set +h</command> command turns off |
---|
51 | <command>bash</command>'s hash function. Hashing is ordinarily a useful |
---|
52 | feature—<command>bash</command> uses a hash table to remember the |
---|
53 | full path of executable files to avoid searching the <envar>PATH</envar> |
---|
54 | time and again to find the same executable. However, the new tools should |
---|
55 | be used as soon as they are installed. By switching off the hash function, |
---|
56 | the shell will always search the <envar>PATH</envar> when a program is to |
---|
57 | be run. As such, the shell will find the newly compiled tools in |
---|
58 | <filename class="directory">$LFS/cross-tools</filename> as soon as they are |
---|
59 | available without remembering a previous version of the same program in a |
---|
60 | different location.</para> |
---|
61 | |
---|
62 | <para os="g">Setting the user file-creation mask (umask) to 022 ensures that |
---|
63 | newly created files and directories are only writable by their owner, |
---|
64 | but are readable and executable by anyone (assuming default modes are |
---|
65 | used by the open(2) system call, new files will end up with permission |
---|
66 | mode 644 and directories with mode 755).</para> |
---|
67 | |
---|
68 | <para os="h">The <envar>LFS</envar> variable should be set to the |
---|
69 | chosen mount point.</para> |
---|
70 | |
---|
71 | <para os="i">TO BE REWRITTEN - The <envar>LC_ALL</envar> variable controls |
---|
72 | the localization of |
---|
73 | certain programs, making their messages follow the conventions of a |
---|
74 | specified country. If the host system uses a version of Glibc older |
---|
75 | than 2.2.4, having <envar>LC_ALL</envar> set to something other than |
---|
76 | <quote>POSIX</quote> or <quote>C</quote> (during this chapter) may cause |
---|
77 | issues if you exit the chroot environment and wish to return later. |
---|
78 | Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote> |
---|
79 | (the two are equivalent) ensures that everything will work as expected in |
---|
80 | the chroot environment.</para> |
---|
81 | |
---|
82 | <para os="j">By putting <filename class="directory">/cross-tools/bin</filename> ahead |
---|
83 | of the standard <envar>PATH</envar>, all the programs installed in |
---|
84 | <xref linkend="chapter-cross-tools"/> are picked up by the cross-compiler |
---|
85 | immediately after their installation. This, combined with turning off |
---|
86 | hashing, limits the risk that old programs are used from the host when |
---|
87 | building a sane set of cross-compiler tools.</para> |
---|
88 | |
---|
89 | <para os="k">Finally, to have the environment fully prepared for building the |
---|
90 | temporary tools, source the just-created user profile:</para> |
---|
91 | |
---|
92 | <screen os="l"><userinput>source ~/.bash_profile</userinput></screen> |
---|
93 | |
---|
94 | </sect1> |
---|