1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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3 | <!ENTITY % general-entities SYSTEM "../general.ent">
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4 | %general-entities;
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5 | ]>
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6 | <sect1 id="ch-tools-settingenviron">
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7 | <title>Setting up the environment</title>
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8 | <?dbhtml filename="settingenvironment.html"?>
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9 |
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10 | <para>We're going to set up a good working environment by creating two new
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11 | startup files for the <command>bash</command> shell. While logged in as
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12 | user <emphasis>lfs</emphasis>, issue the following command to create a new
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13 | <filename>.bash_profile</filename>:</para>
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14 |
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15 | <screen><userinput>cat > ~/.bash_profile << "EOF"
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16 | exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
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17 | EOF</userinput></screen>
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18 |
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19 | <para>Normally, when you log on as user <emphasis>lfs</emphasis>,
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20 | the initial shell is a <emphasis>login</emphasis> shell which reads the
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21 | <filename>/etc/profile</filename> of your host (probably containing some
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22 | settings of environment variables) and then <filename>.bash_profile</filename>.
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23 | The <command>exec env -i ... /bin/bash</command> command in the latter file
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24 | replaces the running shell with a new one with a completely empty environment,
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25 | except for the HOME, TERM and PS1 variables. This ensures that no unwanted and
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26 | potentially hazardous environment variables from the host system leak into our
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27 | build environment. The technique used here is a little strange, but it achieves
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28 | the goal of enforcing a clean environment.</para>
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29 |
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30 | <para>The new instance of the shell is a <emphasis>non-login</emphasis> shell,
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31 | which doesn't read the <filename>/etc/profile</filename> or
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32 | <filename>.bash_profile</filename> files, but reads the
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33 | <filename>.bashrc</filename> file instead. Create this latter file now:</para>
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34 |
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35 | <screen><userinput>cat > ~/.bashrc << "EOF"
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36 | set +h
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37 | umask 022
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38 | LFS=/mnt/lfs
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39 | LC_ALL=POSIX
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40 | PATH=/tools/bin:/bin:/usr/bin
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41 | export LFS LC_ALL PATH
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42 | EOF</userinput></screen>
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43 |
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44 | <para>The <command>set +h</command> command turns off
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45 | <command>bash</command>'s hash function. Normally hashing is a useful
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46 | feature: <command>bash</command> uses a hash table to remember the
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47 | full pathnames of executable files to avoid searching the PATH time and time
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48 | again to find the same executable. However, we'd like the new tools to be
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49 | used as soon as they are installed. By switching off the hash function, our
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50 | <quote>interactive</quote> commands (<command>make</command>,
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51 | <command>patch</command>, <command>sed</command>,
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52 | <command>cp</command> and so forth) will always use
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53 | the newest available version during the build process.</para>
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54 |
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55 | <para>Setting the user file-creation mask to 022 ensures that newly created
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56 | files and directories are only writable for their owner, but readable and
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57 | executable for anyone.</para>
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58 |
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59 | <para>The LFS variable should of course be set to the mount point you
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60 | chose.</para>
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61 |
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62 | <para>The LC_ALL variable controls the localization of certain programs,
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63 | making their messages follow the conventions of a specified country. If your
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64 | host system uses a version of Glibc older than 2.2.4,
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65 | having LC_ALL set to something other than <quote>POSIX</quote> or
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66 | <quote>C</quote> during this chapter may cause trouble if you exit the chroot
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67 | environment and wish to return later. By setting LC_ALL to <quote>POSIX</quote>
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68 | (or <quote>C</quote>, the two are equivalent) we ensure that
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69 | everything will work as expected in the chroot environment.</para>
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70 |
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71 | <para>We prepend <filename class="directory">/tools/bin</filename> to the standard PATH so
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72 | that, as we move along through this chapter, the tools we build will get used
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73 | during the rest of the building process.</para>
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74 |
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75 | <para>Finally, to have our environment fully prepared for building the
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76 | temporary tools, source the just-created profile:</para>
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77 |
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78 | <screen><userinput>source ~/.bash_profile</userinput></screen>
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79 |
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80 | </sect1>
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