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Setting Up the Environment
Set up a good working environment by creating two new startup files for the <command>bash</command> shell. While logged in as user <systemitem class="username">lfs</systemitem>, issue the following command to create a new <filename>.bash_profile</filename>:
<userinput>cat &gt; ~/.bash_profile &lt;&lt; "EOF"
<literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal>
EOF</userinput>
When logged on as user <systemitem class="username">lfs</systemitem>, or when switched to the &lfs-user; user using an <command>su</command> command with the <quote><parameter>-</parameter></quote> option, the initial shell is a <emphasis>login</emphasis> shell which reads the <filename>/etc/profile</filename> of the host (probably containing some settings and environment variables) and then <filename>.bash_profile</filename>. The <command>exec env -i.../bin/bash</command> command in the <filename>.bash_profile</filename> file replaces the running shell with a new one with a completely empty environment, except for the <envar>HOME</envar>, <envar>TERM</envar>, and <envar>PS1</envar> variables. This ensures that no unwanted and potentially hazardous environment variables from the host system leak into the build environment.
The new instance of the shell is a <emphasis>non-login</emphasis> shell, which does not read, and execute, the contents of the <filename>/etc/profile</filename> or <filename>.bash_profile</filename> files, but rather reads, and executes, the <filename>.bashrc</filename> file instead. Create the <filename>.bashrc</filename> file now:
<userinput>cat &gt; ~/.bashrc &lt;&lt; "EOF"
<literal>set +h
umask 022
LFS=/mnt/lfs
LC_ALL=POSIX
LFS_TGT=$(uname -m)-lfs-linux-gnu
PATH=/usr/bin
if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
PATH=$LFS/tools/bin:$PATH
CONFIG_SITE=$LFS/usr/share/config.site
export LFS LC_ALL LFS_TGT PATH CONFIG_SITE</literal>
EOF</userinput>
The meaning of the settings in <filename>.bashrc</filename>
<parameter>set +h</parameter>
The <command>set +h</command> command turns off <command>bash</command>'s hash function. Hashing is ordinarily a useful feature&mdash;<command>bash</command> uses a hash table to remember the full path to executable files to avoid searching the <envar>PATH</envar> time and again to find the same executable. However, the new tools should be used as soon as they are installed. Switching off the hash function forces the shell to search the <envar>PATH</envar> whenever a program is to be run. As such, the shell will find the newly compiled tools in <filename class="directory">$LFS/tools/bin</filename> as soon as they are available without remembering a previous version of the same program provided by the host distro, in <filename class='directory'>/usr/bin</filename> or <filename class='directory'>/bin</filename>.
<parameter>umask 022</parameter>
Setting the user file-creation mask (umask) to 022 ensures that newly created files and directories are only writable by their owner, but are readable and executable by anyone (assuming default modes are used by the <ulink role='man' url='&man;open.2'>open(2)</ulink> system call, new files will end up with permission mode 644 and directories with mode 755).
<parameter>LFS=/mnt/lfs</parameter>
The <envar>LFS</envar> variable should be set to the chosen mount point.
<parameter>LC_ALL=POSIX</parameter>
The <envar>LC_ALL</envar> variable controls the localization of certain programs, making their messages follow the conventions of a specified country. Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote> (the two are equivalent) ensures that everything will work as expected in the cross-compilation environment.
<parameter>LFS_TGT=$(uname -m)-lfs-linux-gnu</parameter>
The <envar>LFS_TGT</envar> variable sets a non-default, but compatible machine description for use when building our cross-compiler and linker and when cross-compiling our temporary toolchain. More information is provided by <xref linkend="ch-tools-toolchaintechnotes" role=""/>.
<parameter>PATH=/usr/bin</parameter>
Many modern Linux distributions have merged <filename class="directory">/bin</filename> and <filename class="directory">/usr/bin</filename>. When this is the case, the standard <envar>PATH</envar> variable should be set to <filename class="directory">/usr/bin/</filename> for the <xref linkend="chapter-temporary-tools"/> environment. When this is not the case, the following line adds <filename class="directory">/bin</filename> to the path.
<parameter>if [ ! -L /bin ]; then PATH=/bin:$PATH; fi</parameter>
If <filename class="directory">/bin</filename> is not a symbolic link, it must be added to the <envar>PATH</envar> variable.

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  1. Linux From Scratch
  2. chapter04_settingenviron
  3. English
<userinput>cat &gt; ~/.bashrc &lt;&lt; "EOF"
<literal>set +h
umask 022
LFS=/mnt/lfs
LC_ALL=POSIX
LFS_TGT=$(uname -m)-lfs-linux-gnu
PATH=/usr/bin
if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
PATH=$LFS/tools/bin:$PATH
CONFIG_SITE=$LFS/usr/share/config.site
export LFS LC_ALL LFS_TGT PATH CONFIG_SITE</literal>
EOF</userinput>
a year ago
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Source string description
type: Content of: <sect1><screen>
Flags
ignore-same, no-wrap, read-only, xml-text
Source string location
lfs-en/chapter04/settingenviron.xml:41
String age
a year ago
Last updated
8 months ago
Source string age
a year ago
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