Set up a good working environment by creating two new startup
files for the bash shell. While logged in as user
clfs
, issue the following
command to create a new .bash_profile
:
cat > ~/.bash_profile << "EOF"
exec env -i HOME=${HOME} TERM=${TERM} PS1='\u:\w\$ ' /bin/bash
EOF
When logged on as user clfs
,
the initial shell is usually a login shell which
reads the /etc/profile
of the host (probably
containing some settings and environment variables) and then
.bash_profile
. The
exec env -i.../bin/bash command in the
.bash_profile
file replaces the running shell with
a new one with a completely empty environment, except for the
HOME
, TERM
, and PS1
variables.
This ensures that no unwanted and potentially hazardous environment
variables from the host system leak into the build environment. The
technique used here achieves the goal of ensuring a clean environment.
The new instance of the shell is a non-login
shell, which does not read the /etc/profile
or
.bash_profile
files, but rather reads the
.bashrc
file instead. Create the
.bashrc
file now:
cat > ~/.bashrc << "EOF"
set +h
umask 022
CLFS=/mnt/clfs
LC_ALL=POSIX
PATH=/cross-tools/bin:/bin:/usr/bin
export CLFS LC_ALL PATH
EOF
The set +h command turns off
bash's hash function. Hashing is ordinarily a useful
feature—bash uses a hash table to remember the
full path of executable files to avoid searching the PATH
time and again to find the same executable. However, the new tools should
be used as soon as they are installed. By switching off the hash function,
the shell will always search the PATH
when a program is to
be run. As such, the shell will find the newly compiled tools in
/cross-tools
as soon as they are
available without remembering a previous version of the same program in a
different location.
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 open(2) system call, new files will end up with permission mode 644 and directories with mode 755).
The CLFS
variable should be set to the
chosen mount point.
The LC_ALL
variable controls the localization
of certain programs, making their messages follow the conventions of a
specified country. If the host system uses a version of Glibc older
than 2.2.4, having LC_ALL
set to something other than
“POSIX” or “C” (during this chapter) may cause
issues if you exit the chroot environment and wish to return later.
Setting LC_ALL
to “POSIX” or “C”
(the two are equivalent) ensures that everything will work as expected in
the chroot environment.
By putting /cross-tools/bin
at the beginning of the PATH
, the cross-compiler
built in Constructing Cross-Compile Tools will be picked up by
the build process for the temp-system packages before anything that
may be installed on the host. This, combined with turning off
hashing, helps to ensure that you will be using the cross-compile
tools to build the temp-system in /tools.
Finally, to have the environment fully prepared for building the temporary tools, source the just-created user profile:
source ~/.bash_profile