Setting Up the Environment

Set up a good working environment by creating two new startup files for the bash shell. While logged in as user lfs, issue the following command to create a new .bash_profile:

cat > ~/.bash_profile << "EOF"
exec env -i HOME=$HOME TERM=$TERM PS1='($?) (LFS) \u:\w\$ ' /bin/bash
EOF

When logged on as user lfs, or when switched to the lfs user using an su command with the “-” option, the initial shell is 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 new instance of the shell is a non-login shell, which does not read, and execute, the contents of the /etc/profile or .bash_profile files, but rather reads, and executes, the .bashrc file instead. Create the .bashrc file now:

cat > ~/.bashrc << "EOF"
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
EOF

Important

Several commercial distributions add an undocumented instantiation of /etc/bash.bashrc to the initialization of bash. This file has the potential to modify the lfs user's environment in ways that can affect the building of critical LFS packages. To make sure the lfs user's environment is clean, check for the presence of /etc/bash.bashrc and, if present, move it out of the way. As the root user, run:

[ ! -e /etc/bash.bashrc ] || mv -v /etc/bash.bashrc /etc/bash.bashrc.NOUSE

When the lfs user is no longer needed (at the beginning of "chapter-chroot-temporary-tools"), you may safely restore /etc/bash.bashrc (if desired).

Note that the LFS Bash package we will build in the section called “Bash-5.3” is not configured to load or execute /etc/bash.bashrc, so this file is useless on a completed LFS system.

For many modern systems with multiple processors (or cores) the compilation time for a package can be reduced by performing a "parallel make" by telling the make program how many processors are available via a command line option or an environment variable. For instance, an Intel Core i9-13900K processor has 8 P (performance) cores and 16 E (efficiency) cores, and a P core can simultaneously run two threads so each P core are modeled as two logical cores by the Linux kernel. As the result there are 32 logical cores in total. One obvious way to use all these logical cores is allowing make to spawn up to 32 build jobs. This can be done by passing the -j32 option to make:

make -j32

Or set the MAKEFLAGS environment variable and its content will be automatically used by make as command line options:

export MAKEFLAGS=-j32

Important

Never pass a -j option without a number to make or set such an option in MAKEFLAGS. Doing so will allow make to spawn infinite build jobs and cause system stability problems.

To use all logical cores available for building packages in 'chapter-cross-tools' and 'chapter-temporary-tools', set MAKEFLAGS now in .bashrc:

cat >> ~/.bashrc << "EOF"
export MAKEFLAGS=-j$(nproc)
EOF

Replace $(nproc) with the number of logical cores you want to use if you don't want to use all the logical cores.

Finally, to ensure the environment is fully prepared for building the temporary tools, force the bash shell to read the new user profile:

source ~/.bash_profile