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='\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=$LFS/usr/share/config.site
export LFS LC_ALL LFS_TGT PATH CONFIG_SITE
EOF
The meaning of the settings in .bashrc
-
set +h -
The set +h command turns off bash's hash function. Hashing is ordinarily a useful feature—bash uses a hash table to remember the full path to executable files to avoid searching the
PATHtime and again to find the same executable. However, the new tools should be used as soon as they are installed. Switching off the hash function forces the shell to search thePATHwhenever a program is to be run. As such, the shell will find the newly compiled tools in$LFS/tools/binas soon as they are available without remembering a previous version of the same program provided by the host distro, in/usr/binor/bin. -
umask 022 -
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).
-
LFS=/mnt/lfs -
The
LFSvariable should be set to the chosen mount point. -
LC_ALL=POSIX -
The
LC_ALLvariable controls the localization of certain programs, making their messages follow the conventions of a specified country. SettingLC_ALLto “POSIX” or “C” (the two are equivalent) ensures that everything will work as expected in the cross-compilation environment. -
LFS_TGT=$(uname -m)-lfs-linux-gnu -
The
LFS_TGTvariable sets a non-default, but compatible machine description for use when building our cross-compiler and linker and when cross-compiling our temporary toolchain. More information is provided by Toolchain Technical Notes. -
PATH=/usr/bin -
Many modern Linux distributions have merged
/binand/usr/bin. When this is the case, the standardPATHvariable should be set to/usr/bin/for the Chapter 6 environment. When this is not the case, the following line adds/binto the path. -
if [ ! -L /bin ]; then PATH=/bin:$PATH; fi -
If
/binis not a symbolic link, it must be added to thePATHvariable. -
PATH=$LFS/tools/bin:$PATH -
By putting
$LFS/tools/binahead of the standardPATH, the cross-compiler installed at the beginning of Chapter 5 is picked up by the shell immediately after its installation. This, combined with turning off hashing, limits the risk that the compiler from the host is used instead of the cross-compiler. -
CONFIG_SITE=$LFS/usr/share/config.site -
In Chapter 5 and Chapter 6, if this variable is not set, configure scripts may attempt to load configuration items specific to some distributions from
/usr/share/config.siteon the host system. Override it to prevent potential contamination from the host. -
export ... -
While the preceding commands have set some variables, in order to make them visible within any sub-shells, we export them.
![[Important]](../images/important.png)
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 7), you may safely restore /etc/bash.bashrc (if desired).
Note that the LFS Bash package we will build in Section 8.36, “Bash-5.2.37” 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 5
and Chapter 6,
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