A Beginner's Guide to Linux From Scratch

February 16, 2021

Objective

Gain a top-level understanding of how Linux works and its foundational principles.
Gather useful tips and tricks from someone who has already gone through the process.
Learn to install Linux on any hardware without using ISO images.

For reference, I have used the following blogs, which provide some of the best open-source documentation available:

Linux From Scratch

My Host Machines During Compilation

Round 1: Dedicated host with base OS as Ubuntu
Round 2: Ubuntu VM installed on a base Ubuntu-operated laptop

Let's Get Started

Step 1: Creating a Dedicated Partition for LFS Compilation and Base Installation

We will compile all the packages needed to build a Linux system and install our Linux OS in the same directory.

The utility I used to make partitions is an app called Gparted, which is preinstalled in the Ubuntu flavor.

Here's a quick overview of the partition setup:

Root mount: /dev/sda1
Swap memory: 8GB partition /dev/sda5
Unallocated space: 20GB for LFS compilation and installation (recommended to create a partition of about 30–35 GB).

Commands for Partition Setup:

export LFS=/mnt/lfs
mkdir $LFS
echo $LFS # should output /mnt/lfs
mkdir $LFS/sources
mkdir $LFS/tools
ln -sv $LFS/tools /

Step 2: Download LFS Binaries from Official LFS Repos

cd $LFS/sources
wget http://www.linuxfromscratch.org/lfs/downloads/8.4/wget-list
wget http://www.linuxfromscratch.org/lfs/downloads/8.4/md5sums
 
pushd $LFS/sources
md5sum -c md5sums

The above command should return all packages checked with "OK" as a result.

Step 3: Adding LFS User and Setting Up the Environment

groupadd lfs
useradd -s /bin/bash -g lfs -m -k /dev/null lfs
passwd lfs # Give a password for lfs user login
 
chown -v lfs $LFS/tools
chown -v lfs $LFS/sources

Environment Setup:

su - lfs
 
cat > ~/.bash_profile << "EOF"
exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
EOF
 
cat > ~/.bashrc << "EOF"
set +h
umask 022
LFS=/mnt/lfs
LC_ALL=POSIX
LFS_TGT=$(uname -m)-lfs-linux-gnu
PATH=/tools/bin:/bin:/usr/bin
export LFS LC_ALL LFS_TGT PATH
EOF
 
source ~/.bash_profile
echo $LFS # should return /mnt/lfs

Step 4: General Steps for the Compilation Process

For compiling all the packages/binaries, follow these steps:

cd $LFS/sources
tar -xvf <package-name/binary-name.tar.gz>
cd <package-name/binary-name>
./configure <with required options> && make
make check # (optional for packages with test cases)
make install
rm -rf <package-name/binary-name>

Compile all packages in the exact order given below and follow every step mentioned in the LFS book:

Linux From Scratch - Book

Example Packages to Compile:

Binutils-2.32 — Pass 1
GCC-8.2.0 — Pass 1
Linux-4.20.12 API Headers
Glibc-2.29
Libstdc++ from GCC-8.2.0
... (and many more as listed in the LFS book)

Step 5: Continued Compilation

Continue compiling the next set of packages as mentioned in the LFS book. Ensure you follow the exact sequence and steps.

Step 6: Udev, Hostname, IP Configuration, and Final Steps for Booting Linux

After compiling the Linux kernel, it's essential to set up network scripts correctly to maintain connectivity.

Final Command for Boot Configuration:

cat > /boot/grub/grub.cfg << "EOF"
# Begin /boot/grub/grub.cfg
set default=0
set timeout=5
 
insmod ext2
set root=(hd0,2)
 
menuentry "GNU/Linux, Linux 4.20.12-lfs-8.4" {
        linux   /boot/vmlinuz-4.20.12-lfs-8.4 root=/dev/sda2 ro
}
EOF

General Tips for the Entire Journey

Don’t deviate from the book at any point.
Write sensible network configuration scripts if your host system is not accessible geographically.
Be patient and maintain a positive attitude throughout the process.

Conclusion

Thanks for reading my blog. Keep coding, keep smiling!