Custom Linux Kernel and Busybox Setup#

Step 1: Install Dependencies#

First things first, let’s make sure we have all the necessary tools and packages. Depending on your distribution, run one of the following commands:

• For Debian-based systems:

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  sudo apt-get install bzip2 git vim make gcc libncurses-dev flex bison bc cpio libelf-dev libssl-dev syslinux dosfstools nano git
  

• For Fedora-based systems:

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  sudo dnf install bzip2 git vim make gcc ncurses-devel flex bison bc cpio elfutils-libelf-devel openssl-devel syslinux dosfstools nano git
  

Step 2: Clone the Linux Kernel Repository#

Let’s get our hands on the Linux Kernel source code. Clone Linus Torvalds’ repository like a boss:

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git clone --depth 1 https://github.com/torvalds/linux.git
2
cd linux

Step 3: Configure the Kernel#

Time to customize our kernel to fit our needs. Execute the following command and brace yourself for the configuration menu:

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make menuconfig

Feel free to tweak the settings to your heart’s content and then save your changes.

Step 4: Build the Kernel#

Let the compilation begin! Execute the following command to build your shiny new kernel:

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make -j 4

Adjust the -j parameter according to your processor count for maximum efficiency.

Step 5: Copy Kernel Image#

Keep your precious kernel image safe. Create a cozy directory for it and copy the image there:

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mkdir /boot-files
2
cp arch/x86/boot/bzImage /boot-files

Step 6: Clone Busybox#

Next up, let’s grab Busybox for our userspace utilities. Clone the repository like a pro:

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git clone --depth 1 https://git.busybox.net/busybox
2
cd busybox

Step 7: Configure Busybox#

Time to configure Busybox. Fire up the configuration menu:

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make menuconfig

Select “Build static binary” because we like our binaries like we like our relationships – stable.

Step 8: Build Busybox#

Get ready to witness the magic. Build Busybox with this command:

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make -j 4

Step 9: Create Initramfs#

Let’s prep an initial RAM filesystem (initramfs) for our kernel to play with after boot:

1
mkdir /boot-files/initramfs
2
make CONFIG_PREFIX=/boot-files/initramfs install
3
cd /boot-files/initramfs/
4
nano init

Add the following content to the init file:

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#!/bin/sh
2
/bin/sh

Then, let’s do some cleanup and packing:

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rm linuxrc
2
chmod +x init
3
find . | cpio -o -H newc > ../init.cpio

Step 10: Prepare Boot Environment#

Time to get our boot environment ready. Install syslinux and create a bootable file system:

1
sudo apt-get install syslinux
2
dd if=/dev/zero of=boot bs=1M count=50
3
ls
4
sudo apt-get install dosfstools
5
mkfs -t fat boot
6
syslinux boot
7
mkdir m && mount boot m
8
cp bzImage init.cpio m

Step 11: Finalize Boot Environment#

Finish up the boot setup by unmounting the file system:

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umount m

And there you have it! Your custom Linux OS is ready to rock and roll. Just add the following configuration in the boot section:

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boot: /bzImage -initrd=/init.cpio

Now sit back, relax, and watch your custom creation come to life. Happy hacking!

Contributors: @mranv, @Teztarrar