Kernel OS

This project is a custom, bare-metal Linux operating system built entirely from scratch. Instead of taking a heavy, pre-configured distribution, this project starts from an absolute blank slate (allnoconfig) and surgically adds only the drivers and subsystems required to boot a fully functional terminal environment.

The entire build process is automated through bash scripts and a GitHub Actions CI/CD pipeline.

The Architecture

The OS is divided into two decoupled components: the Kernel and the Userland. The automation is handled by two independent scripts located in the setup/ directory:

• setup/linux-kernel.sh: This script downloads the Linux kernel source and strips away all default configurations. It then injects only the essential drivers (like TTY for the terminal, i8042 for PS/2 keyboard input, and VGA for the display) and compiles them into a single, bootable bzImage.
• setup/busybox.sh: This script handles the userland. It downloads BusyBox, configures it as a static binary, and bypasses known compile errors (like disabling the tc network utility). It then creates the fundamental Linux folder structure (/dev, /proc, /sys), writes the init daemon configuration (inittab), and packs everything into a compressed RAM disk (initramfs.cpio.gz).

The Reasons

Here are a few core engineering decisions made during this project:

• Why start with allnoconfig? It is easy to compile a kernel with default settings. Starting with an empty configuration proves a deeper understanding of how the kernel actually interacts with the hardware (like manually bridging the PS/2 bus to the virtual keyboard).
• Why embed the Kernel Command Line? Instead of passing a long, messy -append string through QEMU to configure the boot sequence, the boot parameters (console=tty0 quiet loglevel=3 no-reboot) are compiled directly into the kernel binary. This makes the final OS completely self-contained.
• Why use an Arch Linux container in CI/CD? To automate the releases, the GitHub Actions workflow runs inside an Arch Linux Docker container. Using pacman -Syu ensures the build environment is perfectly synced with the latest rolling release, preventing any partial-upgrade dependency breaks during compilation.

Execution Instructions

You can download the pre-compiled bzImage and initramfs.cpio.gz from the Releases section of this repository, or you can build it locally.

How to Build Locally

If you want to compile the OS on your own machine, ensure you have standard build tools installed (e.g., base-devel, bc, cpio, curl, and qemu).

1. Clone the repository:

git clone https://github.com/shivjeet1/kernel-os.git 
cd kernel-os

2. Make the scripts executable:

chmod +x setup/linux-kernel.sh
chmod +x setup/busybox.sh

3. Run the builds:

# Locally build the kernel and userland
./setup/linux-kernel.sh
./setup/busybox.sh

The compiled artifacts will be saved in the /output directory.

How to Run the OS

Once you have the bzImage and initramfs.cpio.gz (either built locally or downloaded from Releases), you can boot the OS using QEMU.

Run the following command from the same directory as your artifacts:

qemu-system-x86_64 \
    -kernel bzImage \
    -initrd initramfs.cpio.gz \
    -no-reboot

To shut down the OS: Simply type reboot inside the BusyBox terminal. The init daemon will safely unmount the filesystems, halt the kernel, and cleanly exit the QEMU window.