SimpleKernel

This repository contains a minimal 32‑bit kernel that prints a message to the screen. The kernel is multiboot compliant and can be loaded using GRUB. The instructions below describe how to build the kernel and run it in VirtualBox.

Building

You need a few build tools including gcc, nasm, ld, and grub. Because the kernel is 32-bit, the gcc -m32 option must be available. On Debian/Ubuntu systems install the following packages:

sudo apt-get install build-essential nasm grub-pc-bin xorriso gcc-multilib

Alternatively you can use a 32-bit cross-compiler package such as gcc-i686-linux-gnu so that gcc -m32 works.

To build the kernel binary run:

make

This produces a kernel.bin file.

Creating a bootable ISO

Create the GRUB configuration and ISO image with the following commands:

mkdir -p iso/boot/grub
cp kernel.bin iso/boot/kernel.bin
cat > iso/boot/grub/grub.cfg <<CFG
set timeout=0
set default=0

menuentry "SimpleKernel" {
    multiboot /boot/kernel.bin
    boot
}
CFG

grub-mkrescue -o SimpleKernel.iso iso

The resulting SimpleKernel.iso can be used to boot the kernel.

Running in VirtualBox

1. Open VirtualBox and create a new virtual machine. Select Other/Unknown as the OS type and choose 32-bit.
2. Attach SimpleKernel.iso as the optical drive for the VM.
3. Start the VM. GRUB should load and the screen will display the message from the kernel.

The kernel now features a small preemptive round robin scheduler. Two command prompts run in parallel: one echoes back each line and the other prints the word count. Press Tab to switch the focused program. Input is delivered only to the focused prompt while the other continues running in the background.