Linux 0.01 Analysis Environment

This project builds and runs Linux 0.01 on the Bochs emulator to analyze the entire kernel from source. Detailed analysis is documented on my blog.

Motivation

The modern Linux kernel is too large to trace end-to-end. Linux 0.01 fits the entire kernel — bootloader, scheduler, filesystem, and more — into just a few thousand lines, making it possible to follow exactly how each component works and how they fit together. Running it on an emulator makes the analysis even more practical. Bochs has a built-in debugger that lets you inspect CPU registers, memory, and interrupt flow in ways that simply aren't possible on real hardware.

Source

The Linux 0.01 source in this repository is based on a version patched for modern compilers.

• Original reference: https://github.com/mariuz/linux-0.01

Repository Structure

.
├── bochsrc.txt          # Bochs configuration file
├── create_hdb.sh        # Script to create the Minix disk image (hdb.img)
├── hdb.img.tar.gz       # Pre-built disk image (ready to use)
├── commands.tar.gz      # Linux 0.01-compatible command binaries (echo, pwd, etc.)
├── sh.tar.gz            # Linux 0.01-compatible shell binary
└── linux-0.01/          # Linux 0.01 source code
    ├── boot/            # Boot sector and kernel initialization
    ├── kernel/          # Interrupts, traps, system calls
    ├── mm/              # Memory management
    ├── fs/              # Minix filesystem
    ├── init/            # Kernel entry point (main.c)
    ├── include/         # Header files
    ├── lib/             # Utilities
    └── tools/           # Boot image generation tools

hdb.img.tar.gz is a pre-built disk image that already includes the shell and command binaries from sh.tar.gz and commands.tar.gz. You can use it directly without building anything.

The binaries in commands.tar.gz and sh.tar.gz are sourced from draconux.free.fr.

Requirements

Tested on

	Version
OS	Ubuntu 22.04 / 24.04
GCC	11.04 or later
Bochs	2.6.11

Kernel build dependencies:

sudo apt install -y \
  build-essential \
  gcc-multilib \
  libc-dev \ 
  bin86 \
  util-linux

Bochs build dependencies:

sudo apt install -y \
  libsdl2-dev \
  libx11-dev \
  bison \
  nasm \
  flex \
  pkg-config \
  libreadline-dev \
  bcc

Bochs configure options:

./configure \
  --enable-debugger \
  --enable-show-ips \
  --with-sdl2 --with-x --with-x11 \
  --enable-cpu-level=6 \
  --enable-all-optimizations

Quick Start

1. Build the kernel

cd linux-0.01
make
cd ..

make generates an Image file inside linux-0.01/, which is used as the floppy disk image by Bochs.

2. Prepare the disk image

Using the pre-built image:

tar xzf hdb.img.tar.gz

Building from scratch:

sudo ./create_hdb.sh

3. Run

bochs -q -f bochsrc.txt

Blog

• seojuncha.github.io