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Embedded Linux From Scratch (ARM + QEMU)

Project Overview

This project demonstrates building an Embedded Linux system completely from scratch for an ARM target without using build systems like Buildroot or Yocto.

The system includes:

  • Custom cross-toolchain (generated using crosstool-NG)
  • U-Boot bootloader
  • Linux Kernel (v6.1)
  • Minimal BusyBox-based root filesystem
  • QEMU emulation using the vexpress-a9 machine

The goal of this project is to understand the complete boot flow and internal components involved in bringing up an embedded Linux system.

qemu emulation

  1. kernel booted sucessfully

alt text

  1. u boot prompt screen

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Target Platform

  • Architecture: ARM (32-bit)
  • QEMU Machine: vexpress-a9
  • Kernel Image: zImage
  • Device Tree: vexpress-v2p-ca9.dtb

Boot Flow

ROM → U-Boot → Linux Kernel (zImage) → Device Tree → Root Filesystem → init → Shell

This project walks through each stage individually.

Repository Structure

  • toolchain/ → Cross-toolchain generation and configuration
  • uboot/ → U-Boot build and configuration
  • kernel/ → Linux kernel build and configuration
  • busybox-rootfs/ → Root filesystem creation
  • qemu/ → QEMU run configuration (to be added)

How To Use This Repository

Follow the components in order:

  1. Build the cross-toolchain from the toolchain/ directory.
  2. Build U-Boot from the uboot/ directory.
  3. Build the Linux kernel from the kernel/ directory.
  4. Create the root filesystem from busybox-rootfs/.
  5. Finally, use the QEMU emulation setup inside the qemu/ directory to boot the complete system.

Each folder contains documentation and scripts required to reproduce the build.

What This Project Covers

  • Cross-compilation for ARM
  • Bootloader configuration and build
  • Kernel configuration and compilation
  • Device tree usage
  • Root filesystem creation
  • Booting via QEMU
  • Debugging early boot issues

Learning Objectives

  • Understand the role of each component in embedded Linux
  • Learn how kernel configuration affects runtime behavior
  • Understand how U-Boot loads and boots the kernel
  • Gain hands-on experience with low-level Linux bring-up

Status

QEMU emulation scripts and final boot integration will be added under the qemu/ directory.

This project is intended for learning and demonstration of embedded Linux fundamentals.