FOS — ASU Operating Systems 2025/26

FOS is an educational OS for Ain Shams University Operating Systems Course CSW355, forked and refactored from MIT Operating Systems Lab 6.828. It was created by Dr. Mahmoud Hossam and is currently maintained by the course staff. FOSv2 (2025/26 Edition) updates the layout and build flow for this year, featuring modern editor/debugger integration.

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Table of Contents

• 1. What's Different?

• 2. Set up Environment

  • 2.1. Windows - Automatic Setup (Recommended)
  • 2.2. Windows - Cygwin (Deprecated)
  • 2.3. Windows - WSL (Recommended)
  • 2.4. Linux

• 3. Setup Workspace

• 4. Debugging

• 5. Contribute

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1. What's Different?

1. No Eclipse! — Works with any text editor; defaults to Visual Studio Code
2. QEMU instead of Bochs — Faster, fewer configs, and more options
3. Independent source tree — OS code separated from build dependencies
4. Cleanups — JOS leftovers removed
5. Smaller footprint — Unused packages/files dropped
6. Open source — Contributions and fixes welcome
7. New targets — make run (QEMU) and make debug (QEMU+GDB on port 26000) for the 25/26 edition

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2. Set up Environment

FOS requires a Linux-like environment to build and run correctly. On Windows, use the Automatic Setup Script (Recommended) or WSL. ⚠️ Cygwin is deprecated — it no longer works reliably with the modern FOSv2 toolchain and QEMU.

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2.1. Windows - Automatic Setup (Recommended)

Note: Make sure PowerShell is updated to the latest version. After updating, it may be called PowerShell 7 instead of Windows PowerShell.

Step 1: One-Line Install Command

Simply open PowerShell (normal mode, not Administrator) and run:

 Set-ExecutionPolicy Bypass -Scope Process -Force
 irm https://raw.githubusercontent.com/G1DO/fos-windows-setup/main/setup_fos_windows.ps1 | iex

💡 These scripts automate the installation and configuration of all dependencies required to build and run FOS on Windows. For more details or to view the full script, visit G1DO/fos-windows-setup.

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Step 2: Build the Project (Git Bash)

After installation completes:

Open Git Bash (or VS Code terminal using Git Bash) and run:

# 1) Load environment variables
source ~/.bashrc

# 2) Sanity checks (should print valid paths/versions)
which i386-elf-gcc
which qemu-system-i386

# 3) Clone and build FOS
git clone https://github.com/G1DO/fos.git
cd fos
make
make run

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2.2. Windows - Cygwin (Deprecated)

⚠️ Cygwin is outdated and no longer supported.

It frequently breaks with the latest toolchain and QEMU versions. Please use the Automatic Setup Script or WSL instead.

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2.3. Windows - WSL (Recommended)

Requires Windows 10 build 16215+

The Windows Subsystem for Linux lets you run a genuine GNU/Linux environment (tools, utilities, and apps) directly on Windows.

1. Control Panel → Programs → Turn Windows Features on or off → enable Windows Subsystem for Linux
2. Install Ubuntu from Microsoft Store
3. Launch Ubuntu
4. Follow the Linux instructions below

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2.4. Linux

# Required packages
sudo apt-get update
sudo apt-get install -y build-essential qemu-system-i386 gdb libfl-dev

# Optional: cross toolchain
sudo mkdir -p /opt/cross && cd /opt/cross
sudo wget https://github.com/YoussefRaafatNasry/fos-v2/releases/download/toolchain/i386-elf-toolchain-linux.tar.bz2
sudo tar xjf i386-elf-toolchain-linux.tar.bz2 && rm i386-elf-toolchain-linux.tar.bz2
echo 'export PATH="$PATH:/opt/cross/bin"' >> ~/.bashrc
source ~/.bashrc

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3. Setup Workspace

1. Download and install Visual Studio Code

2. Clone this repository and open it in VS Code:

   git clone https://github.com/G1DO/fos.git
   cd fos/
   code .

3. Install all recommended extensions when prompted

4. Build the project using:

   make
   make run

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4. Debugging

1. Add breakpoints to your code
2. Start Debugging → F5
3. Fix your bugs and rerun

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5. Contribute

• Submit a PR with improvements or bug fixes — contributions are always welcome
• Open an Issue if something doesn’t work or needs clarification