TinyDOS

A minimalist "Linux From Scratch" style OS with a custom-written, nostalgic DOS-like shell.

https://github.com/minhmc2007/TinyDOS

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🤔 What is TinyDOS?

Imagine booting a modern Linux kernel directly into a nostalgic MS-DOS-like environment. That's TinyDOS.

This is an educational project that explores the fundamentals of a Linux system. By stripping away the complexities of modern distributions, we are left with the bare essentials: a bootloader, a kernel, a minimal userspace, and our own shell.

The heart of the project is the custom init.c shell, which provides a classic command-line experience on top of a powerful, modern Linux kernel.

📸 A Glimpse into TinyDOS

Here's what a typical session looks like. Notice how you can use both built-in DOS commands and standard Linux utilities from BusyBox.

MyTinyDOS v0.0.1 - (c) 2025

C:\> ver
MyTinyDOS Shell [Version 0.0.1 (2025)]
Running on Linux 6.15.2-tinyDOS (x86_64)

C:\> dir
 Directory of C:\

01/01/1970  12:00 AM   <DIR>          .
01/01/1970  12:00 AM   <DIR>          ..
01/01/1970  12:00 AM   <DIR>          bin
01/01/1970  12:00 AM   <DIR>          dev
01/01/1970  12:00 AM   <DIR>          etc
...

C:\> md my_stuff

C:\> cd my_stuff

C:\MY_STUFF> echo Hello from TinyDOS > test.txt

C:\MY_STUFF> type test.txt
Hello from TinyDOS

C:\MY_STUFF> ls -l
-rw-r--r--    1 root     root            21 Jan  1 12:02 test.txt

C:\MY_STUFF> exit
Shutting down system...
[  OK  ] Reached target Power-Off.

✨ Features

System Features

• Custom Linux Kernel: Runs on a custom-configured 6.15.2-tinyDOS kernel.
• BusyBox Userspace: Provides a rich set of essential Unix utilities (ls, vi, mount, free, etc.) in a single binary.
• DOS-like init Shell: The entire user experience is managed by init.c, a custom C program that acts as both the system's init process (PID 1) and the user's shell.
• ISOLINUX Bootloader: Boots from a simple, standard ISO file.
• Automated Build: A single script handles the entire build process.

Built-in Shell Commands

The custom shell implements many classic commands internally. For anything else, it passes the command to the underlying BusyBox environment.

Command	Description
? / HELP	Shows this command reference.
ABOUT	Shows author information.
VER	Shows TinyDOS and Linux kernel version information.
CLS	Clears the screen.
ECHO [msg]	Displays a message to the screen.
DIR [path]	Lists the contents of a directory in DOS format.
CD/CHDIR [path]	Changes or displays the current directory.
MD/MKDIR [path]	Creates a new directory.
RD/RMDIR [path]	Removes an empty directory.
TYPE [file]	Displays the content of a text file.
COPY [src] [dst]	Copies a single file.
XCOPY [src] [dst]	Recursively copies files and directories.
DEL/ERASE [file]	Deletes a file.
REN/MOVE [src]	Renames or moves a file or directory.
EDIT [file]	Opens the file in MiniEdit, TinyDOS's C text editor.
REBOOT	Restarts the system.
EXIT/SHUTDOWN	Powers off the system.

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📝 The edit Command and MiniEdit

TinyDOS includes an edit command, which launches the built-in text editor called MiniEdit.

About MiniEdit

• MiniEdit is a C text editor inspired by the best features of both Vim and Nano.
• You can think of it as: miniedit = Vim + Nano.
• It’s simple to use for beginners (like Nano), but also provides efficient navigation and editing shortcuts (like Vim).
• For a detailed look at its implementation and features, see miniedit.c.

Usage

To open MiniEdit, simply run:

edit filename

This opens or creates the file filename in MiniEdit.

Explore and enjoy efficient text editing in TinyDOS!

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🚀 Quick Start: Build & Run

Building and running TinyDOS is incredibly simple thanks to the automated build script.

Step 1: Install Prerequisites

You'll need a standard Linux build environment and QEMU. On Debian/Ubuntu, you can install them with:

sudo apt-get update
sudo apt-get install build-essential git qemu-system-x86 xorriso bc libelf-dev libssl-dev

Step 2: Clone and Build

The build.sh script does everything for you: it downloads sources, compiles the kernel and BusyBox, builds the init program, and generates the final bootable ISO.

git clone https://github.com/minhmc2007/TinyDOS.git
cd TinyDOS
bash build.sh

Step 3: Run!

The script will create bootable.iso. You can run it with QEMU:

qemu-system-x86_64 -cdrom bootable.iso

🔧 Architecture & The Build Process

Understanding the architecture is key to the project's purpose.

1. Boot: ISOLINUX boots the system from the ISO.
2. Kernel: It loads the custom bzImage Linux kernel into memory.
3. Initramfs: The kernel mounts a minimal initial RAM disk which contains the BusyBox binary and our custom init program.
4. Init: The kernel executes /sbin/init (our C program) as the first process (PID 1).
5. Shell: Our init program starts, prints the welcome message, and gives you the C:\> prompt.

The build.sh script automates the entire "Linux From Scratch" style workflow:

• It compiles init.c into a static binary.
• It constructs an initramfs (initial RAM filesystem) containing the necessary directory structure (/bin, /sbin, /dev, etc.) and populates it with BusyBox and our init program.
• Finally, it packages the kernel and the initramfs into a bootable tinydos.iso using xorriso.

Contributing

Contributions make the open-source community an amazing place to learn and create. Any contributions you make are greatly appreciated. Please fork the repo and create a pull request!

1. Fork the Project
2. Create your Feature Branch (git checkout -b feature/AmazingFeature)
3. Commit your Changes (git commit -m 'Add some AmazingFeature')
4. Push to the Branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

License

Distributed under the GNU GENERAL PUBLIC License 3. See the LICENSE file for more information.

Acknowledgements

• The Linux From Scratch project for being the ultimate guide.
• The developers of BusyBox, the Linux Kernel, and SYSLINUX.
• Everyone who loves the nostalgia of the command line.