This list contains awesome OS related stuff. It contains open source operating sytems and hobby operating systems as one can study their code and learn from them.
- 9front - A fork of Plan 9, designed for distributed, networked computing.
- ackOS - A simple 64-bit operating system.
- AROS - Research Operating System is a lightweight, efficient, and flexible desktop operating system, designed to help you make the most of your computer. It's an independent, portable and free project, aiming at being compatible with AmigaOS at the API level
- BoneOS- OS for everyone built by everyone
- Bottlerocket OS- Linux-based OS meant for hosting containers.
- Cadex OS - a simple operating system kernel originally made by Prof. Douglas Thain at the University of Notre Dame and students
- ChibiOS - a complete development environment for embedded applications including RTOS, an HAL, peripheral drivers, support files and tools
- Clive - A unikernel OS inspired by Plan9 and Nix developed at Universidad Rey Juan Carlos of Madrid
- CollapseOS - Bootstrap post-collapse technology
- dahliaOS- dahliaOS is a modern, secure, lightweight and responsive operating system, combining the best of GNU/Linux and Fuchsia OS.
- eggos - A Go unikernel running on x86 bare metal
- Embox - Configurable operating system kernel designed for resource constrained and embedded systems.
- FreeRTOS, GitHub - IoT operating system for microcontrollers, by Amazon.
- Genode - A FOSS operating system framework consisting of a microkernel abstraction layer and a collection of userspace components
- gopher-os - A proof of concept OS kernel written in Go
- GreenteaOS, Github - A free OS designed to be compatible with Windows executables
- HarveyOS - A distributed operating system
- HelenOS - multikernel multiserver OS
- helium - A BSD-based OS project that aims to provide an experience like and some compatibility with macOS
- Hubris - Hubris is an operating system for microcontrollers developed by Oxide Computer Company in Rust
- Interim - Minimalist OS with concepts from Lisp machines and Plan9
- Jehanne, GitHub - OS inspired by Plan9, 9front and Harvey OS
- KnightOS - for z80 calculators
- L4re - Operating system and hypervisor for security/safety-critical and virtualization-enabled applications.
- managarm - Pragmatic microkernel-based OS with fully asynchronous I/O
- Mimiker, GitHub - Simple unix-like operating system for education and research purposes. MIPS microkernel.
- Minoca OS - General purpose OS, written in C
- Nanos - Unikernel that is linux-compatible, written in C
- NodeOS - OS using NodeJS and Linux
- opuntiaOS - an operating system targeting x86, ARMv7, Aarch64.
- orange_slice - A research kernel and hypervisor attempting to get fully deterministic emulation with minimum performance cost. In Rust
- Pidi OS - Independent and minimalistic OS
- Plan 9 from Bell Labs - An OS from the creators of Unix, extending the Unix philosophy of "everything is a file" with a network-centric file system, namespaces and distributed computing.
- Redox - written in Rust
- Sanos, GitHub - Sanos is a minimalistic 32-bit x86 operating system kernel for network server appliances running on standard PC hardware.
- skiftOS, GitHub - A simple, handmade, operating system with a graphical user interface.
- Sculpt OS - Genode based OS
- soso - Simple unix-like operating system written in Nasm assembly and mostly in C
- SynestiaOS - 32/64 bit operating system written in C for arm platform
- Thor - 64bit operating system mostly written in C++
- Theseus - A modern experimental OS written from scratch in Rust to explore novel OS structure and state management techniques.
- tilck - A Tiny Linux-Compatible Kernel.
- tock, GitHub - A secure embedded operating system for microcontrollers
- Unikraft - A modular unikernel for specialization, high efficiency, performance, and security; Linux/POSIX-compatible; mostly in C
- Mimosa, GitHub - Research Operating System that runs Scheme on bare-metal
- hhuOS - hhuOS is a small operating system written in C++ and Assembler for the x86-architecture. The main purpose of this project is to show how different aspects of operating systems theory can be implemented and linked together. The system is not aimed to be a full-featured operating system for daily use.
- AquilaOS - Operating System that is designed to be POSIX compliant and mostly ISA transparent
- Animal - 32 bit multithreaded operating system (formerly Gramado)
- Brutal, GitHub - An operating system inspired by brutalist design that combines the ideals of UNIX from the 1970s with modern technology and engineering
- Cyjon - pure x64 assembly language operating system
- emerald - An operating system kernel written for fun in C
- HalideOS - experimental operating system written entirely from scratch.
- hydrogen - toy OS. 64-bit, preemptive multitasking kernel supporting EFI, PCIe, SATA, framebuffer graphics mode, HFS+.
- JSD-OS - A small operating system for 32 bit x86.
- KripayaOS - x86 Kernel with it's own bootloader.
- KolibriOS - MenuetOS fork
- LemonOS, GitHub - UNIX-like 64-bit operating system written in C++.
- lyre - x86 kernel and distribution powered by mlibc, GNU userland tools, and other common *nix software.
- Mako - Hobby OS for x86 from scratch, written in C
- MenuetOS - Hobby OS supporting 32 and 64 bit, written in Assembly language
- MeetixOS - A hobby OS written in modern C++20 which aims to be Unix-like.
- mOS - A hobby operating system developed from scratch
- moros - MOROS is a hobby operating system written in Rust for the x86 architecture.
- MyXomycota - Monolithic kernel in C
- nopeos - Simple OS kernel with BASIC interpreter for x86
- oneOS - x86-32 and ARMv7 kernel with pre-emptive multi-threading, window manager and editor
- pranaOS - A unix operating system written from scratch in c / c++
- PathOS - Hobby OS based on MikeOS, written in Assembly Language
- PonyOS, GitHub - ToaruOS-based, My Little Pony themed OS
- PouplyOS - Simple OS for fun and learning, named after the ESISAR mascot Poulpy
- r3 - A hobby x86_64 Operating System kernel written in Rust -- with minimal functionalities
- Serenity - Graphical Unix-like operating system for x86 computers
- SimpleOS - Simple Operating System coded in C and Assembly
- Snowdrop OS - a homebrew operating system from scratch, in assembly language
- Sortix - Hobby OS in C and C++ by Jonas 'Sortie' Termansen
- TempleOS - Religious OS :-)
- TETRIS-OS - An operating system, but it only plays Tetris.
- ToaruOS - Hobby operating system from scratch
- Týndur - Hobby operating system build by the Lowlevel community. Written in C and Pascal
- Ultron OS - x86 Operating System written in C++, High School Project
- Visopsys - Open Source Hobby OS developed since 1997
- willOS - A minimal 64 bits kernel (Operating System that cannot "operate" a lot of things)
- Windows 95 in Electron - Hobby Windows 95 implementation in Electron
- Xv6 - A teaching operating system developed in the summer of 2006 for MIT's operating systems course
- BareMetal, GitHub - 64 bit operating system written in Assembly for x86-64
- ZealOS - The Zeal Operating System is a modernized, professional fork of the 64-bit Temple Operating System, TempleOS.
- Darwin XNU - The XNU kernel source code for use in MacOS and iOS
- FreeBSD, Github - Unix-like operating system based on the BSD
- FreeDOS - DOS compatible OS
- Haiku - BeOS inspired OS
- Linux - Linux kernel
- Minix, Github - Unix-like operating system based on a microkernel architecture
- MS-DOS - The original sources of MS-DOS 1.25 and 2.0
- NetBSD, Github - Unix-like operating system based on the BSD
- OpenBSD, Github - Unix-like operating system based on the BSD
- ReactOS, Github - A free Windows-compatible Operating System
- SystemV - AT&T UNIX System V Source Code
- How to Make a Computer Operating System - in C++
- Intermezzos - A follow along book to build IntermezzosOS in Rust
- Linux Kernel in a Nutshell - Covers the entire range of kernel tasks, available as chapters or one PDF
- The little book about OS development by Erik Helin and Adam Renberg
- Think OS - A Brief Introduction to Operating Systems by Allen B. Downey
- Operating System Development Series - OS from the ground up in C
- Operating Systems: Three Easy Pieces - Easy to read book covering virtualization, concurrency and persistence
- xv6: a simple, Unix-like teaching operating system - Book for Xv6
- Operating Systems: From 0 to 1 - Bootstrap yourself to write an OS from scratch by Do Hoang Tu
- Baking Pi – Operating Systems Development by University of Cambridge
- Build a minimal multi-tasking OS kernel for ARM from scratch by Jim Huang
- Bran's Kernel Development by Brandon Friesen
- How to write a Linux kernel patch and submit it by Greg Kroah-Hartman
- Presentation on how the Linux kernel is developed by Greg Kroah-Hartman
- os-tutorial - How to create an OS from scratch by Carlos Fenollosa
- Roll your own toy UNIX-clone OS by James Molloy
- Writing an OS in Rust by Philipp Oppermann
- Making a RISC-V Operating System using Rust by Stephen Marz
- Operating systems development for Dummies by Leo Whitehead
- Kernels 101 – Let’s write a Kernel by Arjun Sreedharan
- Kernels 201 - Let’s write a Kernel with keyboard and screen support by Arjun Sreedharan
- Writing a Tiny x86 Bootloader by Joe Bergeron
- Writing a Bootloader by Alex Parker
- Learning operating system development using Linux kernel and Raspberry Pi
- Genodians - Stories around the Genode Operating System
- os-dev - Wiki with everything you need to know
- Lowlevel - A wiki about creating an OS from scratch. In German
- POSIX - Standards for maintaining compatibility between operating systems
- The benefits and costs of writing a POSIX kernel in a high-level language by Cody Cutler, M. Frans Kaashoek, and Robert T. Morris, MIT CSAIL
- Running Scheme On Bare Metal by Samuel Yvon, Marc Feeley, Scheme 2020
- Unikraft: Fast, Specialized Unikernels the Easy Way by Kuenzer et al., EuroSys 2021
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OldLinux - A Heavily Commented Linux kernel source and more