I love using macOS as my personal OS. Redox - Unix-like Operating System written in Rust. (Web) Toddler - Well-designed usable and portable microkernel OS. OS67 - Unix-like toy kernel. Resea - Pure microkernel-based hackable operating system written from scratch in C and Rust. Rux - Hobbyist microkernel written in Rust, featuring a capability-based system similar to seL4. redshirt - Experiment to build some kind of operating-system-like environment where executables are all in WASM and are loaded from an IPFS-like decentralized network. mikado - RISC-V Experimental OS. mkernel - Minimalist kernel which prints "my first kernel" on the screen and then hangs. (HN) Barebones - Barebones multiboot kernel for beginners. xv6 - Re-implementation of Dennis Ritchie's and Ken Thompson's simple, Unix-like teaching operating system. (PDF) (HN) (HN 2) (Lobsters) Orange Slice - Research kernel and hypervisor attempting to get fully deterministic emulation with minimum performance cost. Cloud Hypervisor - Open source Virtual Machine Monitor (VMM) that runs on top of KVM. RancherOS - Tiny Linux distro that runs the entire OS as Docker containers. Bottlerocket OS - Free and open-source Linux-based operating system meant for hosting containers. XNU kernel - Part of the Darwin operating system for use in macOS and iOS operating systems. Pebble - Microkernel and userspace written in Rust, with first-class message passing. Distaff - Zero-knowledge virtual machine written in Rust. zCore - Reimplement Zircon microkernel in Rust. lilith - POSIX-like x86-64 kernel and userspace written in Crystal. Genode - Operating System Framework. Shrine - TempleOS distro for heretics. Subgraph OS - Desktop computing and communications platform that is designed to be resistant to network-borne exploit and malware attacks. (Handbook) Mezzano - Operating system written in Common Lisp. (HN) LegoOS - Disseminated, Distributed OS for Hardware Resource Disaggregation. CuBitOS - General-purpose, formally-verified, 64-bit operating system in SPARK/Ada for x86-64. Demikernel - Library operating system architecture designed for use with kernel-bypass I/O devices. Drone - Embedded Operating System for writing real-time applications in Rust. (drone-core) Manticore - Research operating system, written in Rust. (Web) CyanOS - x86 monolithic kernel operating system, coded in C++ 17 and few lines of x86 Assembly. ChaiOS - Modular multi-platform hobby OS. Hybrid kernel, largely monolithic. Kernel C library is dynamically linked. Tails - Portable operating system that protects against surveillance and censorship. (Intro) EmuTOS - Free operating system for Atari ST computers, and more. (Web) HalideOS - Experimental operating system written entirely from scratch. It supports a basic shell with some commands including a command line calculator. Biscuit - Monolithic, POSIX-subset operating system kernel in Go. (HN) (Code) illumos - Unix operating system which provides next-generation features for downstream distributions, including advanced system debugging, next generation filesystem, networking, and virtualization options. (Rise and Development of illumos) EggOS - Go unikernel running on x86 bare metal. (HN) KnightOS - Third-party operating system for TI calculators. eduOS-rs - Teaching operating system written in Rust. (Web) Theseus OS - New OS written from scratch in Rust to experiment with novel OS structure, better state management, and how to shift OS responsibilities like resource management into the compiler. (HN) CactusOS - Simple operating system that is aimed to not be anything like linux. Zephyr - New generation, scalable, optimized, secure RTOS for multiple hardware architectures. (Docs) Cosmos - Operating system "construction kit". Build your own OS using managed languages such as C#, VB.NET, and more. (Web) MollenOS - Modern operating system that is built with focus on abstraction and a modular design. Azure RTOS ThreadX - Advanced real-time operating system (RTOS) is designed specifically for deeply embedded applications. HelenOS - Portable microkernel-based multiserver operating system written from scratch. (Web) bootloader - Experimental x86 bootloader written in Rust and inline assembly. Cyjon - Simple, clean, multi-tasking operating system written in pure assembly language for 64-bit processors from the AMD64 family. Contiki - Open source operating system that runs on tiny low-power microcontrollers. OSv - Modular unikernel designed to run applications securely on micro-VMs . (Code) (HN) (HN 2) Rumprun - Uses rump kernels to provide the Rumprun unikernel. Rumprun works on not only on hypervisors such as KVM and Xen, but also on bare metal. Rump Kernels - Enable you to build the software stack you need without forcing you to reinvent the wheels. mOS - Unix-like operating system developed from scratch and aims to POSIX compliant. pdp7-unix - Project to resurrect Unix on the PDP-7 from a scan of the original assembly code. core-os-riscv - xv6-like operating system on RISC-V with multi-core support. rCore - Rust version of THU uCore OS. Linux compatible. Eltanin - Free, simple, and complete general-purpose operating system. skiftOS - Simple, handmade, operating system with a graphical user interface. (Web) ChrysaLisp - Parallel OS, with GUI, Terminal, OO Assembler, Class libraries, C-Script compiler, Lisp interpreter and more. (HN) Pluto - x86 kernel written in Zig. LeOS Kernel - Kernel project for operating system for ARM 64bit (AArch64) written in Rust. (Web) Mimosa - Operating system consists of a minimal kernel built on C++ and Scheme. daintree - ARMv8-A operating system, plus a UEFI bootloader, all written in Zig. AROS - Lightweight, efficient, and flexible desktop operating system. (HN) M3 - Microkernel-based system for heterogeneous manycores. Helium - BSD-based OS project that aims to provide an experience like and some compatibility with macOS. Harvey - Distributed operating system. (Web) TypOS - Operating system for typechecking processes. KolibriOS - Tiny yet incredibly powerful and fast operating system. (HN) Kerla - New operating system kernel with Linux binary compatibility written in Rust. rustboot - Tiny 32 bit kernel written in Rust. WINIX OS - UNIX-style Operating System for the Waikato RISC Architecture Microprocessor. (HN) Aquila OS - Complete Operating System (kernel + system) that is designed to be POSIX compliant and mostly ISA transparent. (Web) FuzixOS - Because Small Is Beautiful. Multics - Pioneering operating system, commonly considered the "progenitor" of the UNIX operating system. (Code) Tilck - Tiny Linux-Compatible Kernel. Airyx OS - BSD-based OS project that aims to provide an experience like and some compatibility with macOS. (Code) (HN) (Lobsters) (HN) Lemon OS - UNIX-like 64-bit operating system written in C++. (Code) SteinsOS - Operating system featuring non-preemptive single-threaded kernel targeting on armv8. EmbassyOS - Graphical operating system for running self-hosted software. (Web)
We have moved away from a world of shared libraries, filesystems, and UNIX users and permissions into a world of shared-nothing (no shared memory, no shared filesystem), capabilities, new and extremely aggressive attack vectors, and a need to compartmentalize and virtualize at more fundamental layers even if it comes at a performance penalty. You can't retrofit a microkernel-like abstraction on top of Linux. At the same time, a lot of the features you need for a shared multi-user system are basically cruft for modern mobile, single-user systems with little use for shared resources (not saying they're not shared; it's just that you can no longer trust apps installed in the user system so expecting apps to behave nicely is out of the window). The new wave of OSes embraces formal correctness when possible, JIT, garbage-collected application programming languages, tightly-enforced resource boundaries, deny-by-default security models, provably-safe system programming languages (Rust and whatever else will come), immutability and copy-on-write at the cost of filesystem space, and secure memory abstractions for more RAM.
mirageOS - A programming framework for building type-safe, modular systems. Raspberry Pi OS - Learning operating system development using Linux kernel and Raspberry Pi. Unik - Unikernel & MicroVM Compilation and Deployment Platform. SPDK - Storage Performance Development Kit Provides a set of tools and libraries for writing high performance, scalable, user-mode storage applications. Nanos - New kernel designed to run one and only one application in a virtualized environment. BootOS - Monolithic operating system in 512 bytes of x86 machine code. (HN) Soso - Simple unix-like operating system written in Nasm assembly and mostly in C. swieros - Tiny and fast Unix-ish kernel (based on xv6), compiler, and userland for fun, education, and research. ioping - Simple disk I/0 latency measuring tool. Awesome eBPF - BPF, as in Berkeley Packet Filter, is an in-kernel virtual machine running programs passed from user space. Krabs - x86 bootloader written in Rust. oreboot - Fork of coreboot, with C removed, written in Rust. fectl - Client/server system that allows its users to monitor and control a number of processes on UNIX-like operating systems. HiddenVM - Use any desktop OS without leaving a trace. Solo5 - Sandboxed execution environment for unikernels. Mbox - Lightweight sandboxing mechanism that any user can use without special privileges in commodity operating systems. (Code) Albatross - Orchestrate and manage MirageOS unikernels with Solo5. Zub VM - Super-fast, stack-based virtual machine for dynamic languages. Tibru - Alternative to the nonsense that is the Urbit project. (Lobsters) Tarides - Building functional systems. Commercial support on MirageOS and Irmin. Vulnerable Kext - WIP "Vulnerable by Design" kext for iOS/macOS to play & learn OS kernel exploitation. (Web) RVM 1.5 - Type-1.5 hypervisor written in Rust. OpenRC - Dependency-based init system that works with the system-provided init program, normally /sbin/init. pyvmidbg - LibVMI-based GDB server, implemented in Python. libmicrovmi - Cross-platform unified interface on top of hypervisor's VMI APIs. crosvm - Chrome OS Virtual Machine Monitor. Rust VM - Virtual Machine written in Rust to emulate the LC3 computer (Little Computer 3). Sudo - Program designed to allow a sysadmin to give limited root privileges to users and log root activity. iceoryx - Inter-process-communication middleware that enables virtually limitless data transmissions at constant time. (Web)