Every system listed below is open source and not powered by Linux. Each has an ISO or installer you can boot today, and many of the picks can even run Linux applications.

Think of it as a list of operating systems that are friends with Tux but not friendly enough to call him inside for a cup of tea.

This list is not ranked.

Vinix

If you own an Apple Silicon MacBook and want a system that is neither macOS nor a Linux distribution, Vinix is aimed at you. Only the original M1 is supported today, and Alexander Medvednikov, the author of V, maintains the project.

The kernel is monolithic and written mostly in V, while part of it is C and assembly. Because memory is managed by hand, no garbage collector can interrupt a system call, and the security model borrows certain concepts from OpenBSD.

On ARM64, it runs Alpine Linux binaries natively, and pkg installs packages from Alpine's aarch64 repositories. ISOs for both x86-64 and ARM64 are available for virtual machine use.

A good pick if you enjoy poking at experimental kernels.

Asterina NixOS

Trying Asterinas NixOS means setting up a NixOS system and finding a Rust kernel where Linux should be. Asterinas is that kernel, and because it implements Linux's system call interface, apps for the Linux platform run on it.

The distribution is configured through Nix like regular NixOS, and unsafe Rust is allowed only inside a small framework called OSTD, while the rest of the kernel, along with its drivers, is safe Rust.

x86_64 is the fully supported platform, and ARM64 and RISC-V sit one tier below it. The project says the distro is not ready for production use and aims the installer ISO on GitHub at early adopters and enthusiasts.

A good pick if you follow the implementation of Rust in operating systems.

Redox OS

Where Asterinas swaps Rust in under NixOS, Redox OS builds the whole system from scratch in Rust. It’s a Unix-like OS with a microkernel design, and Jeremy Soller of System76 created and maintains it.

You get the Orbital desktop, a pkg package manager, and several apps from System76’s COSMIC desktop. Linux and BSD software has gotten much easier to port too, and the project has recently been focusing on making Redox boot reliably on real hardware, not just in a virtual machine.

A good pick if you want to see how far a pure Rust operating system has come

FreeBSD

FreeBSD is a complete operating system derived from BSD, the Unix version developed at the University of California, Berkeley. A large community maintains it, and its license lets companies keep their own changes private.

ZFS, jails, and a hypervisor sit at the center of what it offers. OpenZFS is built into the base system, and boot environments let you roll back a bad update by snapshotting the system first.

Its recent release, FreeBSD 15.1, came out earlier this year, and the OS runs on hardware platforms like AMD64, AArch64, Armv7, PowerPC, and RISC-V.

A good pick if you run servers, storage, or networking gear.

GhostBSD

GhostBSD is FreeBSD with the desktop work already done. The project pairs a FreeBSD base with the MATE desktop and offers a set of applications that make users feel familiar with using it.

The name started as shorthand for GNOME hosted by FreeBSD. MATE, the desktop it ships today, is a continuation of GNOME 2, and the old name still fits.

Updates arrive on a slow-rolling schedule, and the project says it values a stable cycle over chasing the newest software the way some Linux distros do. The current release, 26.1-R15.0p2, came out in April on a FreeBSD 15.0 base.

Also good to know is that Linux binary compatibility comes preconfigured, and an installer built on OpenZFS keeps setup approachable for newcomers.

A good pick if you want FreeBSD as an everyday desktop.

Haiku

Haiku is an open source operating system inspired by BeOS that is aimed at personal computing. The same team writes the kernel and the desktop applications, with the project crediting that approach for the system's consistent interface.

Under that interface sits a kernel built for responsiveness, a system that is multithreaded throughout, and a BFS file system whose indexed metadata lets Tracker, the file manager, run database-style queries across a drive.

Software installs are handled via packages that mount into the system, and earlier states are kept for rolling back botched updates.

A good pick if you are looking for a uniform desktop experience.

ReactOS

ReactOS comes with a warning label attached because the OS is still considered alpha-level software, and the download page promises nothing about stability, the safety of your files, or whether it would work on your hardware.

Behind the warning is a full operating system with a Windows-style desktop that the project says was written from scratch, while most of its user-mode code is based on Wine, the ubiquitous compatibility layer.

By default, it installs only onto a FAT16 or FAT32 partition, and Btrfs support is experimental.

A good pick if you want to see how far an open source Windows reimplementation can go.

FreeDOS

If you have old DOS games, legacy business software, or a BIOS flashing tool that won’t run anywhere else, FreeDOS is the one to grab. It’s a complete MS-DOS compatible operating system, started by Jim Hall in 1994 and still maintained today.

It runs on everything from an original 8086 to a modern PC, though newer machines need legacy BIOS mode or UEFI with legacy boot turned on. The requirements are tiny too: 640 KB of RAM and about 20 MB of disk space for a basic install.

You get a Live CD, a USB installer for real hardware, a Legacy CD, and even a floppy edition. I’d start with the Live CD in a virtual machine, which is also what the project recommends for most people.

A good pick if you want to run DOS games and legacy software on real hardware.

KolibriOS

KolibriOS is an operating system small enough to fit on a floppy disk. Which sounds weird because no modern computer comes with floppy disk anymore. Even CD drive are rare these days.

But then, the KolibriOS is not meant for modern computers anyway. You need just an i586 processor, 12 MB of RAM, and a few megabytes of disk space. It doesn’t follow POSIX either, so don’t expect to port your Unix tools over.

The kernel and drivers are written entirely in FASM assembly, which is why it boots to a GUI in seconds and opens apps almost instantly.

Despite its tiny size, you get a text editor, an image viewer, a graphics editor, a web browser, and over 30 games. It fully supports FAT12/16/32 and can read NTFS, exFAT, and ext2/3/4 partitions.

The project is still very active, so worth considering it in your retro tool kit.

A good pick if you are into retro computing or if you want to keep the 90s computer alive.

A suggestion

Try these operating systems in a virtual machine before switching. I say that because it’s a good habit to test out such non-standard pieces of kit before committing to them on your hardware.

First see what works for you. Then see if your workflow and usage habits align with what the OS offers. Once you settle on one, keep it updated so you never miss critical patches.

Air-gapped setups are better protected from such risks, of course.