Dusk OS – A Lightning-Fast Minimalist Operating System Based on Forth

While you read these lines, sipping your coffee, a horde of developers adds 14 million additional lines of code to Windows 11 each day, a nuclear power plant explodes every time you say thank you to ChatGPT, and your trusty old smartphone fully consumes 4 GB of RAM as soon as you want to display an animated emoji. Welcome to the world we live in.

Meanwhile, in a parallel reality (or perhaps a near future), Dusk OS allows us to run a complete system with an included C compiler in less than 6000 lines of code. This 32-bit operating system based on Forth is designed with a specific goal: to be maximally useful during a civilizational collapse, when we will no longer be able to manufacture new computers, yet many will still be around us.

Yes, you read that right; it’s an OS for the apocalypse. But before you pull out your aluminum hat, let me explain why this project is fascinating even if you don’t believe in the end of the world.

4 kilobytes is the size of the Dusk OS kernel! A minuscule kernel that, at startup, gradually builds the system from the source code. From this microscopic foundation emerges a complete environment capable of compiling C, assembling code for various architectures, and even editing text. To give you an idea, it’s exactly like building a Ferrari that runs with the contents of a Lego box.

And it’s not a toy either since Dusk OS runs on real hardware: i386, amd64, ARM, RISC-V, m68k… It is compatible with BIOS or EFI systems, can operate in WebAssembly or at native speed on “normal” OSes. It also reads and writes on FAT12/FAT16 volumes. And most importantly, it is fully self-hosted, meaning that a machine running Dusk OS has all the necessary tools to improve itself.

But the real revolution lies in its philosophy, as Dusk OS does not have users, but “operators.” The difference? It’s control! As its creator explains: “You use a phone, you use a coffee machine, you even use a car these days. But you operate a bulldozer, you operate a crane, you operate an airplane. You use Linux, you use Windows. You operate Dusk OS.”

This distinction is fundamental, as on Dusk OS, there is no problem that can leave you powerless. Sure, you could have a hardware failure that messes up your system, but at least you’ll be able to identify that failure and know with certainty that you don’t need to wait for a hypothetical software patch. That’s total control.

To achieve this radical simplicity, Dusk OS has made choices that many would consider heretical. First, there are no concurrent processes. Yes, you read that right—no preemptive multitasking. On a modern machine, this seems absurd, but think about it: how often do you really need to run multiple programs simultaneously? Especially in an apocalypse! Most of the time, when your text editor is active, your shell doesn’t need to be running. The only reason we keep these two processes alive is that the memory associated with one would be lost if we “killed” it. But that’s the fault of UNIX’s memory management.

Another heresy: memory is globally shared and there is no virtual memory mechanism. Thus, when you access a memory address in the system, it’s a direct address. For an OS that wants to be “maximally” useful to the bare-metal tinkerer, we want as few layers of indirection as possible between you and the hardware.

The C compiler of Dusk OS is probably the most impressive innovation of the project, as it has an astonishing ratio of 1400 lines of code compared to TinyCC, which is considered minimalistic with 30,000 lines.

How is this possible? Well, because Dusk “circumvents” complexity instead of confronting it. For example, TinyCC dedicates 10,000 lines just to managing file formats like ELF. Dusk, on the other hand, compiles code directly in memory to run it where it is written. It’s more constraining, but infinitely simpler.

And that’s not all! Dusk is also a virulent reaction to the “modern software stack” that its creator describes as “disgustingly complicated.” A product of the cumulative effect of a software culture that generates complexity and has had decades to build upon itself, “oozing its inscrutable pus into every nook.” The guy is intense.

The thesis is provocative but hard to refute… indeed, the more we let this culture spread, the harder it is to escape. The hardware follows meekly (and in the same spirit of unnecessary complexity), making radically new approaches increasingly out of reach… but not yet impossible.

Dusk OS possesses what its creator calls an incredible “power density.” It condenses a tremendous amount of power into a tiny package. And it’s this density that allows it to do many things that a modern stack can do, but at a fraction of the complexity cost. Thus, it serves partly as a wake-up call for developers whose usual way of developing software today is stupid and wasteful, and has been for 30 years. This stupidity and waste feed into each other and lead us to design increasingly stupid hardware to cater to increasingly stupid software. At least, that’s how the creator of Dusk sees the world.

Now for those who want to see this power in action, Dusk offers a “Tour,” a series of commands that even a novice can follow without knowing Forth. You’ll see how, in just a few lines of code, you can manipulate the system’s memory, assemble native code, compile C, draw on the screen…

For example, on a notebook with an Intel ICHn chipset, imagine that you’re reading the technical sheet when suddenly: “Oh, neat, there’s an SPI interface in there. Let’s see if it’s connected to something…” On a BSD or Linux system, if you start fiddling with its registers, you risk stepping on another process’s toes and crashing the system. Under Dusk, you could completely break the SATA controller, and you’d still be operational as long as you don’t access mass storage.

Is this approach realistic for the average user? Of course not, but Dusk doesn’t target the average user. It targets the operator, the one who is creative, close to the hardware, able to read a technical sheet.

And what if the end of the world never happens? Then great! Dusk will remain a fantastic playground for rediscovering what it truly means to program a machine.

And if it does happen, at least we will have a post-apocalyptic operating system that can run everywhere, and that’s cool! So, if you’re the type to want to understand every line of code in your system, dreaming of machines that truly obey their masters rather than the other way around, or simply curious to see how so much can be done with so little, I invite you to dive into the source code of Dusk OS available on sourcehut.