Show HN: A DOS-like hobby OS written in Rust and x86 assembly

122 krustowski 22 6/19/2025, 1:38:57 PM github.com ↗

To try it out, simply build the project yourself from source, or use attached bootable ISO image of the system (in Releases on Github) and run it in QEMU.

https://blog.vxn.dev/rou2exos-rusted-edition

Comments (22)

OhNotAPaper · 16m ago

Out of curiosity, why x86? Is it the preponderance of resources? The weird instruction format? The complexity of the boot sequence? Are you specifically trying to mimic DOS?

> A support for the ARM architecture (aarch) is coming soon too.

Wow! How do you support a DOS-like OS across multiple architectures when DOS itself is tightly tied to interactions among the program, the system code, and the architecture?

rollcat · 7h ago

Memory-safe language. x86_64, with Arm on the roadmap. Networking stack. Boots from a CD and via multiboot. Your hobby project wipes the floor with DOS.

pvg · 6h ago

Whoa there. Gotta run Doom and BASIC to compete with DOS. That is the officially recognized DOS-Kármán line.

krustowski · 5h ago

What a challenge! Need to implement some interrupts it seems then, to provide an API for filesystem and so... Thank you for such idea

rzzzt · 1h ago

Doomgeneric has a very thin platform-specific layer: https://github.com/ozkl/doomgeneric?tab=readme-ov-file#porti...

jmspring · 1h ago

I want some TSRs and print spoolers...

rollcat · 3h ago

DOOM required DOS 5.0. rou2exOS is only the second take. Watch this area ;)

jdsully · 1h ago

Nobody cares about Lotus 1-2-3 support any longer :)

jmspring · 5m ago

What about Wordstar?

mycall · 1h ago

also, can't be a dos with the 'dir' command.

krustowski · 1h ago

Afaik there is a 'DIR' command in MS-DOS. Anyway, what would be a better command to list a directory? I could think of 'ls' maybe

mixmastamyk · 1h ago

I would have preferred something like this to the current UEFI environment and shell, a FLOSS 64-bit DOS-like. A cool retro boot manager and diagnostic env perhaps.

Could this run from an efi system partition? Seems to support fat12, what about gpt?

Does it poke video hardware like DOS, or have a terminal like output?

krustowski · 54m ago

Booting from an EFI system partition has not been tested yet. FAT12 is the only filesystem (ok, there is a memdisk implementation, but it won't work now) supported, so GPT is not supported at the moment too (yet). Kinda aiming for FAT32 implementation to be the very next implemented (flash disks are usually FAT32 iirc). Not sure about the last question: the OS utilizes/directly writes to the VGA buffer in memory, the provided resolution is 80x25 by GRUB.

mixmastamyk · 21m ago

So MBR partitions? Or no partitions, like from a floppy? Or perhaps it doesn’t know because grub handles that part.

DrNosferatu · 6h ago

DOS-like but not DOS-compatible, correct?

krustowski · 6h ago

You are right. The first iteration however is 16bit and is very close to MS-DOS in terms of compatibility. Moreover, any OS that can handle simple disk I/O ops could be considered a DOS system too, innit?

leeter · 5h ago

Correct, there is a difference between MS-DOS and IBM-PC compatible and a DOS (ex: all the DOSes that existed for Amiga/Apple II/Commodore etc). There are many DOSes (and even MSDOSes, because yay early PC era incompatibilities!), but there is a very dubious list of things needed to be MS-DOS and IBM-PC compatible. You can probably do it if you're willing to setup a hypervisor and emulate some hardware.

NGL one of my long term projects was/is something exactly like this but UEFI and secure boot. The idea being to use the VM extensions to create IBM-PC and DOS compatible environments. For anything using DPMI[1] I'd probably do the same trick as Win95 did and just replace it with my own implementation so it's not too overburdened with layers.

[1] https://en.wikipedia.org/wiki/DOS_Protected_Mode_Interface

JdeBP · 2h ago

A version of (say) FreeDOS that was layered on top of the EFI API instead of PC98 firmware interrupts would be quite interesting. That would be a major architectural change to most of the programs, of course. But one would have provided the EFI Shell with essentially a complete suite of MS-DOS (albeit not PC-DOS or DR-DOS) commands. That could probably be quite easily ported to (say) ARM whereas the original still has x86isms.

On the other hand, did you see https://github.com/FlyGoat/csmwrap when it came up a few weeks ago?

* https://news.ycombinator.com/item?id=44101828

There are already projects to provide replacements for the vanished Compatibility Support Module.

leeter · 1h ago

I did see that and for people that need that specific functionality it seemed like a good solution.

My goal was more "What if DOS hadn't ended and but kept up support for modern hardware" along with emulation of common things in DOS gaming. So for example you would be able to set up a PIV that mapped certain resources directly or emulated them depending on the need.

Could I use DOSBox for this... yes, but this is a "why not" sort of thing. I figured it would be a good excuse to learn OS dev. But life has kept me busy for now.

DrNosferatu · 3h ago

...meaning MS-DOS compatible :)

I.e.: runs Alley Cat and Dune 2 - and Doom.

JdeBP · 3h ago

And prevents Lotus 1-2-3 from running? (-:

vardump · 2h ago

That's the litmus test. No version of DOS is complete until Lotus 1-2-3 no longer runs.