Writing an operating system kernel from scratch
24 comments
·September 14, 2025lordleft
I will never not find this kind of project incredibly impressive. It’s interesting to think that Linux, after all, is really just the kernel — and yet getting that work done paved the way to getting an open source version of Unix installed on billions of machines. Great stuff!
diath
It's even more funny and amusing when you remember that in the initial release mail for Linux, Torvals said "just a hobby, won't be big and professional like gnu".
https://groups.google.com/g/comp.os.minix/c/dlNtH7RRrGA/m/Sw...
chuckadams
He's also referred to Linux as "the GNU Emacs of all terminal emulators".
Someone
> I will never not find this kind of project incredibly impressive
I wouldn’t call it incredibly impressive. The path on how to write a minimal multi-tasking kernel has been beaten decades ago.
Writing a kernel that can boot and do a few things is ‘just’ a matter of being somewhat smart and have some perseverance. Doing it for RISC-V complicates things a bit compared to x86, but there, too, the information about initialising the hardware often is easily obtained (for example: https://wiki.osdev.org/RISC-V_Meaty_Skeleton_with_QEMU_virt_... I wouldn’t know whether this project used that)
I think the author agrees, given (FTA) that they wrote “This is a redo of an exercise I did for my undergraduate course in operating systems”
It’s work, may be nice work, but I think everybody with a degree in software engineering could do this. Yes, the OS likely will have bugs, certainly will have rough edges, but getting something that can multi-process, with processes shielded from each other by a MMU isn’t hard anymore.
flamedoge
To you maybe. The subset of population that is even interested, smart, persevering to do this is extremely tiny.
d_sem
Is there a book one can read to learn how to create one?
hollerith
It is equally valid to say that Stallman's starting to write a C compiler and Unix utilities (in 1984 whereas the Linux project started in late 1991) paved the way to getting an open source version of Unix installed on billions of machines.
kimixa
I agree - there's a number of kernels that were "open source" and released at a similar time enough time to linux (e.g. 386BSD in '92) that I could see any of those winning the "community battle" and taking that space instead, but no real credible "development toolchain" equivalent until decades later.
Though I'm unsure how differing licenses might have affected this - I suspect that really early in it's development the "copyleft" nature of the GPL Linux didn't make as much of a difference, as from what I remember most commercial uses of Linux didn't come until it had already gained significant momentum.
treyd
The copyleft nature was essential to good driver support. It set it up such that for corporations making drivers the easiest path was to get the driver upstreamed. There was a bunch of hoops they could have gone through to avoid that (as many did, like Nvidia) but that became a sorta-default.
Copyleft encourages a collaborative relationship between entities because it makes trying to play it close to the chest with IP involve more legal effort (if it's possible at all).
null
lifeline82
[dead]
WD-42
Zig really is amenable to OS development. And so is RISC-V. I started this same exercise except with x86 first. I quickly got annoyed with all the legacy boilerplate required. RISC-v doesn’t have any of that. It’s so much faster to get up and running. Here’s my bad zig: https://github.com/Fingel/aeros-v
toast0
> with x86 first. I quickly got annoyed with all the legacy boilerplate required.
IMHO, if you use a reasonable bootloader, you don't have too much boilerplate. Multiboot loaders do leave you in real mode, and most people want to be in protected mode, so you have to set up some tables and do a jump, but that's not that much boilerplate. There's a bit more stuff if you disable legacy interrupt controllers (which you probably want to) but it seems to me being able to maybe run on a regular pc is worth it (caveats about console interfaces apply... my hobby OS needs bios boot and uses some vga things that I found aren't well supported... serial console is easier, but lots of computers don't have a serial port either)
ethin
You still have to set up the GDT, TSS, all that other legacy stuff that isn't actually used but it's still there. And if you set it up incorrectly, your punished for it with triple faults and the like, even if nobody even uses anything like the GDT or TSS these days.
ktosobcy
> El acceso a la presente dirección IP ha sido bloqueado en cumplimiento de lo dispuesto en la Sentencia de 18 de diciembre de 2024, dictada por el Juzgado de lo Mercantil nº 6 de Barcelona en el marco del procedimiento ordinario (Materia mercantil art. 249.1.4)-1005/2024-H instado por la Liga Nacional de Fútbol Profesional y por Telefónica Audiovisual Digital, S.L.U. > https://www.laliga.com/noticias/nota-informativa-en-relacion...
Of FFS...
one thing is using http but another this one…
flykespice
...what? a football organization in Spain has the power to restrict internet access to the entire country?
WJW
Football is really big in Spain dontcha know?
chris_wot
How does one get their hands on low-cost RISC hardware?
Rzor
There's this $10 board on Aliexpress called Milk-V Duo S. It's been popping up on my recs every now and then. Looks interesting.
https://aliexpress.com/w/wholesale-Milk%2525252dV-Duo-S.html
Taken directly from its description:
>Milk-V Duo S is an upgraded model of Duo with an upgraded SG2000 master with a larger 512MB RAM and extended IO capability
>Onboard WI-FI6/BT5(Model Milk-V-Duo-S-512M-Basic/Milk-V-Duo-S-512M-eMMC does not have this function)
>USB 2.0 HOST port
>100 Mbps Ethernet Portwith PoE Support (via PoE HAT)
>Dual MIPI CSI with ISP
>The device also supports switch between RISC-V and ARM boot via a switch
hackerInnen
[dead]
Submitted separately by the author:
https://news.ycombinator.com/item?id=45236479
Copying their comment to here:
I have redone the classical exercise of writing a tiny OS kernel with time sharing, which manages a couple of user threads. My goal was to experiment specifically on RISC-V + OpenSBI. Additionally, I wanted to explore Zig a little bit, so that was the language used instead of the traditional C, but it should be straightforward how to do the same experiment in either C or Rust.
It's definitely very rough around the edges, and it's more of an experiment and an intro for people who want to go through step 0 of learning OS kernel development and computer architecture. Nevertheless, I hope it is still a fun experimental thing to play with over the weekend!
The full walkthrough and the GitHub link are available at the link posted!