Julia Evans

My Rust OS will never be finished (and it's a success!)

In November/December last year, I spent 3 weeks working on a toy operating system in Rust. (for more, see Writing an OS in Rust in tiny steps, and more).

I wrote a ton of blog posts about it, and I gave a talk about the process at Mozilla last week (the video). At that talk, a few people asked me if I was going to finish the project. I said no, and here’s why.

There are lots of reasons for working on programming projects. Just a few:

  • to end up with useful code
  • to learn something
  • to explore a new concept (see: Bret Victor’s demos)

The reason I wrote an operating system in Rust wasn’t so that I could have an operating system written in Rust. I already have an kernel on my computer (Linux), and other people have already written Rust operating systems better than I have. Any code that I write in 3 weeks is at best a duplication of someone else’s work, and mimicking the state of the art 20 years ago.

I worked on that project to learn about how operating systems work, and that was a huge success. I read a 20-part essay about linkers, and learned about virtual memory, how executables are structured, how program execution works, how system calls work, the x86 boot process, interrupt handlers, keyboard drivers, and a ton of other things.

Another amazing example of a project like this is @kellabyte’s Haywire, a HTTP server in C she wrote to learn more about writing performant code. It actually compiles and you can benchmark it yourself, but her blog posts are more useful to me than her code – Hello haywire HTTP response caching in Haywire, Further reducing memory allocations and use of string functions in Haywire.

So when people ask me why my code doesn’t compile, it’s because the code is basically a trivial output of the process. The blog posts I wrote are much more important, because they talk about what I learned. My code probably won’t be useful to you – it would be better to start with rustboot and take your own path.

Not finishing your project doesn’t mean it’s not a success. It depends what your goals are the for the project! I wrote an operating system in Rust to learn, and I learned a ton. It’s not finished, and it won’t be. How could it ever be? I hope to not ever finish learning.