what do you think about my Unix-like operating system?
Pureunix running on my macbook thru QEMU
I’ve been quietly working on a hobby operating system called PureUNIX for the past few months, mostly as a way to learn how Unix-like systems actually work under the hood.
This week I finally hit a milestone that felt worth sharing.
The latest version now has a real Unix-style process model with protected user mode, per-process virtual address spaces, fork(), exec(), and waitpid(). Seeing a process fork, replace itself with a new ELF image, and return control to the shell was one of those “okay, this actually feels like an operating system now” moments.
A few other things it has at the moment:
- EXT2 + FAT16 through a VFS
- Interactive shell with pipes and redirection
- A small vim-like editor
- User accounts and login
- Around 215 regression tests covering everything from the VFS and permissions to symlink loops, large files, and process management (currently all passing)
It’s written almost entirely in C99 with a bit of x86 assembly and targets 32-bit x86. I know it’s still missing plenty of things—preemptive scheduling, networking, mmap(), and lots more—but getting to this point has been a ton of fun.
I’m posting here because I’d genuinely love feedback from people who know Unix well. If you see something that’s particularly Unix-like, or something that makes you think “that’s not how Unix would do it,” I’d love to hear it. Those discussions are honestly the most valuable part of building a project like this.
