ZilchOS Core

Try

Download an image from releases, qemu-system-x86_64 -cdrom ZilchOS-core-*.iso.

-nographic can be specified to pop up no windows and use a serial port instead, press Control-a followed by an x to quit.

The coolest thing to do from there is, probably, nix build -j1 github:ZilchOS/core.
That requires a ton of space and CPU though, qemu-system-x86_64 -machine q35,accel=kvm -cpu host -smp 16 -m 16G -cdrom ZilchOS-core-*.iso, maybe?

What

An minimal viable Linux distribution based on Nix, musl, clang and busybox. (well, not yet, but give it a bit of time).

Bootstrapped from a single TinyCC binary.

Why

Ever wanted to see how to put Nix derivations together into something bootable? Or get rid of /bin/sh or /etc, or break up nixpkgs into a gazillion flakes, but found one of the largest Linux distros a bit too large for such experimenting?

Yeah, maybe not, but here's a toy Nix-based OS to play with anyway.

Goals

• offer just musl, clang, busybox, Nix and Linux
• target only one platform: x86_64 QEMU
• be lean enough to experiment on
• avoid GNU software where possible (build-time dependencies of the 5 key packages are allowed, but not as runtime dependencies; the current situation is particularly bad in the bootloader area)
• force t184256 to learn more Nix-lang and nixpkgs idioms
• give content-addressed Nix a spin
• have a decent bootstrap seed/path
• have fun

Non-goals (Core)

• competing with NixOS
• going beyond a Live CD
• systemd
• any software, basically
• flexibility (other than just being small)
• portability
• configurability
• stability
• usability
• practicality

Stretch goals

• become something like Nix pills, but for building an OS
• become a stepping stone to a tad richer distro (like, one with systemd or gasp git)

Reproducibility

Reproducibility is deeply cared about, but it's a constant struggle and one cannot foresee everything.

Derivations are checked to built to the same hashes when built in three different ways:

• nix=nixos are just builds using Nix from a relatively recent NixOS unstable. Verification is done with .maint/tools/hashes.
• nix=bootstrap are builds make with Nix built during bootstrap-from-tcc's stage3. They don't use sandboxing and run in a peculiar environment. See helpers/maint/build-custom-stage5 in bootstrap-from-tcc. The used commit of bootstrap-from-tcc is the one from flake.lock.
• nix=zilchos are builds done inside a ZilchOS Core VM using its own Nix. Verification is also done with .maint/tools/hashes.

I try to build on different machines and note down the results in git notes. Commits require a specific (but adjustable) amount of successful nix, bootstrap and zilchos builds before getting into the main branch.