Laser NixOS

Nix expressions for building a NixOS image for the Raspberry Pi 3 controlling the laser cutter in CCCHH.

TL;DR

export \
MACHINE=raspberry-pi-3 \
SD_CARD=/dev/sda \
NIXPKGS_REV=dba4149

nix-build -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/${NIXPKGS_REV}.tar.gz" -I machine=machines/$MACHINE --out-link out-links/$MACHINE

Building

The ISO must be built by emulation if you are not building on an aarch64 machine. Build your host NixOS with the following in the configuration.

  boot.binfmt.emulatedSystems = [
    "aarch64-linux"
  ];

Machines

Select one of the machines and set the environment variable.

export MACHINE=raspberry-pi-3

nixpkgs Versions

Select a nixpkgs version and set the enviroment variable.

export NIXPKGS_REV=dba4149

It's recommended to set it to one of the revision hashes from the table below. But you can also set it to a branch name like nixos-24.05.

ref	rev	date
nixos-24.05	dba4149	2024-11-07

Build

nix-build -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/${NIXPKGS_REV}.tar.gz" -I machine=machines/$MACHINE --out-link out-links/$MACHINE

Flashing

Select the correct block device and set the environment variable.

export SD_CARD=/dev/sda
sudo sh -c "zstd -dcf out-links/$MACHINE/sd-image/*.img.zst | dd status=progress bs=64k iflag=fullblock oflag=direct of=$SD_CARD && sync && eject $SD_CARD"

Deployment

For deploying new images without reflashing, you can use NixOps.

nix-shell -p nixops_unstable_minimal

Since stable NixOps reuqires Python2, we use the unstable version.

[nix-shell:~]$ nixops --version
NixOps 1.7-unstable-2024-02-28-pre-08feccb

Create

nixops create -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/${NIXPKGS_REV}.tar.gz" -I machine=machines/$MACHINE

Deploy

nixops deploy -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/${NIXPKGS_REV}.tar.gz" -I machine=machines/$MACHINE