rpi cross

configuration.nix

{ config, lib, pkgs, ... }:

{
  imports = [
    <nixpkgs/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix>
  ];

  nixpkgs = {
    crossSystem.system = "armv7l-linux";
  };

  # closure minification
  environment.noXlibs = true;
  services.xserver.enable = false;
  services.xserver.desktopManager.xterm.enable = lib.mkForce false;
  
  # this pulls too much graphical stuff
  services.udisks2.enable = lib.mkForce false;
  # this pulls spidermonkey and firefox
  security.polkit.enable = false;

  boot.supportedFilesystems = lib.mkForce [ "vfat" ];
  i18n.supportedLocales = lib.mkForce [ (config.i18n.defaultLocale + "/UTF-8") ];

  documentation.enable = false;
  documentation.nixos.enable = false;
}

script.sh

export NIX_PATH=nixpkgs=/home/jane/local_nixpkgs_checkout
nix-build --cores 0 '<nixpkgs/nixos>' \
  -I nixos-config=configuration.nix \
  -A config.system.build.sdImage \
  -o result-cross \
  --keep-going

Interesting. IIRC that Aarch64 can't be used for my specific RPI hardware. It'd be nice if hydra could help us with the cross builds - see NixOS/mobile-nixos#197