build NixOS qcow image for serial testing

build-qcow2.nix

# stolen from https://gist.github.com/tarnacious/f9674436fff0efeb4bb6585c79a3b9ff
{ config, lib, pkgs, ... }:

with lib;

{
  imports =
    [
      <nixpkgs/nixos/modules/installer/cd-dvd/channel.nix>
      ./configuration.nix
    ];

  system.build.qcow2 = import <nixpkgs/nixos/lib/make-disk-image.nix> {
    inherit lib config;
    pkgs = import <nixpkgs> { inherit (pkgs) system; }; # ensure we use the regular qemu-kvm package
    diskSize = 8192;
    format = "qcow2";
    configFile = pkgs.writeText "configuration.nix"
      ''
        {
          imports = [ <./machine-config.nix> ];
        }
      '';
  };
}

configuration.nix

{ config, pkgs, ... }:
{
  imports =
    [
       <nixpkgs/nixos/modules/profiles/qemu-guest.nix>
    ];

    boot.loader.grub.enable = true;
    boot.loader.grub.version = 2;
    boot.loader.grub.device = "/dev/vda";
    boot.kernelPackages = pkgs.linuxPackages_latest;
    boot.loader.timeout = 30;

    fileSystems."/" = {
      device = "/dev/disk/by-label/nixos";
      fsType = "ext4";
      autoResize = true;
    };

    boot.loader.grub.extraConfig = ''
      serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
      terminal_input --append serial
      terminal_output --append serial
    '';

    boot.kernelParams = [ "console=ttyS0,115200" ];

    networking.hostName = "console-kaputt-vm";

    networking.useDHCP = false;
    networking.useNetworkd = false;
    networking.interfaces.enp1s0.useDHCP = true;

    i18n.defaultLocale = "en_US.UTF-8";
    console = {
      font = "Lat2-Terminus16";
      keyMap = "de";
    };

    time.timeZone = "Europe/Berlin";

    environment.systemPackages = with pkgs; [
      vim
      w3m
      wget
    ];

    programs.less.enable = true;
    programs.ssh.startAgent = true;
    programs.vim.defaultEditor = true;

    services.openssh.enable = true;

    sound.enable = false;
    hardware.pulseaudio.enable = false;

    users.users.jane = {
      isNormalUser = true;
      extraGroups = [ "wheel" ];
      initialPassword = "supersecret";
    };

    system.stateVersion = "20.03";
  }