simple-nixos-fediverse/installer.nix

/**
  Convert a NixOS configuration to one for a minimal installer ISO

  WARNING: Running this installer will format the target disk!
*/

{ nixpkgs,
  hostKeys ? {}
}:
machine:

let
  inherit (builtins) concatStringsSep attrValues mapAttrs;

  installer = { config, pkgs, lib, ... }:
    let
      bootstrap = pkgs.writeShellApplication {
        name = "bootstrap";
        runtimeInputs = with pkgs; [ nixos-install-tools ];
        text = ''
          ${machine.config.system.build.diskoScript}
          nixos-install --no-root-password --no-channel-copy --system ${machine.config.system.build.toplevel}
          ${
            concatStringsSep "\n" (
              attrValues (
              mapAttrs
                (kind: keys: ''
                   cp ${keys.private} /mnt/etc/ssh/ssh_host_${kind}_key
                   chmod 600 /mnt/etc/ssh/ssh_host_${kind}_key
                   cp ${keys.public} /mnt/etc/ssh/ssh_host_${kind}_key.pub
                   chmod 644 /mnt/etc/ssh/ssh_host_${kind}_key.pub
                 '')
                hostKeys
              )
            )
          }
          poweroff
        '';
      };
    in
      {
        imports = [
          "${nixpkgs}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
        ];
        nixpkgs.hostPlatform = "x86_64-linux";
        services.getty.autologinUser = lib.mkForce "root";
        programs.bash.loginShellInit = nixpkgs.lib.getExe bootstrap;

        isoImage = {
          compressImage = false;
          squashfsCompression = "lz4";
          isoName = lib.mkForce "installer.iso";
          ## ^^ FIXME: Use a more interesting name or keep the default name and
          ## use `isoImage.isoName` in the tests.
        };
      };
in
(nixpkgs.lib.nixosSystem { modules = [installer]; }).config.system.build.isoImage