johanot

let
  p = builtins.fetchTarball "https://github.com/NixOS/nixpkgs/archive/nixos-20.09.tar.gz";
  common = { pkgs, ... }: {
    fileSystems."/" = { device = "/dev/null"; fsType = "ext4"; };
    boot.loader.grub.devices = ["/dev/null"];
    environment.systemPackages = [pkgs.ngrok];
  };
in
{

johanot

let
  p = builtins.fetchTarball "https://github.com/NixOS/nixpkgs/archive/nixos-20.03.tar.gz";
  common = { pkgs, config, ... }: {
    fileSystems."/" = { device = "/dev/null"; fsType = "ext4"; };
    boot.loader.grub.devices = ["/dev/null"];
    environment.systemPackages = [pkgs.ngrok];

    nixpkgs.pkgs = import p { # set pkgs globally, kind of the same way as "network.pkgs" does transiently
      config.allowUnfree = true;
    };