nixos/{demo,installer/virtualbox-demo}: drop

This is no longer referenced anywhere and so will inevitably bitrot,
and doesn’t do anything that isn’t simple to achieve with the
module documentation.

nixos/modules/installer/virtualbox-demo.nix

@@ -1,61 +0,0 @@
-{ lib, ... }:
-
-with lib;
-
-{
-  imports =
-    [ ../virtualisation/virtualbox-image.nix
-      ../installer/cd-dvd/channel.nix
-      ../profiles/demo.nix
-      ../profiles/clone-config.nix
-    ];
-
-  # FIXME: UUID detection is currently broken
-  boot.loader.grub.fsIdentifier = "provided";
-
-  # Allow mounting of shared folders.
-  users.users.demo.extraGroups = [ "vboxsf" ];
-
-  # Add some more video drivers to give X11 a shot at working in
-  # VMware and QEMU.
-  services.xserver.videoDrivers = mkOverride 40 [ "virtualbox" "vmware" "cirrus" "vesa" "modesetting" ];
-
-  powerManagement.enable = false;
-  system.stateVersion = lib.mkDefault lib.trivial.release;
-
-  installer.cloneConfigExtra = ''
-  # Let demo build as a trusted user.
-  # nix.settings.trusted-users = [ "demo" ];
-
-  # Mount a VirtualBox shared folder.
-  # This is configurable in the VirtualBox menu at
-  # Machine / Settings / Shared Folders.
-  # fileSystems."/mnt" = {
-  #   fsType = "vboxsf";
-  #   device = "nameofdevicetomount";
-  #   options = [ "rw" ];
-  # };
-
-  # By default, the NixOS VirtualBox demo image includes SDDM and Plasma.
-  # If you prefer another desktop manager or display manager, you may want
-  # to disable the default.
-  # services.xserver.desktopManager.plasma5.enable = lib.mkForce false;
-  # services.displayManager.sddm.enable = lib.mkForce false;
-
-  # Enable GDM/GNOME by uncommenting above two lines and two lines below.
-  # services.xserver.displayManager.gdm.enable = true;
-  # services.xserver.desktopManager.gnome.enable = true;
-
-  # Set your time zone.
-  # time.timeZone = "Europe/Amsterdam";
-
-  # List packages installed in system profile. To search, run:
-  # \$ nix search wget
-  # environment.systemPackages = with pkgs; [
-  #   wget vim
-  # ];
-
-  # Enable the OpenSSH daemon.
-  # services.openssh.enable = true;
-  '';
-}

nixos/modules/profiles/demo.nix

@@ -1,21 +0,0 @@
-{ ... }:
-
-{
-  imports = [ ./graphical.nix ];
-
-  users.users.demo =
-    { isNormalUser = true;
-      description = "Demo user account";
-      extraGroups = [ "wheel" ];
-      password = "demo";
-      uid = 1000;
-    };
-
-  services.displayManager = {
-    autoLogin = {
-      enable = true;
-      user = "demo";
-    };
-    sddm.autoLogin.relogin = true;
-  };
-}