nixos-install: Ask the user to set a root password

This removes the need to have an initially empty root password.

nixos/modules/virtualisation/amazon-image.nix

@@ -160,9 +160,4 @@ with lib;
   environment.systemPackages = [ pkgs.cryptsetup ];
 
   boot.initrd.supportedFilesystems = [ "unionfs-fuse" ];
-
-  # Prevent logging in as root without a password.  This doesn't really matter,
-  # since the only PAM services that allow logging in with a null
-  # password are local ones that are inaccessible on EC2 machines.
-  security.initialRootPassword = mkDefault "!";
 }

nixos/modules/virtualisation/containers.nix

@@ -117,7 +117,6 @@ in
                   modules =
                     let extraConfig =
                       { boot.isContainer = true;
-                        security.initialRootPassword = mkDefault "!";
                         networking.hostName = mkDefault name;
                         networking.useDHCP = false;
                       };

nixos/modules/virtualisation/google-compute-image.nix

@@ -114,11 +114,6 @@ in
   # Always include cryptsetup so that NixOps can use it.
   environment.systemPackages = [ pkgs.cryptsetup ];
 
-  # Prevent logging in as root without a password.  This doesn't really matter,
-  # since the only PAM services that allow logging in with a null
-  # password are local ones that are inaccessible on Google Compute machines.
-  security.initialRootPassword = mkDefault "!";
-
   # Configure default metadata hostnames
   networking.extraHosts = ''
     169.254.169.254 metadata.google.internal metadata

nixos/modules/virtualisation/nixos-container.pl

@@ -64,7 +64,6 @@ sub writeNixOSConfig {
 with lib;
 
 { boot.isContainer = true;
-  security.initialRootPassword = mkDefault "!";
   networking.hostName = mkDefault "$containerName";
   networking.useDHCP = false;
   $extraConfig

nixos/modules/virtualisation/virtualbox-image.nix

@@ -107,9 +107,4 @@ with lib;
   boot.loader.grub.device = "/dev/sda";
 
   services.virtualbox.enable = true;
-
-  # Prevent logging in as root without a password.  For NixOps, we
-  # don't need this because the user can login via SSH, and for the
-  # demo images, there is a demo user account that can sudo to root.
-  security.initialRootPassword = mkDefault "!";
 }