anchor.diff:  
       users.users.root.initialPassword = "foobar";
   
  -    # Enable the serial console on ttyS0
  -    systemd.services."serial-getty@ttyS0".enable = true;
  +    # Enable the serial console on tty1
  +    systemd.services."serial-getty@tty1".enable = true;
   
       # Force getting the hostname from Openstack metadata.
       networking.hostName = mkDefault "";
  
positive.code:     ../profiles/qemu-guest.nix
  
      # Note: While we do use the headless profile, we also explicitly
      # turn on the serial console on ttyS0 below.
      ../profiles/headless.nix
  
      # The Openstack Metadata service exposes data on an EC2 API also.
  
negative.code:     };
  
      boot.growPartition = true;
      boot.kernelParams = [ "console=tty1" ];
      boot.loader.grub.device = if (!cfg.efi) then "/dev/vda" else "nodev";
      boot.loader.grub.efiSupport = cfg.efi;
      boot.loader.grub.efiInstallAsRemovable = cfg.efi;
      boot.loader.timeout = 1;
      boot.loader.grub.extraConfig = ''
        serial --unit=1 --speed=115200 --word=8 --parity=no --stop=1
        terminal_output console serial
        terminal_input console serial
      '';
  