anchor.diff:  
   , name ? "nixos-disk-image"
   
  -, format ? "raw"
  +, # Disk image format, one of qcow2, vpc, raw.
  +  format ? "raw"
   }:
   
   with lib;
  
positive.code:   targets = map (x: x.target) contents;
  
    prepareImage = ''
      export PATH=${pkgs.lib.makeSearchPathOutput "bin" "bin" prepareImageInputs}
  
      mkdir $out
      diskImage=nixos.raw
  
negative.code:     raw   = "img";
    };
  
    nixpkgs = cleanSource pkgs.path;
  
    channelSources = pkgs.runCommand "nixos-${config.system.nixosVersion}" {} ''
      mkdir -p $out
  