anchor.diff:    stage1Dir = "lib/rkt/stage1-images";
   
   in stdenv.mkDerivation rec {
  -  version = "1.19.0";
  +  version = "1.20.0";
     name = "rkt-${version}";
     BUILDDIR="build-${name}";
   
  
positive.code:       owner = "coreos";
        repo = "rkt";
        rev = "v${version}";
        sha256 = "0s3x27m16jl7nw63zg8g522km1zkwwgafrs8l8sc7pfryhnpmvag";
    };
  
    stage1BaseImage = fetchurl {
      url = "http://alpha.release.core-os.net/amd64-usr/${coreosImageRelease}/coreos_production_pxe_image.cpio.gz";
      sha256 = "1j75ad1g217aqar84m9ycl2m71g821hq9yahl4bgjaipx9xnj23g";
    };
  
    buildInputs = [
  
negative.code: let
    # Always get the information from
    # https://github.com/coreos/rkt/blob/v${VERSION}/stage1/usr_from_coreos/coreos-common.mk
    coreosImageRelease = "1235.0.0";
    coreosImageSystemdVersion = "231";
  
    # TODO: track https://github.com/coreos/rkt/issues/1758 to allow "host" flavor.
  