anchor.diff:    installPhase = ''
       mkdir -p $out
       cp bin/ipxe.dsk bin/ipxe.usb bin/ipxe.iso bin/ipxe.lkrn bin/undionly.kpxe $out
  +
  +    # Some PXE constellations especially with dnsmasq are looking for the file with .0 ending
  +    # let's provide it as a symlink to be compatible in this case.
  +    ln -s undionly.kpxe $out/undionly.kpxe.0
     '';
   
     meta = with stdenv.lib;
  
positive.code: 
    src = fetchgit {
      url = git://git.ipxe.org/ipxe.git;
      sha256 = "11w8b0vln3skfn8r1cvzngslz12njdkwmnacyq3qffb96k2dn2ww";
      inherit rev;
    };
  
  
negative.code: { stdenv, fetchgit, perl, cdrkit, syslinux, xz, openssl }:
  
  let
    date = "20170922";
    rev = "74d90b33f8490adcee2026ece18d8411d93b6a39";
  in
  
  stdenv.mkDerivation {
  