anchor.diff:          chmod a+x .
           chmod a+w $build $build/script.std{out,err} $build/hosts/*
   
  -        ${ztail}/bin/ztail -i 1 \
  -          -bh "${padName "OUT"} " $build/script.stdout \
  -          -bh "${padName "ERR"} " -c red $build/script.stderr \
  -          ${concatStringsSep " " (
  -            concatMap (n: map (f: ''-bh "${padName n} " "$build/hosts/${n}/${f}"'') [
  -              "console.log" "journal.log"
  -            ]) instNames
  -          )} &
  -
           ${pkgs.libvirt}/bin/virsh -c "${cfg.connectionURI}" \
  -          "${virshCmds}" >/dev/null || exit 1
  -
  -        sleep 3 # try to let ztail finish
  +          "${virshCmds}" >/dev/null &
  +        virshpid=$!
  +
  +        ${concatStrings (mapAttrsToList (n: f: ''
  +          prettytail "${padName n}" "$build/${f}" &
  +        '') cfg.tailFiles)}
  +
  +        wait $virshpid || exit 1
   
           mkdir $out
           cp -r build/* $out/
   
           ${cfg.extraBuildSteps}
  -
  -        cleanup
         '';
       };
   
  
positive.code:   instList = concatMapStringsSep "," (n: ''"${n}"'') instNames;
  
    padName = n:
      if any (n': stringLength n' > stringLength n) instNames
      then padName "${n} " else n;
  
    virshCmds = concatStringsSep ";" (flatten [
  
negative.code: let
  
    cfg = config.libvirt.test;
  
    inherit (import ../lib.nix) hexByteToInt mkMAC;
  
  