anchor.diff:    instList = concatMapStringsSep "," (n: ''"${n}"'') instNames;
   
     padName = n:
  -    if any (n': stringLength n' > stringLength n) instNames
  +    if any (n': stringLength n' > stringLength n) (attrNames cfg.tailFiles)
       then padName "${n} " else n;
   
     virshCmds = concatStringsSep ";" (flatten [
  
positive.code:         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
  
          mkdir $out
          cp -r build/* $out/
  
          ${cfg.extraBuildSteps}
  
          cleanup
        '';
      };
  
  
negative.code: let
  
    cfg = config.libvirt.test;
  
    inherit (import ../lib.nix) hexByteToInt mkMAC;
  
  