anchor.diff:        # Generate a /etc/hosts file.
         hosts = lib.concatMapStrings (m: "${m.second} ${m.first}\n") machinesWithIP;
   
  -      nodes_ = map (m: lib.nameValuePair m.first
  -          { imports = [
  -              (lib.getAttr m.first nodes)
  -              "${nixos}/modules/virtualisation/qemu-vm.nix" # !!!
  -              "${nixos}/modules/testing/test-instrumentation.nix" # !!! should only get added for automated test runs
  -            ];
  -            config =
  +      nodes_ = map (m: lib.nameValuePair m.first [
  +          { config =
                 { networking.hostName = m.first;
                   networking.interfaces =
                     [ { name = "eth1";
  
positive.code:                 services.nixosManual.enable = false; # !!!
                };
            }
          ) machinesWithIP;
  
      in lib.listToAttrs nodes_;
  
  
negative.code: 
  
    buildVM =
      nodes: configurations:
  
      import "${nixos}/lib/eval-config.nix" {
        inherit nixpkgs services system;
        modules = configurations ++ [
          "${nixos}/modules/virtualisation/qemu-vm.nix" # !!!
          "${nixos}/modules/testing/test-instrumentation.nix" # !!! should only get added for automated test runs
        ];
        extraArgs = { inherit nodes; };
        /* !!! bug in the module/option handling: this ignores the
           config from assignIPAddresses.  Too much magic. 
  