anchor.diff:  
   let
     cfg = config.services.zookeeper;
  -  
  +
     zookeeperConfig = ''
       dataDir=${cfg.dataDir}
       clientPort=${toString cfg.port}
  
positive.code:       default = 1;
        type = types.int;
      };
   
      extraConf = mkOption {
        description = "Extra configuration for Zookeeper.";
        type = types.lines;
  
negative.code:         ExecStart = ''
            ${pkgs.jre}/bin/java \
              -cp "${pkgs.zookeeper}/lib/*:${pkgs.zookeeper}/${pkgs.zookeeper.name}.jar:${configDir}" \
              ${escapeShellArgs cfg.extraCmdLineOptions} \
              -Dzookeeper.datadir.autocreate=false \
              ${optionalString cfg.preferIPv4 "-Djava.net.preferIPv4Stack=true"} \
              org.apache.zookeeper.server.quorum.QuorumPeerMain \
  