public Configuration getValidDefaultConfig() {
    Configuration config = getDefaultConfig();
    UnitUpdater.updateUnits(config, this);
    return config;
  }
@return default configuration of the stack, with some updates necessary so that the config can be applied
(eg. some properties need a unit to be appended)
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/Stack.java