private RegionServerStartupResponse.Builder createConfigurationSubset() {
    RegionServerStartupResponse.Builder resp =
      addConfig(RegionServerStartupResponse.newBuilder(), HConstants.HBASE_DIR);
    resp = addConfig(resp, "fs.defaultFS");
    return addConfig(resp, "hbase.master.info.port");
  }
@return Subset of configuration to pass initializing regionservers: e.g. the filesystem to use
        and root directory to use.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java