code: protected static void adjustMetaDirectoryNames(Configuration conf, String serviceKey) {
      adjustMetaDirectoryName(conf, DFS_NAMENODE_NAME_DIR_KEY, serviceKey);
      adjustMetaDirectoryName(conf, DFS_NAMENODE_EDITS_DIR_KEY, serviceKey);
      adjustMetaDirectoryName(conf, DFS_NAMENODE_CHECKPOINT_DIR_KEY, serviceKey);
      adjustMetaDirectoryName(
          conf, DFS_NAMENODE_CHECKPOINT_EDITS_DIR_KEY, serviceKey);
    }
docs: Append service name to each meta directory name
  
  @param conf configuration of NameNode
  @param serviceKey the non-empty name of the name node service