// Async — when source or transforms may be asynchronous
// block: Wait for space (unbounded pending queue)
。关于这个话题，Line官方版本下载提供了深入分析
BBC Radio 2 has named Stirling as this year's location for its flagship live music festival.
lowerdir is the read-only directory (composefs) containing file metadata, and datadir is the directory containing the data (erofs).