Docker overlay2 分层原理1

https://yuerblog.cc/2019/03/22/k8s%E9%9A%8F%E7%AC%94-overlay2%E5%AE%B9%E5%99%A8%E5%88%86%E5%B1%82%E5%8E%9F%E7%90%86/yuerblog.cc