Usage: 

docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-
docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

Copy files/folders between a container and the local filesystem

Options:
-a, –archive Archive mode (copy all uid/gid information)
-L, –follow-link Always follow symbol link in SRC_PATH
–help Print usage

推荐http://xiaorui.cc/2015/04/12/docker%E5%AE%B9%E5%99%A8%E5%92%8C%E4%B8%BB%E6%9C%BA%E5%A6%82%E4%BD%95%E4%BA%92%E7%9B%B8%E6%8B%B7%E8%B4%9D%E4%BC%A0%E8%BE%93%E6%96%87%E4%BB%B6/