Docker CE on Ubuntu supports overlay2 and aufs storage drivers.
For Ubuntu 16.04 and higher, the Linux kernel includes support for OverlayFS, and Docker CE uses the overlay2 storage driver by default. If you need to use aufs instead, you need to configure it manually.
手动设置方法：
修改 /lib/systemd/system/docker.service
在启动命令后追加参数[红色字体]
ExecStart=/usr/bin/dockerd --storage-driver=aufs -H fd://
之后重启 docker 服务
systemctl daemon-reload && systemctl restart docker
使用 docker info 查看
官方推荐使用 overlay2