在CentOS 7上在线安装Docker

官方参考网站： https://docs.docker.com/install/linux/docker-ce/centos/

#下载旧的安装包
$ sudo yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-engine

$ sudo yum install -y yum-utils \
  device-mapper-persistent-data \