一句一句的执行：
yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
yum install -y yum-utils device-mapper-persistent-data lvm2
yum install -y docker-ce docker-ce-cli containerd.io
docker -v
systemctl start docker
docker ps
docker run hello-world
出现以下这句，代表docker安装成功。
Hello from Docker!
This message shows that your installation appears to be working correctly.