1、卸载旧docker
sudo yum remove docker docker-client docker-client-latest docker-common docker-latest docker-latest-logrotate docker-logrotate docker-engine
2、安装所需的软件包
sudo yum install -y yum-utils device-mapper-persistent-data lvm2
3、设置稳定的仓库
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
4、安装docker
sudo yum install docker-ce docker-ce-cli containerd.io
安装过程有一些提示，按 y 确认。
如果报错：Problem: package docker-ce-3:19.03.4-3.el7.x86_64 requires containerd.io >= 1.2.2-3 那就先装新版的 containerd.io
dnf install https://download.docker.com/linux/centos/7/x86_64/stable/Packages/containerd.io-1.2.6-3.3.el7.x86_64.rpm
5、启动docker
sudo systemctl start docker
6、hello-world测试是否成功
sudo docker run hello-world