ubuntu 安装docker

1. sudo apt-get install docker.io
2. sudo systemctl start docker 当执行该命令时，如果提示如下错误，请根据解决方式安装：
   System has not been booted with systemd as init system (PID 1). Can't operate.
   解决方式：
   a. sudo apt-get install apt-transport-https ca-certificates curl software-properties-common
   b. curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
   c. sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
   d. sudo apt-get update
   e. sudo apt-get install docker-ce
   f. docker --version 执行到这里，如果返回的是版本号，说明docker 已成功安装，则以下步骤就无需继续执行
3. sudo systemctl enable docker
4. sudo addgroup --system docker
5. sudo adduser $USER docker
6. newgrp docker

参考：
资料一
资料二
docker文档