编辑文件
1vim /etc/apt/sources.list添加镜像源
1deb http://mirrors.ustc.edu.cn/debian stretch main contrib non-free
2deb http://mirrors.ustc.edu.cn/debian stretch-updates main contrib non-free
3deb http://mirrors.ustc.edu.cn/debian stretch-backports main contrib non-free
4deb http://mirrors.ustc.edu.cn/debian-security/ stretch/updates main contrib non-free更新apt
1apt-get update