查看Debian 版本
cat /etc/apt/sources.list
備份原來的源配置文件
cp /etc/apt/sources.list /etc/apt/sources.list.backup
重新編寫源配置文件vim /etc/apt/sources.list將下面複製好的內容粘貼，wq保存
#debian 9.x (stretch)
deb http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb http://mirrors.aliyun.com/debian-security stretch/updates main
deb-src http://mirrors.aliyun.com/debian-security stretch/updates main
deb http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib