nano /etc/apt/sources.list

deb https://mirrors.aliyun.com/debian-archive/debian stretch main contrib non-free
#deb https://mirrors.aliyun.com/debian-archive/debian stretch-proposed-updates main non-free contrib
deb https://mirrors.aliyun.com/debian-archive/debian stretch-backports main non-free contrib
deb https://mirrors.aliyun.com/debian-archive/debian-security stretch/updates main contrib non-free
deb-src https://mirrors.aliyun.com/debian-archive/debian stretch main contrib non-free
#deb-src https://mirrors.aliyun.com/debian-archive/debian stretch-proposed-updates main contrib non-free
deb-src https://mirrors.aliyun.com/debian-archive/debian stretch-backports main contrib non-free
deb-src https://mirrors.aliyun.com/debian-archive/debian-security stretch/updates main contrib non-free