网易163：http://mirrors.163.com/.help/debian.html
使用方法：
echo "deb http://mirrors.163.com/debian/ stretch main non-free contrib deb http://mirrors.163.com/debian/ stretch-updates main non-free contrib deb http://mirrors.163.com/debian/ stretch-backports main non-free contrib deb-src http://mirrors.163.com/debian/ stretch main non-free contrib deb-src http://mirrors.163.com/debian/ stretch-updates main non-free contrib deb-src http://mirrors.163.com/debian/ stretch-backports main non-free contrib deb http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib deb-src http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib" > /etc/apt/sources.list