nano /etc/apt/sources.list
deb https://mirrors.sjtug.sjtu.edu.cn/debian stretch main non-free contrib
deb-src https://mirrors.sjtug.sjtu.edu.cn/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 https://mirrors.sjtug.sjtu.edu.cn/debian stretch-updates main non-free contrib
deb-src https://mirrors.sjtug.sjtu.edu.cn/debian stretch-updates main non-free contrib
deb https://mirrors.sjtug.sjtu.edu.cn/debian stretch-backports main non-free contrib
deb-src https://mirrors.sjtug.sjtu.edu.cn/debian stretch-backports main non-free contrib
nano /etc/apt/sources.list.d/pve-install-repo.list
#deb http://download.proxmox.wiki/debian/pve stretch pve-no-subscription
deb https://mirrors.ustc.edu.cn/proxmox/debian/pve buster pve-no-subscription