deb http://mirrors.ustc.edu.cn/debian/ bullseye main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian/ bullseye main contrib non-free

deb http://mirrors.ustc.edu.cn/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian/ bullseye-updates main contrib non-free

deb http://mirrors.ustc.edu.cn/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian/ bullseye-backports main contrib non-free

deb http://mirrors.ustc.edu.cn/debian-security bullseye-security main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian-security bullseye-security main contrib non-free