1 deb http://mirrors.ustc.edu.cn/debian bullseye main 2 deb-src http://mirrors.ustc.edu.cn/debian bullseye main 3 4 deb http://mirrors.ustc.edu.cn/debian-security/ bullseye-security main 5 deb-src http://mirrors.ustc.edu.cn/debian-security/ bullseye-security main 6 7 deb http://mirrors.ustc.edu.cn/debian bullseye-updates main 8 deb-src http://mirrors.ustc.edu.cn/debian bullseye-updates main