上海交大源
/etc/apt/sources.list
deb https://mirror.sjtu.edu.cn/ubuntu/ focal main restricted universe multiverse
# deb-src https://mirror.sjtu.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirror.sjtu.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
# deb-src https://mirror.sjtu.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirror.sjtu.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
# deb-src https://mirror.sjtu.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb https://mirror.sjtu.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# deb-src https://mirror.sjtu.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# deb https://mirror.sjtu.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# deb-src https://mirror.sjtu.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse