deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal main multiverse restricted universe

deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-security main multiverse restricted universe

deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-updates main multiverse restricted universe

deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-backports main multiverse restricted universe

deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal main multiverse restricted universe

deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-security main multiverse restricted universe

deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-updates main multiverse restricted universe

deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-backports main multiverse restricted universe