@小鱼 qing hua yuan :

默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释

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

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

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

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

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

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

deb http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted universe multiverse

deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted universe multiverse 预发布软件源，不建议启用 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-proposed main restricted universe multiverse