国内常用的ubuntu20.04更新源有清华、网易、阿里云

sudo vim /etc/apt/sources.list

阿里

deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal main restricted universe
multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe
multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-security main restricted
universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe
multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe
multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe
multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted
universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe
multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted
universe multiverse

清华

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

中国科技大学 

deb https://mirrors.ustc.edu.cn/ubuntu/ focal main restricted universe
multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal main restricted universe
multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-updates main restricted universe
multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-updates main restricted
universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-backports main restricted universe
multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-backports main restricted
universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-security main restricted universe
multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-security main restricted
universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-proposed main restricted universe
multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-proposed main restricted
universe multiverse

网易

deb http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse

sudo apt update