sudo cp /etc/apt/sources.list /etc/apt/source.list.bk
sudo vim /etc/apt/sources.list
https://lug.ustc.edu.cn/wiki/mirrors/help/ubuntu
https://mirrors.ustc.edu.cn/repogen/
sudo apt-get update
修改完保存,进行更新
sudo cp /etc/apt/sources.list /etc/apt/source.list.bk
sudo vim /etc/apt/sources.list
https://lug.ustc.edu.cn/wiki/mirrors/help/ubuntu
https://mirrors.ustc.edu.cn/repogen/
sudo apt-get update
修改完保存,进行更新