先备份
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
再编辑
sudo nano /etc/apt/sources.list
添加国内源（可删除文件内所有源）
deb http://mirrors.163.com/debian/ buster main non-free contrib deb http://mirrors.163.com/debian/ buster-updates main non-free contrib # deb http://mirrors.163.com/debian/ buster-backports main non-free contrib deb-src http://mirrors.163.com/debian/ buster main non-free contrib # deb-src http://mirrors.163.com/debian/ buster-updates main non-free contrib deb-src http://mirrors.163.com/debian/ buster-backports main non-free contrib deb http://mirrors.163.com/debian-security/ buster/updates main non-free contrib deb-src http://mirrors.163.com/debian-security/ buster/updates main non-free contrib
最后更新
sudo apt-get update && sudo apt-get upgrade
