1、备份原来的源

sudo cp /etc/apt/sources.list /etc/apt/sources.list.20231021

2、编辑sources.list配置文件更换源

sudo vim/etc/apt/sources.list

添加如下内容

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

3、更新源

sudo apt-get update

4、更新软件

sudo apt-get upgrade