1. 切换到 /etc/apt 目录下，备份源文件
切换路径
cd /etc/apt/
备份源文件
sudo mv sources.list sources.list.bak
2. 新建源文件
sudo vi sources.list
将以下内容粘贴进去即可
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
粘贴之后保存退出
3. 执行命令更新配置
sudo apt-get update
sudo apt-get upgrade
4. 阿里云Ubuntu镜像源文件地址
https://developer.aliyun.com/mirror/ubuntu?spm=a2c6h.13651102.0.0.3e221b11b0A3WX