1.备份原有的源文件
cd /etc/apt/
sudo cp -p sources.list sources.list.bak
2.修改源文件
sudo vim sources.list
删除sources.list 文件中所有内容添加一下内容 保存退出。
/****************** 18.04源 *****************************************/
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
/****************** 20.04源 *****************************************/
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security multiverse
3.
sudo apt-get update
apt upgrade