1、将原始的source list复制替换
sudo cp /etc/apt/sources.list /etc/apt/sources.list.old2、使用vim打开source list
sudo vim /etc/apt/sources.list3、将source list中的内容删除，输入ggdG，然后 摁 i 开始文本输入，去清华镜像源找到对应的ubuntu系统的镜像源，将下面的内容粘贴进去即可。
#ubuntu 16.04LTS 镜像 # 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse # 预发布软件源，不建议启用 # deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
*可以使用以下代码查看ubuntu版本
cat /etc/issuse