借鉴网址：
https://blog.csdn.net/q290994/article/details/80577711
https://blog.csdn.net/qq_24326765/article/details/81953579
1、备份
cp /etc/apt/sources.list /etc/apt/sources.list.bak
2、修改
gedit /etc/apt/sources.list
3、更改源
我用的是更换为中科大源
将如下代码粘贴
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
4、生效：
sudo apt-get update
5、 好像不行，
修改dns:
sudo gedit /etc/resolvconf/resolv.conf.d/base（这个文件默认是空的）
在里面插入：
nameserver 8.8.8.8
如果有多个DNS就一行一个
修改好保存，然后使其生效
sudo resolvconf -u
测试：sudo apt-get update 可行
ubuntu 14.04 apt-get update 域名无法解析
原文：https://www.cnblogs.com/rjjhyj/p/11753262.html
