寫在前面：本文摘錄自網上，經過驗證，大膽使用。
一、ubuntu16.04更換國內源
1.備份原始源文件source.list
桌面打開終端，執行命令：sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
2.修改源文件source.list
（1）終端執行命令：sudo chmod 777 /etc/apt/sources.list 更改文件權限使其可編輯；
（2）執行命令：sudo gedit /etc/apt/sources.list 打開文件進行編輯；
（3）刪除原來的文件內容，復制下面的任意一個到其中並保存（常用的是阿里源和清華源，推薦阿里源）；
阿里源：
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
3.更新
sudo apt-get update