/etc/apt/sources.list
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
1.1 修改配置文件
sudo vim /etc/apt/sources.list
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
sudo apt-get update