修改 /etc/apt/source.list為一下內容即可，並且換用了清華的源
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universe deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universe deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiverse deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiverse deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universe deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse