如何更改源：
可以在软件更新中选择源
使用如下命令更改(修改前先备份):
sudo vim /etc/apt/source.list
东北大学
deb-src http://mirror.neu.edu.cn/ubuntu/ xenial main restricted #Added by software-propertiesdeb http://mirror.neu.edu.cn/ubuntu/ xenial main restricteddeb-src http://mirror.neu.edu.cn/ubuntu/ xenial restricted multiverse universe #Added by software-propertiesdeb http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricteddeb-src http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-propertiesdeb http://mirror.neu.edu.cn/ubuntu/ xenial universedeb http://mirror.neu.edu.cn/ubuntu/ xenial-updates universedeb http://mirror.neu.edu.cn/ubuntu/ xenial multiversedeb http://mirror.neu.edu.cn/ubuntu/ xenial-updates multiversedeb http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiversedeb-src http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-propertiesdeb http://archive.canonical.com/ubuntu xenial partnerdeb-src http://archive.canonical.com/ubuntu xenial partnerdeb http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricteddeb-src http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricted multiverse universe #Added by software-propertiesdeb http://mirror.neu.edu.cn/ubuntu/ xenial-security universedeb http://mirror.neu.edu.cn/ubuntu/ xenial-security multiverse
清华大学
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricteddeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricteddeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricteddeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiversedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiversedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiversedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricteddeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universedeb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse
阿里云
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricteddeb-src http://archive.ubuntu.com/ubuntu xenial main restricted #Added by software-propertiesdeb http://mirrors.aliyun.com/ubuntu/ xenial main restricteddeb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted multiverse universe #Added by software-propertiesdeb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricteddeb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-propertiesdeb http://mirrors.aliyun.com/ubuntu/ xenial universedeb http://mirrors.aliyun.com/ubuntu/ xenial-updates universedeb http://mirrors.aliyun.com/ubuntu/ xenial multiversedeb http://mirrors.aliyun.com/ubuntu/ xenial-updates multiversedeb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-propertiesdeb http://archive.canonical.com/ubuntu xenial partnerdeb-src http://archive.canonical.com/ubuntu xenial partnerdeb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricteddeb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted multiverse universe #Added by software-propertiesdeb http://mirrors.aliyun.com/ubuntu/ xenial-security universedeb http://mirrors.aliyun.com/ubuntu/ xenial-security multiverse