Ubuntu14.04更新源
一、备份源文件
备份并替换/etc/apt/sources.list的源内容：
二、更改源文件内容
sudo gedit /etc/apt/sources.list
deb http://debian.ustc.edu.cn/ubuntu/ trusty main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-backports main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-proposed main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-security main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-updates main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-backports main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-proposed main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-security main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-updates main multiverse restricted universe
替换后执行命令： sudo apt-get update
Ubuntu 16.04 更新源
①Ctrl+Alt t 进入终端 (跟windows cmd 类似)
②cd /etc/apt
(进入源文件目录)
③sudo cp sources.list sources.list.bak (备份源文件，就是将sources.list备份为sources.list.bak）
④sudo gedit /etc/apt/sources.list
⑤复制，粘贴阿里源进来
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-backports main restricted universe multiverse
测试版源
deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
#源码
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-backports main restricted universe multiverse
测试版源
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
Canonical 合作伙伴和附加
deb http://archive.canonical.com/ubuntu/ xenial partner
deb http://extras.ubuntu.com/ubuntu/ xenial main
⑥保存
⑦更新源和软件
sudo apt-get update 更新源
sudo apt-get upgrade 更新软件
（会有提示，按Y就可以了）
