前言
Ubuntu自带的软件源是国外的服务器，下载速度很慢，在国内使用大都需要更换软件源。
桌面版
桌面版的源更换很简单，在设置里就能找到，换了会自己更新。
终端
在一些情况下Ubuntu是没有桌面的，只有个终端，比如在服务器上，在Windows的子系统中。
我更换的是阿里云的
- sudo vim /etc/apt/sources.list
- 删除所有文件并粘贴一下内容。
deb http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
