在使用ubuntu系统的时候经常需要在线安装某些软件（apt-get install），然后由于国内一些原因，部分软件源无法使用，在此就需要更换软件源，具体做法如下：
1、打开软件源配置文件/etc/apt/sources.list
sudo gedit /etc/apt/sources.list
2、将文件里面的内容替换
deb http://mirrors.aliyun.com/ubuntu/ vivid main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ vivid-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ vivid-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ vivid-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ vivid-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ vivid main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ vivid-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ vivid-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ vivid-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ vivid-backports main restricted universe multiverse
上面的内容表示使用阿里的软件源，同时也有一些163的软件源也挺常用，在此粘贴如下：
deb http://mirrors.163.com/ubuntu/ precise main universe restricted multiverse deb-src http://mirrors.163.com/ubuntu/ precise main universe restricted multiverse deb http://mirrors.163.com/ubuntu/ precise-security universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-security universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-updates universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-proposed universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-proposed universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-updates universe main multiverse restricted
3、执行更新
sudo apt-get update