手动修改方式：

163源

deb http://mirrors.163.com/ubuntu/ precise main restricted

 deb-src http://mirrors.163.com/ubuntu/ precise main restricted

 deb http://mirrors.163.com/ubuntu/ precise-updates main restricted

 deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted

 deb http://mirrors.163.com/ubuntu/ precise universe

 deb-src http://mirrors.163.com/ubuntu/ precise universe

 deb http://mirrors.163.com/ubuntu/ precise-updates universe

 deb-src http://mirrors.163.com/ubuntu/ precise-updates universe

 deb http://mirrors.163.com/ubuntu/ precise multiverse

 deb-src http://mirrors.163.com/ubuntu/ precise multiverse

 deb http://mirrors.163.com/ubuntu/ precise-updates multiverse

 deb-src http://mirrors.163.com/ubuntu/ precise-updates multiverse

 deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse

 deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse

 deb http://mirrors.163.com/ubuntu/ precise-security main restricted

 deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted

 deb http://mirrors.163.com/ubuntu/ precise-security universe

 deb-src http://mirrors.163.com/ubuntu/ precise-security universe

 deb http://mirrors.163.com/ubuntu/ precise-security multiverse

 deb-src http://mirrors.163.com/ubuntu/ precise-security multiverse

 deb http://extras.ubuntu.com/ubuntu precise main

 deb-src http://extras.ubuntu.com/ubuntu precise main

sohu源

deb http://mirrors.sohu.com/ubuntu/ precise main restricted

 deb-src http://mirrors.sohu.com/ubuntu/ precise main restricted

 deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricted

 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricted

 deb http://mirrors.sohu.com/ubuntu/ precise universe

 deb-src http://mirrors.sohu.com/ubuntu/ precise universe

 deb http://mirrors.sohu.com/ubuntu/ precise-updates universe

 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates universe

 deb http://mirrors.sohu.com/ubuntu/ precise multiverse

 deb-src http://mirrors.sohu.com/ubuntu/ precise multiverse

 deb http://mirrors.sohu.com/ubuntu/ precise-updates multiverse

 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates multiverse

 deb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse

 deb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse

 deb http://mirrors.sohu.com/ubuntu/ precise-security main restricted

 deb-src http://mirrors.sohu.com/ubuntu/ precise-security main restricted

 deb http://mirrors.sohu.com/ubuntu/ precise-security universe

 deb-src http://mirrors.sohu.com/ubuntu/ precise-security universe

 deb http://mirrors.sohu.com/ubuntu/ precise-security multiverse

 deb-src http://mirrors.sohu.com/ubuntu/ precise-security multiverse

 deb http://extras.ubuntu.com/ubuntu precise main

 deb-src http://extras.ubuntu.com/ubuntu precise main

使用方式：

sudo gedit /etc/apt/sources.list

然后把里面的列表替换成上面的列表，保存退出即可，修改完之后最好刷新一下系统的源：

sudo apt-get update

系统修改方式：

事实上，Ubuntu 已经收录了国内大部分知名的源，所以无需上网查找。

打开软件中心 – 编辑 – 软件源 ，然后点击源的列表 – 其他站点：

然后可以自己选择一个源，建议163源，比较稳定

选中后，点击右下角的选择服务器即可！