1、修改源地址：
cp /etc/apt/sources.list /etc/apt/sources.list.bak
vim /etc/apt/sources.list
修改之後要記得apt-get update
加入如下內容（中科大的）：
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted
deb http://mirrors.ustc.edu.cn/ubuntu/ precise universe
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise universe
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates universe
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates universe
deb http://mirrors.ustc.edu.cn/ubuntu/ precise multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu precise-security main restricted
deb-src http://security.ubuntu.com/ubuntu precise-security main restricted
deb http://security.ubuntu.com/ubuntu precise-security universe
deb-src http://security.ubuntu.com/ubuntu precise-security universe
deb http://security.ubuntu.com/ubuntu precise-security multiverse
deb-src http://security.ubuntu.com/ubuntu precise-security multiverse
比較快的源：
搜狐源：
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
網易源：
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