方法：
1、修改源地址：cp /etc/apt/sources.list /etc/apt/sources.list.bakvim /etc/apt/sources.list
加入如下内容（中科大的）：
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricteddeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricteddeb http://mirrors.ustc.edu.cn/ubuntu/ precise universedeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise universedeb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates universedeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates universedeb http://mirrors.ustc.edu.cn/ubuntu/ precise multiversedeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise multiversedeb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiversedeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiversedeb http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiversedeb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu precise-security main restricteddeb-src http://security.ubuntu.com/ubuntu precise-security main restricteddeb http://security.ubuntu.com/ubuntu precise-security universedeb-src http://security.ubuntu.com/ubuntu precise-security universedeb http://security.ubuntu.com/ubuntu precise-security multiversedeb-src http://security.ubuntu.com/ubuntu precise-security multiverse比较快的源：
搜狐源：deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricteddeb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricteddeb http://mirrors.sohu.com/ubuntu/ precise universedeb-src http://mirrors.sohu.com/ubuntu/ precise universedeb http://mirrors.sohu.com/ubuntu/ precise-updates universedeb-src http://mirrors.sohu.com/ubuntu/ precise-updates universedeb http://mirrors.sohu.com/ubuntu/ precise multiversedeb-src http://mirrors.sohu.com/ubuntu/ precise multiversedeb http://mirrors.sohu.com/ubuntu/ precise-updates multiversedeb-src http://mirrors.sohu.com/ubuntu/ precise-updates multiversedeb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiversedeb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse
网易源：
deb http://mirrors.163.com/ubuntu/ precise-updates main restricteddeb-src http://mirrors.163.com/ubuntu/ precise-updates main restricteddeb http://mirrors.163.com/ubuntu/ precise universedeb-src http://mirrors.163.com/ubuntu/ precise universedeb http://mirrors.163.com/ubuntu/ precise-updates universedeb-src http://mirrors.163.com/ubuntu/ precise-updates universedeb http://mirrors.163.com/ubuntu/ precise multiversedeb-src http://mirrors.163.com/ubuntu/ precise multiversedeb http://mirrors.163.com/ubuntu/ precise-updates multiversedeb-src http://mirrors.163.com/ubuntu/ precise-updates multiversedeb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse
更新看看速度：
sudo apt-get updatesudo apt-get upgrade
