修改/etc/apt/sources.list
将之前的内容屏蔽，在最后面添加
deb http://ftp.sjtu.edu.cn/debian lenny main non-free contrib
deb http://ftp.sjtu.edu.cn/debian lenny-proposed-updates main non-free contrib
deb http://ftp.sjtu.edu.cn/debian-security lenny/updates main non-free contrib
deb http://mirrors.163.com/debian squeeze main
deb http://mirrors.163.com/debian squeeze-proposed-updates main
deb http://mirrors.163.com/debian-security squeeze/updates main
保存以后，运行 apt-get update 即可
