1.删除原Debian源：rm /etc/apt/sources.list 按Y再enter。（注意：此操作会删除本地DVD的源，若想保留建议使用vi /etc/apt/sources.list 再采取代码替换的方式修改源）
2.建立新的源文件:
vi
/etc/apt/sources.list
代码：
deb http://mirrors.163.com/debian squeeze main non-free contrib
deb http://mirrors.163.com/debian squeeze-proposed-updates main contrib non-free
deb http://mirrors.163.com/debian-security squeeze/updates main contrib non-free
deb-src http://mirrors.163.com/debian squeeze main non-free contrib
deb-src http://mirrors.163.com/debian-security squeeze/updates main contrib non-free
deb http://security.debian.org/ squeeze/updates main contrib
deb-src http://security.debian.org/ squeeze/updates main contrib
3.修改完毕