cp /etc/apt/sources.list /etc/apt/sources.listbak #备份原有配置文件
vi /etc/apt/sources.list #编辑
注释掉本地光盘源这一行：
deb cdrom:[Debian GNU/Linux 6.0.4 _Squeeze_ - Official i386 DVD Binary-1 20120128-12:53]/ squeeze contrib main
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/ squeeze-proposed-updates main contrib non-free
deb-src http://mirrors.163.com/debian-security/ squeeze/updates main contrib non-free
deb http://ftp.sjtu.edu.cn/debian/ squeeze main non-free contrib
deb http://ftp.sjtu.edu.cn/debian/ squeeze-proposed-updates main contrib non-free
deb http://ftp.sjtu.edu.cn/debian-security/ squeeze/updates main contrib non-free
deb-src http://ftp.sjtu.edu.cn/debian/ squeeze main non-free contrib
deb-src http://ftp.sjtu.edu.cn/debian/ squeeze-proposed-updates main contrib non-free
deb-src http://ftp.sjtu.edu.cn/debian-security/ squeeze/updates main contrib non-free
apt-get update #更新源
apt-cache search ssh #查看更新的包
apt-get install openssh-server #安装ssh服务
apt-get install ssh #安装ssh