我的 Debian 6.0 一般使用如下的 /etc/apt/sources.list: deb http://ftp.debian.org/debian/ squeeze main non-free contrib deb http://ftp.debian.org/debian/ squeeze-updates main non-free contrib deb http://ftp.debian.org/debian/ squeeze-proposed-updates main non-free contrib deb http://security.debian.org/ squeeze/updates main non-free contrib
是否有些是不必要的?