1.vi /etc/apt/sources.list

2.shift+G，跳到最后一行

3.换行，加上科大源路径

deb http://debian.ustc.edu.cn/ubuntu/ natty main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ natty-backports main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ natty-proposed main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ natty-security main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ natty-updates main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ natty main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ natty-backports main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ natty-proposed main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ natty-security main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ natty-updates main multiverse restricted universe

Ubuntu Server更新源-科大源