如果想改变ubuntu中的源，使用
sudo gedit /etc/apt/sources.list  用一下源替换里边的内容
ubuntu9.10源

deb http://run.hit.edu.cn/ubuntu/ jaunty main multiverse restricted universe 
deb http://run.hit.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe 
deb http://run.hit.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe 
deb http://run.hit.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe 
deb http://run.hit.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe 
deb-src http://run.hit.edu.cn/ubuntu/ jaunty main multiverse restricted universe 
deb-src http://run.hit.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe 
deb-src http://run.hit.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe 
deb-src http://run.hit.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe 
deb-src http://run.hit.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe 

ubuntu10.04源

deb http://run.hit.edu.cn/ubuntu/ lucid main restricted universe multiverse
deb-src http://run.hit.edu.cn/ubuntu/ lucid main restricted universe multiverse
deb http://run.hit.edu.cn/ubuntu/ lucid-updates main restricted universe multiverse
deb-src http://run.hit.edu.cn/ubuntu/ lucid-updates main restricted universe multiverse
deb http://run.hit.edu.cn/ubuntu/ lucid-backports main restricted universe multiverse
deb-src http://run.hit.edu.cn/ubuntu/ lucid-backports main restricted universe multiverse
deb http://run.hit.edu.cn/ubuntu/ lucid-security main restricted universe multiverse
deb-src http://run.hit.edu.cn/ubuntu/ lucid-security main restricted universe multiverse

如果出现无法更新的情况，重启一下linux