速度还行的更新源，保存在这备用
先备份原来的更新源文件：
sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
编辑更新源：
sudo gedit /etc/apt/sources.list
将里面的全部内容替换为：
deb http://ubuntu.srt.cn/ubuntu/ lucid main universe restricted multiverse
deb-src http://ubuntu.srt.cn/ubuntu/ lucid main universe restricted multiverse
deb http://ubuntu.srt.cn/ubuntu/ lucid-security universe main multiverse restricted
deb-src http://ubuntu.srt.cn/ubuntu/ lucid-security universe main multiverse restricted
deb http://ubuntu.srt.cn/ubuntu/ lucid-updates universe main multiverse restricted
deb http://ubuntu.srt.cn/ubuntu/ lucid-proposed universe main multiverse restricted
deb-src http://ubuntu.srt.cn/ubuntu/ lucid-proposed universe main multiverse restricted
deb http://ubuntu.srt.cn/ubuntu/ lucid-backports universe main multiverse restricted
deb-src http://ubuntu.srt.cn/ubuntu/ lucid-backports universe main multiverse restricted
deb-src http://ubuntu.srt.cn/ubuntu/ lucid-updates universe main multiverse restricted
更新源信息：
sudo apt-get update
如果要全面更新系统，请使用下面的命令：
sudo apt-get upgrade
From:http://www.cnblogs.com/heaad/archive/2010/05/02/1725860.html