开启终端，输入命令"sudo gedit /etc/apt/sources.list"
在打开的源列表，即sources.list中输入合适的更新源（输入前把列表中的内容先清空）。
常见的更新源：
#中国科学技术大学更新服务器（教育网,推荐校园网和网通用户使用）：
deb http://debian.ustc.edu.cn/ubuntu/ jaunty main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ jaunty main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe
#中国台湾大学更新服务器（推荐网通、电信用户使用，很稳定的源）：
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-updates main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-updates main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-backports main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-backports main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-security main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-security main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-proposed main multiverse restricted universe
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ jaunty-proposed main restricted universe multiverse
#上海市上海交通大学更新服务器（推荐校园网和网通用户使用）：
deb http://ftp.sjtu.edu.cn/ubuntu/ jaunty main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ jaunty main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ jaunty-backports main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ jaunty-proposed main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ jaunty-security main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ jaunty-updates main multiverse restricted universe
#北京交通大学的更新服务器（推荐校园网用户、网通用户使用）：
deb http://mirror.bjtu.edu.cn/ubuntu/ jaunty main restricted universe multiverse
deb http://mirror.bjtu.edu.cn/ubuntu/ jaunty-backports restricted universe multiverse
deb http://mirror.bjtu.edu.cn/ubuntu/ jaunty-proposed main restricted universe multiverse
deb http://mirror.bjtu.edu.cn/ubuntu/ jaunty-security main restricted universe multiverse
deb http://mirror.bjtu.edu.cn/ubuntu/ jaunty-updates main restricted universe multiverse
deb-src http://mirror.bjtu.edu.cn/ubuntu/ jaunty main restricted universe multiverse
deb-src http://mirror.bjtu.edu.cn/ubuntu/ jaunty-backports main restricted universe multiverse
deb-src http://mirror.bjtu.edu.cn/ubuntu/ jaunty-proposed main restricted universe multiverse
deb-src http://mirror.bjtu.edu.cn/ubuntu/ jaunty-security main restricted universe multiverse
deb-src http://mirror.bjtu.edu.cn/ubuntu/ jaunty-updates main restricted universe multiverse
cn99cn99.com更新服务器（江苏省常州市电信，推荐电信用户使用）：
deb http://ubuntu.cn99.com/ubuntu/ jaunty main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ jaunty-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ jaunty-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ jaunty-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ jaunty main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ jaunty-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ jaunty-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ jaunty-backports main restricted universe multiverse
根据自己的网络状况选择，一个不行可以尝试另一个。
然后执行“sudo apt-get update”进行更新。
