修改源并更新升级Ubuntu
不同的网络状况连接以下源的速度不同，所以cn99并不一定是最快的源。建议在 添加前手动验证以下源的连接速度(ping下就行)，比如说北京网通用户连接cn99就非常慢，而ftp.sjtu.edu.cn是相对较快的源，选择最 快的源可大大节省下载时间，请根据自己网络环境设置更新服务器，以达到最快的速度。（经试验，执行下文中需要的apt-get命令或使用《新立得软件包管 理器》时，必须更改了默认的更新服务器才可以使用，否则可能找不到很多安装包，或者安装包版本低。）
注意，你可以同时加入几个源。或者将官方的源(也就是下面的Archive.ubuntu.com的条目)直接加在文件的最后，以避免出现 404 Not Found 文件未发现 的错误。
在终端执行以下命令（第一条是备份现有服务器列表，第二条是使用Gedit编辑，您也可以使用自己喜爱的编辑器编辑，如nano，kate，vim等。）
sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
sudo gedit /etc/apt/sources.list
从以下各服务器列表内容中选择一段替换文件中的所有内容（请根据自己网络环境设置更新服务器，以达到最快的速度。）
Archive.ubuntu.com 更新服务器(欧洲，此为官方源，推荐使用。)：
deb http://archive.ubuntu.com/ubuntu/ edgy main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ edgy-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ edgy-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ edgy main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ edgy-backports main restricted universe multiverse
deb http://archive.ubuntu.org.cn/ubuntu-cn/ edgy main restricted universe multiverse
Ubuntu.cn99.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/ edgy main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-backports main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu-cn/ edgy main restricted universe multiverse
Mirror.lupaworld.com 更新服务器(浙江省杭州市电信，亚洲地区官方更新服务器，推荐全国用户使用。）：
deb http://cn.archive.ubuntu.com/ubuntu edgy main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu edgy-security main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu edgy-updates main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu edgy-backports main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu edgy-proposed main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu edgy main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu edgy-security main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu edgy-updates main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu edgy-backports main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu edgy-proposed main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu/ubuntu-cn edgy main restricted universe multiverse
上海市 上海交通大学 更新服务器（教育网，推荐校园网和网通用户使用。）：
deb http://ftp.sjtu.edu.cn/ubuntu/ edgy main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-backports main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-proposed main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-security main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-updates main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-backports main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-proposed main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-security main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-updates main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu-cn/ edgy main multiverse restricted universe
北京市清华大学 更新服务器（教育网，推荐校园网和网通用户使用。)：
deb http://mirror9.net9.org/ubuntu/ edgy main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ edgy-backports main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ edgy-proposed main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ edgy-security main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ edgy-updates main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ edgy main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ edgy-backports main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ edgy-proposed main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ edgy-security main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ edgy-updates main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu-cn/ edgy main multiverse restricted universe
中国 台湾省台湾大学 更新服务器（推荐网通用户使用，电信PING平均响应速度41MS。）
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-updates main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-backports main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-security main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-proposed main multiverse restricted universe
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://ftp.sjtu.edu.cn/ubuntu-cn/ edgy main multiverse restricted universe
Mirror.vmmatrix.net 更新服务器（上海市电信，推荐电信网通用户使用。）:
deb http://mirror.vmmatrix.net/ubuntu/ edgy main restricted universe multiverse
deb-src http://mirror.vmmatrix.net/ubuntu/ edgy main restricted universe multiverse
deb http://mirror.vmmatrix.net/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://mirror.vmmatrix.net/ubuntu/ edgy-updates main restricted universe multiverse
deb http://mirror.vmmatrix.net/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://mirror.vmmatrix.net/ubuntu/ edgy-backports main restricted universe multiverse
deb http://mirror.vmmatrix.net/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://mirror.vmmatrix.net/ubuntu/ edgy-security main restricted universe multiverse
deb http://mirror.vmmatrix.net/ubuntu/ edgy-proposed main multiverse restricted universe
deb-src http://mirror.vmmatrix.net/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://ftp.sjtu.edu.cn/ubuntu-cn/ edgy main multiverse restricted universe
ubuntu.cnsite.org 更新服务器 (福建省福州市 电信):
deb http://ubuntu.cnsite.org/ubuntu/ edgy main restricted universe multiverse
deb-src http://ubuntu.cnsite.org/ubuntu/ edgy main restricted universe multiverse
deb http://ubuntu.cnsite.org/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://ubuntu.cnsite.org/ubuntu/ edgy-updates main restricted universe multiverse
deb http://ubuntu.cnsite.org/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://ubuntu.cnsite.org/ubuntu/ edgy-backports main restricted universe multiverse
deb http://ubuntu.cnsite.org/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://ubuntu.cnsite.org/ubuntu/ edgy-security main restricted universe multiverse
deb http://ubuntu.cnsite.org/ubuntu/ edgy-proposed main multiverse restricted universe
deb-src http://ubuntu.cnsite.org/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://ubuntu.cnsite.org/ubuntu-cn/ edgy main multiverse restricted universe
到以下网址可以自定义产生若干源：http://www.ubuntulinux.nl/source-o-matic 以下网址有极其全面的源，以供补充：http://italy.copybase.ch/blog/lista-repository-sourceslist-ottimizzata-per-ubuntu-kubuntu-linux/
保存编辑好的文件，执行以下命令更新。
sudo apt-get update
sudo apt-get dist-upgrade
