更新源方法：
1. 打开终端。单击主菜单中的“应用程序 - 附件 - 终端”。
2. 修改更新服务器列表。请在终端中执行下面的两条命令：
sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
还原更新源：
sudo cp /etc/apt/sources.list_backup /etc/apt/sources.list
#备份原来的软件列表，会要求输入密码
sudo gedit /etc/apt/sources.list
#用gedit打开sources.list文件
在接下来在打开的文本编辑器中，把看到的内容全部删掉，在上面Ubuntu11.04源列表里选择一组对于你来说速度最快的更新服务器列表。粘贴到你所看到的窗口中。这里推荐台湾源和网易源，更新软件的速度很快！
4. 关闭文本编辑器。
5. 更新软件包列表。执行下面的命令：
sudo apt-get update
6. 安装系统更新
打开“系统->系统管理->更新管理器”，安装更新。完成后若系统提示重新启动，请重新启动系统。
如果你是校园网用户，请查看：
下面是Ubuntu 11.04一些常见的源
#Ubuntu官方源
deb http://cn.archive.Ubuntu.com/ubuntu/ natty multiverse
deb-src http://cn.archive.Ubuntu.com/ubuntu/ natty multiverse
deb http://cn.archive.Ubuntu.com/ubuntu/ natty-updates multiverse
deb-src http://cn.archive.Ubuntu.com/ubuntu/ natty-updates multiverse
deb http://security.Ubuntu.com/ubuntu natty-security main restricted
deb-src http://security.Ubuntu.com/ubuntu natty-security main restricted
deb http://security.Ubuntu.com/ubuntu natty-security universe
deb-src http://security.Ubuntu.com/ubuntu natty-security universe
deb http://security.Ubuntu.com/ubuntu natty-security multiverse
deb-src http://security.Ubuntu.com/ubuntu natty-security multiverse
deb http://archive.canonical.com/Ubuntu natty partner
deb-src http://archive.canonical.com/Ubuntu natty partner
#Ubuntu 11.04台湾源（推荐）
deb http://tw.archive.Ubuntu.com/ubuntu/ natty main universe restricted multiverse
deb-src http://tw.archive.Ubuntu.com/ubuntu/ natty main universe restricted multiverse
deb http://tw.archive.Ubuntu.com/ubuntu/ natty-security universe main multiverse restricted
deb-src http://tw.archive.Ubuntu.com/ubuntu/ natty-security universe main multiverse restricted
deb http://tw.archive.Ubuntu.com/ubuntu/ natty-updates universe main multiverse restricted
deb-src http://tw.archive.Ubuntu.com/ubuntu/ natty-updates universe main multiverse restricted
#SRT Sources
deb http://Ubuntu.srt.cn/ubuntu/ natty main restricted universe multiverse
deb http://Ubuntu.srt.cn/ubuntu/ natty-security main restricted universe multiverse
deb http://Ubuntu.srt.cn/ubuntu/ natty-updates main restricted universe multiverse
deb http://Ubuntu.srt.cn/ubuntu/ natty-proposed main restricted universe multiverse
deb http://Ubuntu.srt.cn/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty main restricted universe multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-security main restricted universe multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-backports main restricted universe multiverse
#Ubuntu11.04网易源（速度很快、推荐）
deb http://mirrors.163.com/Ubuntu/ natty main universe restricted multiverse
deb-src http://mirrors.163.com/Ubuntu/ natty main universe restricted multiverse
deb http://mirrors.163.com/Ubuntu/ natty-security universe main multiverse restricted
deb-src http://mirrors.163.com/Ubuntu/ natty-security universe main multiverse restricted
deb http://mirrors.163.com/Ubuntu/ natty-updates universe main multiverse restricted
deb http://mirrors.163.com/Ubuntu/ natty-proposed universe main multiverse restricted
deb-src http://mirrors.163.com/Ubuntu/ natty-proposed universe main multiverse restricted
deb http://mirrors.163.com/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirrors.163.com/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirrors.163.com/Ubuntu/ natty-updates universe main multiverse restricted
#Ubuntu11.04上海源
deb http://mirror.rootguide.org/Ubuntu/ natty main universe restricted multiverse
deb-src http://mirror.rootguide.org/Ubuntu/ natty main universe restricted multiverse
deb http://mirror.rootguide.org/Ubuntu/ natty-security universe main multiverse restricted
deb-src http://mirror.rootguide.org/Ubuntu/ natty-security universe main multiverse restricted
deb http://mirror.rootguide.org/Ubuntu/ natty-updates universe main multiverse restricted
deb http://mirror.rootguide.org/Ubuntu/ natty-proposed universe main multiverse restricted
deb-src http://mirror.rootguide.org/Ubuntu/ natty-proposed universe main multiverse restricted
deb http://mirror.rootguide.org/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirror.rootguide.org/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirror.rootguide.org/Ubuntu/ natty-updates universe main multiverse restricted
#Ubuntu 11.04 搜狐源
deb http://mirrors.shlug.org/Ubuntu/ natty main universe restricted multiverse
deb-src http://mirrors.shlug.org/Ubuntu/ natty main universe restricted multiverse
deb http://mirrors.shlug.org/Ubuntu/ natty-security universe main multiverse restricted
deb-src http://mirrors.shlug.org/Ubuntu/ natty-security universe main multiverse restricted
deb http://mirrors.shlug.org/Ubuntu/ natty-updates universe main multiverse restricted
deb http://mirrors.shlug.org/Ubuntu/ natty-proposed universe main multiverse restricted
deb-src http://mirrors.shlug.org/Ubuntu/ natty-proposed universe main multiverse restricted
deb http://mirrors.shlug.org/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirrors.shlug.org/Ubuntu/ natty-backports universe main multiverse restricted
deb-src http://mirrors.shlug.org/Ubuntu/ natty-updates universe main multiverse restricted
#Ubuntu 11.04 骨头源 （bones7456架设的一个Ubuntu源 ，提供ubuntu,deepin）
deb http://Ubuntu.srt.cn/ubuntu/ natty main universe restricted multiverse
deb-src http://Ubuntu.srt.cn/ubuntu/ natty main universe restricted multiverse
deb http://Ubuntu.srt.cn/ubuntu/ natty-security universe main multiverse restricted
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-security universe main multiverse restricted
deb http://Ubuntu.srt.cn/ubuntu/ natty-updates universe main multiverse restricted
deb http://Ubuntu.srt.cn/ubuntu/ natty-proposed universe main multiverse restricted
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-proposed universe main multiverse restricted
deb http://Ubuntu.srt.cn/ubuntu/ natty-backports universe main multiverse restricted
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-backports universe main multiverse restricted
deb-src http://Ubuntu.srt.cn/ubuntu/ natty-updates universe main multiverse restricted
| 以下是ubuntu 10.10 教育网的源: sudo gedit /etc/apt/sources.list
#成都电子科大的源，教育网推荐 deb http://Ubuntu.uestc.edu.cn/ubuntu/ natty main restricted universe multiverse deb http://Ubuntu.uestc.edu.cn/ubuntu/ natty-backports main restricted universe multiverse deb http://Ubuntu.uestc.edu.cn/ubuntu/ natty-proposed main restricted universe multiverse deb http://Ubuntu.uestc.edu.cn/ubuntu/ natty-security main restricted universe multiverse deb http://Ubuntu.uestc.edu.cn/ubuntu/ natty-updates main restricted universe multiverse deb-src http://Ubuntu.uestc.edu.cn/ubuntu/ natty main restricted universe multiverse deb-src http://Ubuntu.uestc.edu.cn/ubuntu/ natty-backports main restricted universe multiverse deb-src http://Ubuntu.uestc.edu.cn/ubuntu/ natty-proposed main restricted universe multiverse deb-src http://Ubuntu.uestc.edu.cn/ubuntu/ natty-security main restricted universe multiverse deb-src http://Ubuntu.uestc.edu.cn/ubuntu/ natty-updates main restricted universe multiverse
#中科大的源，教育网推荐 deb http://debian.ustc.edu.cn/Ubuntu/ natty main restricted universe multiverse deb http://debian.ustc.edu.cn/Ubuntu/ natty-backports restricted universe multiverse deb http://debian.ustc.edu.cn/Ubuntu/ natty-proposed main restricted universe multiverse deb http://debian.ustc.edu.cn/Ubuntu/ natty-security main restricted universe multiverse deb http://debian.ustc.edu.cn/Ubuntu/ natty-updates main restricted universe multiverse deb-src http://debian.ustc.edu.cn/Ubuntu/ natty main restricted universe multiverse deb-src http://debian.ustc.edu.cn/Ubuntu/ natty-backports main restricted universe multiverse deb-src http://debian.ustc.edu.cn/Ubuntu/ natty-proposed main restricted universe multiverse deb-src http://debian.ustc.edu.cn/Ubuntu/ natty-security main restricted universe multiverse deb-src http://debian.ustc.edu.cn/Ubuntu/ natty-updates main restricted universe multiverse
#北京交大的源，教育网 deb http://mirror.bjtu.edu.cn/Ubuntu/ natty main multiverse restricted universe deb http://mirror.bjtu.edu.cn/Ubuntu/ natty-backports main multiverse restricted universe deb http://mirror.bjtu.edu.cn/Ubuntu/ natty-proposed main multiverse restricted universe deb http://mirror.bjtu.edu.cn/Ubuntu/ natty-security main multiverse restricted universe deb http://mirror.bjtu.edu.cn/Ubuntu/ natty-updates main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/Ubuntu/ natty main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/Ubuntu/ natty-backports main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/Ubuntu/ natty-proposed main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/Ubuntu/ natty-security main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/Ubuntu/ natty-updates main multiverse restricted universe
#兰州大学的源，教育网 deb ftp://mirror.lzu.edu.cn/Ubuntu/ natty main multiverse restricted universe deb ftp://mirror.lzu.edu.cn/Ubuntu/ natty-backports main multiverse restricted universe deb ftp://mirror.lzu.edu.cn/Ubuntu/ natty-proposed main multiverse restricted universe deb ftp://mirror.lzu.edu.cn/Ubuntu/ natty-security main multiverse restricted universe deb ftp://mirror.lzu.edu.cn/Ubuntu/ natty-updates main multiverse restricted universe deb ftp://mirror.lzu.edu.cn/Ubuntu-cn/ natty main multiverse restricted universe
#上海交大的源 deb http://ftp.sjtu.edu.cn/Ubuntu/ natty main multiverse restricted universe deb http://ftp.sjtu.edu.cn/Ubuntu/ natty-backports main multiverse restricted universe deb http://ftp.sjtu.edu.cn/Ubuntu/ natty-proposed main multiverse restricted universe deb http://ftp.sjtu.edu.cn/Ubuntu/ natty-security main multiverse restricted universe deb http://ftp.sjtu.edu.cn/Ubuntu/ natty-updates main multiverse restricted universe deb http://ftp.sjtu.edu.cn/Ubuntu-cn/ natty main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/Ubuntu/ natty main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/Ubuntu/ natty-backports main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/Ubuntu/ natty-proposed main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/Ubuntu/ natty-security main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/Ubuntu/ natty-updates main multiverse restricted universe
#163的，电信教育网通用 deb http://mirrors.163.com/Ubuntu/ natty main restricted universe multiverse deb http://mirrors.163.com/Ubuntu/ natty-security main restricted universe multiverse deb http://mirrors.163.com/Ubuntu/ natty-updates main restricted universe multiverse deb http://mirrors.163.com/Ubuntu/ natty-proposed main restricted universe multiverse deb http://mirrors.163.com/Ubuntu/ natty-backports main restricted universe multiverse deb-src http://mirrors.163.com/Ubuntu/ natty main restricted universe multiverse deb-src http://mirrors.163.com/Ubuntu/ natty-security main restricted universe multiverse deb-src http://mirrors.163.com/Ubuntu/ natty-updates main restricted universe multiverse deb-src http://mirrors.163.com/Ubuntu/ natty-proposed main restricted universe multiverse deb-src http://mirrors.163.com/Ubuntu/ natty-backports main restricted universe multivers |
在虚拟机中，可能会发生 NODATA错误，这是网路没有授权导致的，我的解决方法是：
把 虚拟机的网络模式设置为 NET，（一开始是桥接），这样网卡就被授权，从而可以下载数据
http://www.cnblogs.com/ggjucheng/archive/2012/08/19/2646007.html，这篇博客解释了三种
连接模式的区别。