为什么要设置源，我一直不是很清楚。猜想一下是不是像Windows下载更新一样？希望了解的朋友给我解释一下。
不管了，先把它设置好再说。
1 首先备份源列表
sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
2 而后用gedit或其他编辑器打开
sudo gedit /etc/apt/sources.list
3 将里面的东西全部删掉，加入适合的源，保存编辑好的文件。（因为我自己是电信的宽带，所以选择电信的服务器。还有要注意你的源和你自己的Ubuntu版本号一定要对应）
＃CN99
deb http://ubuntu.cn99.com/ubuntu/ hardy main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-backports main restricted universe multiverse
＃台湾大学
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-updates main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-backports main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-security main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-proposed main restricted universe multiverse
＃台湾官方源
deb http://tw.archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse
＃韩国
deb http://ftp.daum.net/ubuntu/ hardy main restricted universe multiverse
deb http://ftp.daum.net/ubuntu/ hardy-security main restricted universe multiverse
deb http://ftp.daum.net/ubuntu/ hardy-updates main restricted universe multiverse
deb http://ftp.daum.net/ubuntu/ hardy-proposed main restricted universe multiverse
deb http://ftp.daum.net/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://ftp.daum.net/ubuntu/ hardy main restricted universe multiverse
deb-src http://ftp.daum.net/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://ftp.daum.net/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://ftp.daum.net/ubuntu/ hardy-proposed main restricted universe multiverse
deb-src http://ftp.daum.net/ubuntu/ hardy-backports main restricted universe multiverse
4 然后，刷新(一定要做，别忘了哦)
sudo apt-get update
