目前在澳门大学，Ubuntu缺省源为 ubuntu.com，速度比较慢，所以切换到香港中文大学。
sudo vim /etc/apt/sources.list在 sources.list 中增加以下内容即可。
deb http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty main restricted universe multiverse deb http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security main restricted universe multiverse deb http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-updates main restricted universe multiverse deb http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-proposed main restricted universe multiverse deb http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-backports main restricted universe multiverse deb-src http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty main restricted universe multiverse deb-src http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security main restricted universe multiverse deb-src http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-updates main restricted universe multiverse deb-src http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-proposed main restricted universe multiverse deb-src http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-backports main restricted universe multiverse然后更新的速度起飞。
