添加國內源有個好處，比如下載軟件時直接時國內的服務器，速度有保證。
以下是操作方法：
1、備份
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
2、編輯
sudo gedit /etc/apt/sources.list
提示：可以使用vi、vim這些
3、覆蓋源文件的所有內容
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted deb-src http://archive.ubuntu.com/ubuntu xenial main restricted
#Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted multiverse universe
#Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted multiverse universe
#Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial universe deb http://mirrors.aliyun.com/ubuntu/ xenial-updates universe deb http://mirrors.aliyun.com/ubuntu/ xenial multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
#Added by software-properties deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted multiverse universe
#Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-security universe deb http://mirrors.aliyun.com/ubuntu/ xenial-security multiverse
4、更新
#升級軟件列表
sudo apt-get update
#系統將現有的Package升級,如果有相依性的問題，而此相依性需要安裝其它新的Package或影響到其它Package的相依性時，此Package就不會被升級，會保留下來。
#還有種說法時更新軟件，但是會更新系統內核，大版本不變，不完全可靠的消息，沒經過測試
sudo apt-get upgrade
#可以聰明的解決相依性的問題，如果有相依性問題，需要安裝/移除新的Package，就會試着去安裝/移除它。會識別出當依賴關系改變的情形並作出處理，而upgrade對此情形不處理。
sudo apt-get dist-upgrade
提示：通常更新源之后只需要升級軟件列表即可。其余兩項小心使用。
163源：
可以嘗試以下163的源，可能會意想不到的的快。
deb http://mirrors.163.com/ubuntu/ wily main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ wily-security main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ wily-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ wily-proposed main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ wily-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ wily main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ wily-security main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ wily-updates main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ wily-proposed main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ wily-backports main restricted universe multiverse
參考：
http://mirrors.aliyun.com/（更多源參考阿里雲官方提供的源列表）
http://mirrors.163.com/（更多源參考163官方提供的源列表）
http://blog.csdn.net/paincupid/article/details/52895676