deb http://mirrors.aliyun.com/ubuntu/ xenial main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main multiverse restricted universe
網上應該可以找到很多關於ubuntu源的設置方法，但是如果不搞清楚就隨便設置的話，不僅不能起到應有的效果，還會由於一些問題導致apt不可用。
最正確的更換源的方法應該如系統提示的：
a.) add 'apt_preserve_sources_list: true' to /etc/cloud/cloud.cfg
or do the same in user-data
b.) add sources in /etc/apt/sources.list.d
c.) make changes to template file /etc/cloud/templates/sources.list.tmpl
這種方法有點沒弄明白在/etc/apt/sources.list.d應該添加的是什么內容，如果是源文件的話，最后更改的模板又是什么作用？也沒有去嘗試，有時間會解決一下。
以下提供設置阿里源的方法，其他源也可以如法炮制：
-
首先查看自己的ubuntu系統的codename，這一步很重要，直接導致你更新的源是否對你的系統起效果，查看方法：
lsb_release -a
如，我的系統顯示：
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.2 LTS
Release: 14.04
Codename: trusty
顯示了一些ubuntu的版本信息，需要得到的是Codename，比如，我這里是trusty
-
確認阿里源支持：
登陸以下網頁：http://mirrors.aliyun.com/ubuntu/dists/
該網頁顯示了阿里雲支持的ubuntu系統下各個Codename版本，確保自己的Codename在該網頁中存在（一般都會有的）
-
備份系統源：
cd /etc/apt
sudo mv sources.list sources.list_bak -
添加新的源文件：
sudo vi sources.list
並添加以下內容：注意，每一行的trusty應該用第一步查看得到的Codename來代替
deb http://mirrors.aliyun.com/ubuntu/ trusty main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main multiverse restricted universe
-
保存並且sudo apt-get update，更新成功
-
以下提供配置腳本：
復制代碼
1 Codename=$( (lsb_release -a)|awk '{print $2}'|tail -n 1 )
2 echo "
3 deb http://mirrors.aliyun.com/ubuntu/ $Codename main multiverse restricted universe
4 deb http://mirrors.aliyun.com/ubuntu/ $Codename-backports main multiverse restricted universe
5 deb http://mirrors.aliyun.com/ubuntu/ $Codename-proposed main multiverse restricted universe
6 deb http://mirrors.aliyun.com/ubuntu/ $Codename-security main multiverse restricted universe
7 deb http://mirrors.aliyun.com/ubuntu/ $Codename-updates main multiverse restricted universe
8 deb-src http://mirrors.aliyun.com/ubuntu/ $Codename main multiverse restricted universe
9 deb-src http://mirrors.aliyun.com/ubuntu/ $Codename-backports main multiverse restricted universe
10 deb-src http://mirrors.aliyun.com/ubuntu/ $Codename-proposed main multiverse restricted universe
11 deb-src http://mirrors.aliyun.com/ubuntu/ $Codename-security main multiverse restricted universe
12 deb-src http://mirrors.aliyun.com/ubuntu/ $Codename-updates main multiverse restricted universe ">sources.list
13 apt-get update
復制代碼
sudo運行該腳本即可（注意運行之前最好備份之前的sources.list）