Centos7源的配置修改

对yum网络源的讲解

http://www.cnblogs.com/mchina/archive/2013/01/04/2842275.html

http://wuyelan.blog.51cto.com/6118147/1546674

修改为国内的aliyun 的源

http://mirrors.aliyun.com/help/centos