yum源自定义优先级，提高下载速速！

01、Install Yum Priorities

1. Run the Yum Priorities install command
   yum install yum-priorities

02、Configure Yum Priorities

1. Open the Yum Priorities configuration file
   /etc/yum/pluginconf.d/priorities.conf
   1. Ensure the following lines exist
      [main]
      enabled=1
   2. Save and close the file
2. Open the CentOS base repository configuration file
   /etc/yum.repos.d/CentOS-Base.repo
1. Add the following text to the end of the Base, Updates, Addons, and Extras repository entries*
   priority=1           #优先级高于2，越小优先级越高
2. Add the following text to the end of the CentOSPlus repository entry*
   priority=2

借鉴：http://cnzhx.net/blog/yum-priorities/