1.安装 yum-priorities
yum install yum-priorities
2.priorities的配置文件是/etc/yum/pluginconf.d/priorities.conf，确认其是否存在。内容为：
[root@chy002 yum.repos.d]# cat !$ cat /etc/yum/pluginconf.d/priorities.conf [main] enabled = 1
3.编辑 /etc/yum.repos.d/目录下的*.repo 文件来设置优先级。参数为：
priority=N # N的值为1-99，数字越大,优先级越低
推荐的设置为：
[base], [addons], [updates], [extras] … priority=1
[centosplus],[contrib] … priority=2
Third Party Repos such as rpmforge … priority=N (where N is > 10 and based on your preference)
原文：http://www.cnblogs.com/chyuanliu/p/7834287.html