yum install yum-plugin-priorities.noarch
cat /etc/yum/pluginconf.d/priorities.conf
[main]
enabled = 1
cat CentOS-Media.repo
[c7-media]
name=CentOS-$releasever - Media
baseurl=file:///media/cdrom/
gpgcheck=0
enabled=1
priority=1
#priority 数字越小优先级越高
原文：https://www.cnblogs.com/xiadongzhi/p/9129937.html