提示：
Loading "installonlyn" plugin
Loading "rhnplugin" plugin
This system is not registered with RHN.
RHN support will be disabled.
Existing lock /var/run/yum.pid: another copy is running. Aborting.
解决办法：
rm /var/run/yum.pid
这个时候，有个提示：rm ：是否删除普通文件 “/var/run/yum.pid” ？
回车后就结束了该进程就好了。