redhat 5 套间的更新问题

netbsd

我在redhat5中使用命令

#yum  update   
系统总是提示

Loading "rhnplugin" plugin
Loading "installonlyn" plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Update Process
Setting up repositories
No Repositories Available to Set Up
Reading repository metadata in from local files
No Packages marked for Update/Obsoletion

不知道这是怎么回事?

好像是那个yum的源,我没有添加, 但是好像没有找到和redhat5有关的源啊??