How to fix Error message with ‘yum update, yum install’ “This system is not registered with an entitlement server. You can use subscription-manager to register.” ?

 1-do 

/etc/yum/pluginconf.d/subscription-manager.conf

2-Inside the “subscription-manager.conf” file

 change enabled to 0 and save the file

 enabled=0

 

3. Lastly issue the “yum clean all” command

yum clean all