Patch RHEL Server

 #Remove wrong existing subscription

subscription-manager remove --all

subscription-manager unregister

subscription-manager clean

#register subscription

subscription-manager register

subscription-manager refresh

subscription-manager attach --auto

#Alternatively register subscription in single commandline

subscription-manager register --username <redhatlogin> --password <redhatpass> --auto-attach

#Update patches

yum clean all

yum repolist

yum update

#Update only security patches

yum clean all

yum repolist

yum update --security

rpm -qa | grep -i kernel