Go to solve the "this system is not registered with RHN" update in RedHat.

because RedHat is not registered, you cannot use its own source to update it. Therefore, you can change the source to update it.

change the yum source, that is, change/etc/yum. repos. d/RHEL-debuginfo. Repo file. Enter/etc/yum. repos. d/directory, terminal input
wget http://docs.linuxtone.org/soft/lemp/CentOS-Base.repo
you can get the CentOS-Base.repo file under this Directory, which is the source file of centos, you just need to rename it as a rhel-debuginfo.repo, a backup of the previous file.