I suggest you read the following:
It's not mentioned in the OL 7 admin guide, but as I recall from past discussions on the topic, Oracle guarantees full user space compatibility between the UEK kernel and the RHCK kernel, and full user space compatibility among the various UEK kernels for a particular OS release version.
What are you installing? UEK5 or UEK5R2?
Spacewalk does not run anything the kernel space or kernel ABI, not as I recall, and hence there's no reason why Spacewalk 2.7 and UEK5R2 should not be compatible, or any other kernel for the same reason.
The installation guide for Spacewalk 2.7 doesn't mention anything about the kernel either:
Thanks very much. I'm currently running Spacewalk 2.7 with OL 7.6 UEK 4. I'm looking at upgrading to UEK 5 on this server. I was wondering about any gotchas.
I'm running Spacewalk 2.7 on OL 7.6 with UEK 4. Wondering if Spacewalk 2.7 can run on and is supported on OL 7.6 UEK 5.
Fully supported. Spacewalk doesn't care what kernel you're running.