Can anybody tell me if I can request a second cert for a domain where a letsencrypt cert is active?
My problem is that I have a linux server+apache+cert up and running but I want to try to move my web server into Docker/Kubernetes on the same machine. Kubernetes (ingress) would automatically request a new letsencrypt cert for this but I don't want to lose/invalidate the existing one. If this is not working as intended I would like to just delete the whole Kubernetes cluster and start my Apache again and the old cert should be used again.
Yes, you can. Please note the rate limits though, you can only get a certain number of duplicates within a week (currently max 5).
Please make sure your Docker/Kubernetes stores its certificates permanently and not ephemeral, as people often run into rate limits when they pull down and up and down and up again their Docker images without storing the certificates in a permanent way.
Also, when testing you should use the staging environment before getting a cert from production.