We've been using 18.04 LTS server as our hypervisor for some time with good success. All of our production guests were created on this server, and are also all Ubuntu systems. We've recently built a new 20.04 LTS server to replace the original as our main host. We created a couple of new test guests on the new server, and everything works fine. Our problem is getting the guests from the original 18.04 server to run on the new one. The two servers don't have shared storage, so we performed off-line migrations of the guests. When we try to import the disk images into the new server and fire them up, none of them will boot. They all go immediately to grub rescue mode. We've tried all of the rescue techniques that we could find on-line, but none have worked. As a test, we tried the same off-line migration of the guests in question to another non-production 18.04 test server that we have in our lab. After importing the disk images into that box, they all started up just fine. Do we need to prep the guests that were created on the 18.04 server before running them on the new 20.04 box, or is there some other steps that we're missing to accomplish this type of migration? We've tried searching our problem, but can't find anything that references this particular issue. Any help that can be provided would be greatly appreciated. Thank you.
