That happened to me as well, on an Oracle Cloud server. The kernel panicked, and so did I. I thought I was toast. But after about six or eight reboots from the cloud console, some of which were “pull-the-plug” reboots, and after about half-an-hour of waiting, the server came up long enough for me to edit grub.cfg and revert to the previous kernel.
I was able to save my instance thereby. A day later, there was another new kernel update offered, and that’s when I grew more certain my theory about kernel trouble was true. And I found the bug description to confirm it. Yeah, pretty nasty.
I devised a Stupid Grub Trick, as I call it, that I will try to find time to post anon, so one would be able to avoid such a calamity in the future.
Good luck with your restore, @RBoy. I must say this thread is giving me a queasy stomach after my own near disaster last – when was it, Wednesday?
By the way, you said you regained access to your old server. If you still have it or can get access once more – for me it took some hard reboots and some waiting – well, go in and upgrade one more time, as there is another new kernel that doesn’t have the bug. Or revert to the previous kernel.