I messed up my Proxmox 8 to 9 upgrade and now my server won't boot at all. The bios doesn't detect a bootable drive and reboots into the bios settings. Let me explain my f#ckup. I was upgrading from within the Proxmox web UI Shell (yes, dumb). Of course, halfway during the upgrade the web UI lost its connection and it probably got stuck upgrading on some question to overwrite file differences. I ran Putty to login and I killed the apt upgrade. After that I tried to fix the upgrade by doing
So... I created a bootable USB drive from the latest PVE ISO, booted that, from the menu choose Advanced and tried booting Rescue mode. That failed too with the following message.

I have two questions.
1. How do I boot into rescue mode (if required at all)?
2. How to get my server to boot normally again?
dpkg --configure -a. The output seemed fine but after rebooting the server it never came back. I guess the Grub boot loader is screwed.So... I created a bootable USB drive from the latest PVE ISO, booted that, from the menu choose Advanced and tried booting Rescue mode. That failed too with the following message.

I have two questions.
1. How do I boot into rescue mode (if required at all)?
2. How to get my server to boot normally again?