Recently I experienced a very frustrating bug with one of the hosts in my Proxmox cluster. It was not the first time I experienced this bug, previously I was not aware of any fix and had to re-install the system if this occurred. Fortunately there is now a fix!
What would happen is you would update your Proxmox installation and a zpool upgrade on the ‘rpool’ occurs, then you reboot, and find that your system is unbootable when you see the following error:
Error: unknown filesystem. grub rescue>
This would occur if the following points are true:
- System installed using Proxmox VE ISO 6.3 or earlier
- System uses GRUB legacy BIOS boot to boot
- System is using ZFS as the root filesystem