[SOLVED] Issue booting into GRUB after upgrade from Proxmox 8 to 9

[Carizoeuf]

Hello,

I recently upgraded my main Proxmox node from version 8 to 9, following carefully all prerequisites and steps listed in the official guide: Upgrade from 8 to 9.

After the upgrade, upon reboot, I was dropped to the GRUB prompt (grub>), instead of the normal boot menu. Attempting ls showed my LVM volumes correctly, but insmod normal failed to load, and the menu never appeared.

To regain access, I used the manual kernel boot method: I set the root to my LVM volume, loaded the latest kernel (6.17), loaded the corresponding initramfs, and booted successfully. This allowed me to start the Proxmox node and access the system.

I have not yet performed any permanent GRUB repair. Now that I can boot, what is the recommended procedure to permanently fix GRUB after such an upgrade?

Thanks!

 

[Carizoeuf]

I have missed the 4.6.4:
https://pve.proxmox.com/wiki/Upgrade_from_8_to_9#GRUB_Might_Fail_To_Boot_From_LVM_in_UEFI_Mode

I did not see this information because I did not have any error and only the grub> prompt. A shame there is not any guide to boot in this mode, I had to do some research to find how to boot.
I will add the information here when I have access to my computer.

 

[Carizoeuf]

Proxmox VE 8 → 9 Upgrade – GRUB fails to boot on UEFI + LVM

After upgrading a Proxmox VE node from PVE 8 to PVE 9 in UEFI mode with root on LVM, the system dropped to a grub> prompt on reboot. This is a known issue.

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Temporary boot from GRUB

At the grub> prompt:

set root=(lvm/pve-root)
ls /boot
linux /boot/vmlinuz-6.17.4-1-pve root=/dev/mapper/pve-root ro quiet
initrd /boot/initrd.img-6.17.4-1-pve
boot

This boots the node successfully.

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Permanent fix

Once booted, run:

[ -d /sys/firmware/efi ] && echo "UEFI OK"

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=proxmox --recheck
update-grub
shutdown -r now

After reboot, GRUB loads normally and the node boots automatically.

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Verification

uname -r            # latest kernel
efibootmgr -v       # BootCurrent points to \EFI\proxmox\grubx64.efi
pveversion -v       # confirms PVE 9 running

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Cause: The correct GRUB package was installed, but the UEFI firmware was still booting an old/incorrect GRUB entry. grub-install ensures the fixed version is used.