UEFI bios type not detecting debian EFI bootloader in guest VM.

[chrcoluk]

So this one has me bamboozled.

I did a exotic setup in a VM mirroring one that is working fine on proxmox 7.3.

Essentially the VM is running Debian bookworm, and has a EFI bootloader on a EFI partition. When trying to boot from the VM configured to use UEFI, it will just say a vague it cannot find disk. But I then found this page.

https://record99.blogspot.com/2021/12/bdsdex-failed-to-load-boot0001-uefi-bhyve-sata-disk.html

Sure enough when I did what that blog said which is to go into the UEFI boot manager and boot from file, navigating to the EFI bootloader, the OS booted right up.

I compared the EFI partition to the working guest on proxmox 7.3 and they are an exact match in layout, size of partition and files.

/boot/efi/EFI/debian

and files

BOOTX64.CSV  fbx64.efi  grub.cfg  grubx64.efi  mmx64.efi  shimx64.efi

The problem occurs whether there is a virtual EFI disk or not, and regardless of preroll keys.

I then copied the EFI file as instructed in the blog to this path and filename.

/boot/efi/EFI/BOOT/bootx64.efi

Now it boots automatically.

Any idea whats going on here? the path of the files is where grub puts them, so seems odd I have to mnually move them and rename the file. Has the emulated UEFI bios changed or is this likely just coincidence?

 

[fschauer]

Sounds like there is no valid boot entry on the EFI disk. This can be regenerated by running grub-install in the Debian VM.

For some background:
Since there was no boot entry pointing to EFI/debian/grubx64.efi, the EFI instead checks the fallback path EFI/BOOT/bootx64.efi.

 

[chrcoluk]

Thank you, you was right.

Seems I am learning all the time, and was something about UEFI I didnt previously know and now understand why Proxmox warns about a missing EFI disk.

So the original install there was no Proxmox EFI disk, and Proxmox documentation says it makes a temporary one when it is missing.

After the install I shutdown the VM which would have wiped that temporary EFI disk, and so the Debian boot entry was lost, which meant even when I added one later it didnt fix it, until of course as you said I reinstalled the grub files, which then wrote the changes to the EFI disk.

Stupid from me, but now I understand what happened, thank you.