Lost UEFI boot entry during BIOS upgrade

Hi!

I've installed OMV6 on a HP ProDesk 600 Gen 1 using UEFI mode.

I bought a used PCIe SATA card which made the BIOS hang on POST whenever I put it into the system. I realized, my BIOS was heavily outdated (looks like the first publicly released version) and decided to upgrade it.

This seems to have wiped the UEFI entries in the BIOS somehow. OMV doesn't appear as a boot entry anymore.
As OMV is installed in UEFI mode, I can't boot it in legacy mode either.

I can boot from a grml live linux USB stick, can mount all the necessary partitions and pseudo-filesystems, and chroot into the OMV system.

From there I could run "grub-install", but that didn't fix the issue.

I tried running `grub-install --bootloader-id=openmediavault /dev/sdc` but that didn't get the entry back either.

Any ideas of how to get back into my system?

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My system currently contains a system SSD where OMV is installed and two HDDs in a RAI1 with an LVM VG on it with one LV which contains an ext4 FS with a bit of data. I have made some config changes, but not that many.

So if it's not too much hassle, it would be an option to reinstall OMV, if I can copy over the config somehow and reclaim access to the data on those disks.
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I happen to have another HP Prodesk 600 with identical hardware configuration. So another option might be to install OMV on a fresh HDD in that machine, and then just transferring the disks over from the other system. This way I will have a valid UEFI entry and maybe be able to boot back into OMV. Unless UEFI uses some GUIDs or something like that.

Regards

nomike

In case someone else has the same issue, here is how I solved it:

It was also required to bind-mount /sys/firmware/efi/efivars into the chroot environment. So here's a complete step-by-step guide which you can follow in case you're having boot issues:

1. Download a grml live image (grml is a live linux distribution specifically made for system recovery), write it to some media (USB-Thumb-Drive, CD/DVD, etc.) and boot from it. See their website for details on how to do that.
2. With the command # fdisk -l you could get a list of all disk-drives and partitions. Your system disk will typically have three partitions ("EFI SYSTEM", "Linux filesystem", and "Linux swap") on it. You could also using other parameters like the drive size or disk model to ensure it is the right disk. The disk will have a device name (e.g. /dev/sda or /dev/nvme0n1). In my case, it is /dev/sda and the partitions are numbered (/dev/sda1, /dev/sda2, /dev/sda3).
3. Mount the filesystems of your OMV installation to /mnt:
   # mount /dev/sda2 /mnt# mount /dev/sda1 /mnt/boot/efi
4. Mount the proc pseudo filesystem:
   # mount -t proc proc /mnt/proc
5. Bind mount other required filesystems:
   # mount -o bind /dev /mnt/dev# mount -o bind /sys /mnt/sys# mount -o bind /sys/firmware/efi/efivars /mnt/sys/firmware/efi/efivars# mount -o bind /dev/pts /mnt/dev/pts# mount -o bind /run /mnt/run
6. Chroot into the OMV system:
   # chroot /mnt /bin/bash
7. Inside the OMV system, you can now install grub again:
   # grub-install --bootloader-id debian /dev/sda
8. Exit out of the chroot environment by pressing ctrl+d or typing exit.
9. Once you're back in the grml shell, unmount all filesystems mounted in the prior steps:
   # umount /mnt/run# umount /mnt/dev/pts# umount /mnt/sys/firmware/efi/efivars# umount /mnt/sys# umount /mnt/dev# umount /mnt/proc# umount /mnt/boot/efi# umount /mnt/
10. Reboot the system by typing reboot, remove the grml media from the computer and you should now be able to boot back into OMV.