Why would an EFI “BIOS” update break the EFI boot manager?

Question

After successfully updating my P8H67-m pro with the latest "bios" version I ended up with a blinking cursor on the top left corner of a black screen. No errors, no nothing. The bios now only listed a SATA: <disc name> boot option in place of the usual UEFI ubuntu one. I'm using a GPT partitioning scheme.

While I don't see any reason why something would change on my hdd while flashing the bios; after spending wasting a day on this, the working solution was to properly reinstall grub-efi-amd64 (here's how I did it). Until now I thought that the EFI boot manager would parse my EFI partition and come back with whichever options were available but it seems more like it need to be explicitly told about it and that it'll forget everything on update.

If it's the case it appears to me like a severe limitation. So: is this standard UEFI behavior, something specific to asus motherboards or does linux improperly install grub in the first place? Are the EFI OS loaders path infos stored on some NVRAM which get erased during a bios update? Will I face the same issue if I try to boot my hdd with another computer?

PS: the bios version isn't at fault, after the initial update i downgraded to initial version to no avail. Now that I solved the issue, I'm running the latest version just fine. It's flashing the bios, no matter to which version that breaks the system.

Answer 1

I had a similar problem after updating my BIOS and was asking myself why a complete restore of the hdd via dd would not leave me with a bootable system.

It seems that when installing the boot loader, the operating system must register an entry to the "EFI Boot Variables" inside the NVRAM. No entry, no boot. What makes this all the more confusing is that with UEFI specification 2.3 the system may look up a file EFI/boot/bootx64.efi similar to when booting from an external medium on the main hard disk, so some versions of UEFI might just boot up without fiddling around.

This registering should be done with efibootmgr but modprobe efivars fails for me as well, under ubuntu. So I also just chroot and reinstall grub-efi and hope for the best.