On Sun 29 Dec 2024 at 11:26:38 (-0500), Eben King wrote: > I think I've done everything reasonable in my firmware to ensure booting by > EFI. I have: > > Storage boot option control UEFI only > Other PCI device ROM priority UEFI only > (other options for both are "Legacy only" and "Disabled")
I don't recognise that terminology. > The boot device is currently /dev/sdb which has a GPT partition table, and > its first few partitions are > > number size mount point > 1 953MB /boot > 2 2GB / > 3 10GB /usr > 11 9GB /home > 13 48GB swap > 5 953MB unmounted, filesystem="grub2 core.img", flags="bios_grub" The last partition, #5, is a BIOS Boot Partition for MBR-style booting, and is where Grub stores its core.img because there's no gap after the (protective) MBR like there is on an MBR disk. Grub uses core.efi on UEFI systems, not core.img. Try booting in UEFI mode from an installer stick to see if you can. If that's possible, then partition #5 is amply large for conversion to a FAT ESP for UEFI booting. But you have to find the right "switch" in the BIOS. > The first four are ext4. > > I do recall it was a pain to make d-i keep the GPT table not overwrite it > with an MBR one. Possibly because you had booted with MBR. I've always created my GPT partitions outside the installer on non-EFI systems, so I don't have personal experience of those difficulties. > My motherboard is a Gigabyte H170 with 32 GiB RAM and I run Debian 12.8. I > swear I ran a program that showed me EFI boot vars (if they exist) and it > showed nothing. But now I can't remember what that program was. How can I > ensure that I'm actually booted using EFI? Cheers, David.
