Headaches with Grub, as usual
 

My old nemesis is back. The single most dreadful piece of software to ever plague the Linux landscape: Grub (not legacy).

Note that gdisk produces the exact same output for sda and sdb, except number and size of partitions. Grub installed on sda. What in the Grub Hell is going on?

Well, if your disks are GPT then you have no MBR for grub to install on, because GPT does not use MBR it is GPT, not MBR. If you have a UEFI boot, then you need to follow the instructions to install UEFI grub. Which in this case you must have UEFI because you stated exact same output for sda and sdb. Look into UEFI grub and how to install and manage it.

I do not do UEFI, or I'd probably have more info for you, but this should be enough to get you on the right track.

How come the same grub installed on sda, also GPT, also with a protective MBR?

that's a new on one me, found this, with a little searching on that subject.
https://unix.stackexchange.com/quest...ybrid-mbr-disk

Grub needs extra room between the mbr and first partition to install everything, this extra space exist on mdos disk but not on a gpt disk. On a gpt disk create an empty 1mb partition flagged as bios-grub for legacy install of grub. I think this might work without a bios-grub partition to make fit in mbr of gpt but not sure

which I don't have on sda, where grub installs fine.

And people complain about systemd...

probably this helps: https://blog.hostonnet.com/grub-inst...nt-be-possible

I'm just going by what research I have done on the subject.

This would indicate the op is booting in legacy mode. Is it possible the op is mixing legacy and efi on the same system, windows installed in efi mode and debian installed in legacy mode, hence forth the problem. If your booting in legacy mode /sys/firmware/efi won't exit.

If debian is install in legacy mode and assuming debian is 64bit, one way would be to boot installation disk in efi mode, run fdisk -l or parted -l to determine efi partition
mount system partition to /mnt
create /mnt/boot/efi
mount efi partition to /mnt/boot/efi
then If this works then after booting into system install grub-efi and add entry for efi partition in fstab

without installation disk, boot into debian, run fdisk -l or parted -l to determine efi partition
you will get error about efivars or something similar.
reboot, at restart use esc/f-keys to get boot options, you should have one for debian.

If your able to boot into debian efi mode,
mount efi partition to /boot/efi run grub-install
Create an entry in fstab to mount efi partition to /boot/efi

I use EFI. Debian only, no other OS. I never chose to boot in legacy mode. Why does it happen?

I used to have the 'grub-pc' package, still have 'grub-pc-bin.' I removed grub-pc and intalled grub-efi, grub-efi-amd64, and grub-efi-amd64-bin.

What does "determine" mean exactly? Do you mean I need to know my partition table or actually create that efi partition?

to find out what type of partition table you have. GPT,MBR, or other.

You need a fat32 formatted esp flagged partition about 200-300mb to boot in uefi mode. If this is a system with windows 10 preinstalled it probably already exist. If this is an empty drive you will need to create one.

Again, Windows is not involved at all in any of this. I never had Windows installed in any of these disks. Please stop mentioning Windows.

I don't have a FAT32 formatted ESP flagged partition about 200-300MB to boot in UEFI mode in the other hard disk. How did Grub ever get installed in it? I have /boot as ext2 in a 200MB partition. Would that fit the purpose?

If I have to sacrifice 200-300MB of my hard disk just so I can do something as unbelievably basic as BOOTING, then I'll just ditch this horrible POS and look for boot loaders that won't impose ridiculous demands.

This doesn't have anything to do with grub. It is an efi thingy. Your system may have had legacy mode enabled and switched to legacy automatically. With out info on you drive setup it is all a guessing game.

Hi,

I've just seen this thread.. Sorry, must disagree.. IMHO Grub2 is the best, most versatile bootloader available. It's very powerful when used properly.

All of the advice given above is totally correct. It would appear that the OP is attempting to use the Grub tools in a "non-standard" way.
The initial error messages are purely a report on why grub-install cannot perform the requested action. i.e. the drive is either not an MBR drive or doesn't have any allocated space for a bios boot partition.

I've seen machines with GPT drives (UEFI firmware, legacy mode disabled) where a legacy installation succeeds. Some tools then reported an MBR installation and others a UEFI one.
The machine seemed to run reasonably O.K. but an examination of the partition structures showed "a real mess". I advised the owner to backup his user files and start from scratch. Create a GPT drive and reinstall.

I've also seen a couple of UEFI machines that had pre-formatted MBR drives used (without creating GPT drives). Installation succeeded but drive performance was poor. Again, reinstalling with GPT solved this.

I think that poor UEFI firmware is behind most of these problems.. Just my 10p worth...

Bodge99