Booting from Devices > 2TB with BIOS and GPT

[Michael Hierweck]

Hi all,

today I experienced GRUB 2.02 was not able to boot successfully a QEMU based virtual machine in 
BIOS mode from a GPT partitioned virtual disk when the root partition (containing /boot) 
exceeds 2 TB even when a there is a tiny bios_grub partition (ef02) exists at the beginning of 
the disk.

I was dropped to the GRUB rescue shell but was not able to load any modules: "attempt to read 
or write outside of disk 'hd0'".

I booted into a rescue system and reinstalled grub (update-grub/grub-install) without any error 
message or warning. Sadly no success.

After that I did some experiments. Reinstalled the system but assigned only 1 TB to the 
root/swap partition. The system booted successfully. After that I increased the partition to 4 
TB and increased the filesystem. GRUB was still able to boot.


I suppose the problem occurs when (after stage 1 and 1.5 have been successfully loaded) parts 
of stage 2 (modules from /boot/grub...) have to been loaded from disk sectors beyond the 2 TB 
limit.

Can you confirm that not only the bios_grub partition but also /boot/grub has to be located in 
the first 2 TB of the disk?

Thanks in advance,

Michael