Bug#1101326: grub-common: Cannot switch back from UEFI to Legacy Mode

[Pascal Hambourg]

On 25/03/2025 at 21:07, Hartmut Krüger wrote:
> Hello,
> Thank you for the prompt reply. I followed your advice and ran
> grub-install /dev/sdb . This re-established automatic booting. However,
> I don't understand the fix. Why does Grub2 work in legacy mode on an HDD
> but not on an SSD?

GRUB works on either disk as long as the BIOS boots from that disk 
(manually with the SSD, automatically with the HDD). Here, it seems that 
the BIOS automatically tries to boot from the HDD for whatever reason. 
Did you check the disk order in the BIOS legacy boot settings ?

> Am 25.03.25 um 20:11 schrieb Pascal Hambourg:
>> The BIOS is probably trying to boot from the wrong disk.
>>
>> You can install GRUB on the hard disk, let the machine boot
>> automatically and, if it shows the GRUB menu, enter grub shell and
>> check the output of 'ls'. If it shows hd0 (the boot disk) with one
>> partition and hd1 with 5 partitions, then it means that it booted from
>> the hard disk.

Did you check this ?