Bug#1093820: boot ends in grub command prompt after fresh debian install

[Pascal Hambourg]

On 24/01/2025 at 09:14, M. Dietrich wrote:
>> On Wed, 22 Jan 2025 23:07:54 +0000 Pascal Hambourg wrote:
>> On 23/01/2025 at 00:07, M. Dietrich wrote:
>>
>> And not in /boot/efi/EFI/BOOT ?
>>
> no, a `find /boot/efi` would have shown (i added the ubuntu
> here manually, but that's how it was if i remember correctly):
> 
> /boot/efi/EFI/Boot
> /boot/efi/EFI/Boot/bootx64.efi
> /boot/efi/EFI/Boot/fbx64.efi
> /boot/efi/EFI/Boot/mmx64.efi

This is what I asked about, so it is actually present.
FAT is case-insensitive. This location is called "removable media path" 
because it is used to boot from removable media.

When the UEFI firmware does not or cannot use EFI boot variables to 
select the right boot loader, it tries to boot 
/boot/efi/EFI/Boot/bootx64.efi. If this one was installed by Ubuntu 
(Debian installer does not install it by default unless requested in 
expert install), then it is not surprising that it loads Ubuntu's GRUB.

> when i issue a `efibootmgr` it shows the list of efi variables
> (here i again added the ubuntu entry manually as i remember
> it):
> 
> BootCurrent: 0001
> Timeout: 1 seconds
> BootOrder: 0001,0002,0003,0004,0005,0006
> Boot0000  Windows Boot Manager	HD(1,GPT,...
> Boot0001* debian	HD(1,GPT,...
> Boot0002* ubuntu	HD(1,GPT,...
(...)
> as far as i understand the system uses BootOrder to determin
> what to boot.

Yes, in theory.

> it starts with 0001 which is debian, not
> ubuntu. so i wonder why the leftover ubuntu grub was booted as
> you say (which i believe, i am not an efi expert).

Unfortunately some UEFI firmware do not use BootOrder properly. When 
that happens the UEFI firmware may use another boot entry than the first 
one in BootOrder, or the removable media path.

>>> i dont know if it was just my mistake not to delete that dir when wiping
>>> ubuntu from the system  or the debian installer should notice that or
>> Notice what ?
> 
> that the system wont be able to boot into debian.

How would the installer know that the UEFI firmware is flawed ?

> maybe it could change BootOrder to point to the debian entry
> only?

It won't help if the firmware ignores BootOrder.
A usual workaround is to force GRUB installation into the "removable 
media path", but the option is offered only in expert install.
A patch to do it by default when the removable media path does not exist 
has been submitted, but it would not help in your case.