Re: grub-install into hybrid MBR on GPT disk on legacy BIOS

[John Z. Bohach]

On 01/07/2018 03:47 PM, Pascal Hambourg wrote:
> Le 07/01/2018 à 21:52, jzb a écrit :
>> I have the EE partition first, and there's the EF02 for grub to install into.
> 
> Note that code EF (EFI) in DOS/MBR does not match code EF02 (BIOS boot) in 
> GPT.
> 
>> (grub-install -v --target=i386-pc /dev/sda
>>   /dev/sda1 is mounted as /boot [ext2 filesystem])
>>                                  ^^^^^^^^^^^^^^^ <- is this okay for 
>> hybrid???
> 
> No it's not ok, either for hybrid or protective MBR.
> It seems that you set the "BIOS boot" type on partition 1 but it actually
> contains an ext2 filesystem mounted as /boot. If you are using it as /boot,
> not as a BIOS boot partition, you should not set the BIOS boot type, or
> grub-install may overwrite it. A real BIOS boot partition has no filesystem
> and is not mounted nor used in any way by Linux. It must be reserved to GRUB.

And there it is :-).  That was it.  After my grub-install, I did a
grub-mkconfig, which then proceeded to update the very filesystem where grub
was embedded, thus destroying the embbedding, though the filesystem itself was
still somehow left intact.  All the hints I found just simply didn't make it
clear that the BIOS boot partition _must_ be a reserved partition and
otherwise left alone.  Problem solved.

Thanks,
John