On 29-06-2020 17:13, Hendrik Boom wrote:

> On Mon, Jun 29, 2020 at 12:44:05PM +0000, dal wrote:
>>> From: Dng [mailto:dng-bounces@lists.dyne.org] On Behalf Of Hendrik Boom
>>> Sent: den 29 juni 2020 14:18
>>> What I want to know is:
>>>    What determines which disks' MBRs get written to during a 
>>>    normal kernel upgrade initiated by aptitude.
>> A normal kernel upgrade does not, nor needs to  rewrite MBRs.
> Grub stage 1 resides within 446 bytes of the MBR.
> Grub stage 1.5 resides in the spae between the MBR and the first partition.
> Grub stage 2 resides in the /boot within a partition.

>
> It's entirely plausible that some of stage 1 and stage 1.5 may need changes.
>
> In any case, the last upgrade I did tried to write in the space between
> the MBR and the first partition of on of my hard drives.
>
> I'd like it to stop trying that, letting it write to my other drives and
> never boot from this one again, which I plan to remove when I find my
> screwdriver.
>
> -- hendrik
>
>> /D
>>
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According to grub documentation you can make grub-mkconfig skip a drive
with one of these options in /etc/default/grub

'GRUB_DISABLE_OS_PROBER'
     Normally, 'grub-mkconfig' will try to use the external 'os-prober'
     program, if installed, to discover other operating systems
     installed on the same system and generate appropriate menu entries
     for them.  Set this option to 'true' to disable this.

'GRUB_OS_PROBER_SKIP_LIST'
     List of space-separated FS UUIDs of filesystems to be ignored from
     os-prober output.  For efi chainloaders it's <UUID>@<EFI FILE>