On June 29, 2020 12:37:45 AM GMT+02:00, Hendrik Boom <hendrik@???> wrote:
> Where is it configured which drives get updated when I update the kernel,
> as part of a regular upgrade using aptitude.
>
> Presumably it has to install the new kernel, build an initrd, find out
> what other bootable systems are available, write a new grub
> configuration, and possibly update the MBR and stage1 of Grub ...
>
> Now somewhere there must be a configuration which hard drives' MBRs and
> stage1's have to be written


AFAIKT AFK, grub2's configuration resides under /boot/grub/ (written by update-grub).

On the other hand, grub-install writes the bootloader itsself to the MBR resp. some partition - including the information, where the aforementioned configuration can be found.

Thus, update-grub (as called by apt for e.g. a kernel upgrade) does not need to know, where the bootloader binary is installed. Only when this binary is installed the first time or needs to be updated, grub-install prompts for the target location.

You can have the bootloader installed on every disk's MBR and in every partition simultaneously, as the BIOS resp. the 'boot' flag define, which one gets called.

libre Grüße,
Florian

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