Re: [gentoo-user] Duel boot - How to verify boot loader updates?

[Michael]

On Friday, 9 December 2022 17:17:24 GMT Mark Knecht wrote:
> On Fri, Dec 9, 2022 at 4:07 AM Arve Barsnes <arve.barsnes@×××××.com> wrote:
> > On Fri, 9 Dec 2022 at 11:55, Michael <confabulate@××××××××.com> wrote:
> > > To check the GRUB version of the second OS without booting into it, you
>
> can
>
> > > grep for grub in its /var/log/emerge.log
> >
> > Or see what version is named in the /usr/share/doc/grub-2.?? folder name.
> >
> > On the other hand, if the question is *really* about knowing if
> > grub-install has been run on one of the machines, I don't know if
> > there is a way. Probably look at change dates on the files in
> > /boot/grub/?
> >
> > Regards,
> > Arve
>
> Thanks to both of you for your responses. I appreciate them, although I
> don't think they get as far down in the weeds as I was wondering about.
>
> My understanding of the boot loader - and maybe I'm using the wrong
> terminology so if I am someone please correct me - is that at the start
> of boot BIOS tells the processor to read some part of the disk and it is
> the code read there that gets the whole process kicked off and
> out of BIOS's control.
>
> I'm wondering about that first bit of code being written by installation
> #2's update into the initial section of installation #1's disk.
>
> Rethink the picture a bit and make installation #1 Windows and
> installation #2 Linux. Assume that after updating each install, and
> further assume both installs made some very minor change to their
> own first bits of code on the disk, and assume everything still
> boots correctly, BUT assume that one of the updates actually
> wrote into the other install's initial boot code and replaced it with
> their own because it was confused about which disk it was
> supposed to put this on. How would I be able to determine that
> this happened?
>
> It's not totally a thought experiment. One machine I have which
> is dual boot recently complained that the original disk grub was
> installed on had changed when in fact there hadn't been any
> hardware changes and I had to carefully figure out how to
> answer a couple of questions. After the fact I started to wonder
> about this edge case.
>
> I think it comes down to reading what's on the disk with a
> hex editor possibly but I know nothing about what to expect
> there.
>
> Thanks,
> Mark

Before I venture a potentially wrong answer, could you please clarify if we 
are talking about a UEFI MoBo, or a legacy BIOS MoBo.