Re: A Question About Two Bullseye OS on different Dives.
On Sun, Feb 06, 2022 at 05:10:16PM -0500, Stephen P. Molnar wrote:
> My main Debian platform has four drives:
>
> /dev/sda 500GB Buster
> /dev./sdb 1 TB
> /dev/sdc 500 GB
> /dev/sdd 1TB Bullseye
>
> The boot order is /dev/sr0 then /dev/ssd, which i want to keep. Now grub
> comes up with /dev/sdd as the default and /dev/sda as the second choice.
> What I want to do is install a second Bullseye on /dev/sda without changing
> the grub boot order. How do I go about accomplishing this?
>
> I have googled the question and not found an answer that I understand.
>
> Thanks in advance.
>
> --
> Stephen P. Molnar, Ph.D.
> www.molecular-modeling.net
> 614.312.7528 (c)
> Skype: smolnar1
>
Hi Stephen,
Let's see if I can parse this:
First assumptions:
=================
I'm assuming that you're booting BIOS/MBR/legacy and not UEFI.
If this is incorrect, tell me.
You have a disk (/dev/sdd) that you want to boot Debian and you want it
to be seen as the primary disk.
It has GRUB on it.
You can set the order of drives in the BIOS so that they will boot in a
particular order.
1. If you were to set this physical disk as the second booting device (after
sr0) and disconnect all the other drives, it would boot Debian.
So far, so standard for a machine with one drive.
2. You now add a second drive - your drive (/dev/sda) and install Buster
on it. If you were to install GRUB to it and disconnect the other drive, it
would be bootable as if it were a single drive.
If, instead, you install to the first bootable disk, you'll add the GRUB
stanza on /dev/sdd (I think).
If you shrink the Buster install on /dev/sda and add a new Bullseye install
into the freed space, you'll need to update whichever GRUB boots that disk
to add a second stanza.
If you want to chainload GRUB from /dev/sdd to the GRUB on /dev/sda you can
do. Otherwise, make sure that there are stanzas for all the GRUB boot
on the first bootable hard disk - which for you, given the boot order,
would be /dev/sdd.
To be honest, this is now all far easier from UEFI in my humbe opinion but
I could be both a) biassed and b) very, very wrong - people's needs vary.
All the very best, as ever,
Andy Cater
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