Re: A Question About Two Bullseye OS on different Dives.

[Dynosaw]

I did something similar a couple of years ago when I installed Arch on a 
PC with Debian-Buster and a  BIOS Legacy option.
I can't say whether this procedure will work with UEFI, since I haven't 
tried that. You proceed at your own risk.


1.  Power the computer OFF and disconnect all external cables.
2.  Remove the cover and disconnect all hard drives from the motherboard 
(i.e unplug the SATA cables)

3.  Connect the target hard drive to the first SATA port on the motherboard.
4.  Reconnect only the essential external cables (power, keyboard, 
mouse, monitor).

 You can leave the cover off for the installation bit.
5.  Insert ISO-stick or ISO-DVD, power-ON, and install in the usual way 
on what is now the only hard disk
6.  When the installation is complete, reboot the PC to check the 
installation works.

7.  Power the PC OFF, remove all external cables as a safety precaution.
8.  Reconnect all hard disks in the preferred order, and put the cover 
back on the box.

9.  Connect all external cables and start the PC.
10.  Run  update-grub (as sudo/root). If all goes well Grub should run 
os-prober and find both operating systems.

It worked for me, but your mileage may differ

Good luck
Dynosaw
--

Re: A Question About Two Bullseye OS on different Dives.

[Andrew M.A. Cater]

On Sun, Feb 06, 2022 at 05:10:16PM -0500, Stephen P. Molnar wrote:
> My main Debian platform has four drives:
> 
> /dev/sda500GB Buster
> /dev./sdb   1  TB
> /dev/sdc500 GB
> /dev/sdd1TB  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