Copied system partitions to USB disk, how to proceed to make a clone?

[Bo Berglund]

On Tue, 19 Oct 2021 15:16:41 +0200, Bo Berglund <bo.berglund at gmail.com> wrote:

>>Or, see if 18.04 will install -- then the EFI boot files will match versions.
>>
>
>I will install 20.04 first and see if I can switch the Ubuntu partition from
>20.04 to 18.04 after I have verified that it all works so far.
>
>QUESTION:
>---------
>I have never used dual-boot systems before and now I wonder if there is some
>kind of menu popping up on start which needs to be interacted with in order to
>boot the correct system?
>
>If so, how can I issue a sudo reboot from an SSH session to Ubuntu so it will
>reboot to Ubuntu and not Windows?
>I will not be able to see the boot menu if such is popping up since at that time
>I have lost connection by SSH.

Seems like the top item in the boot menu will start after some 10 seconds
timeout.  I don't know how the top line is set though...

>This is by far the most advanced Linux operations I have done, my only exposure
>before has been to install Ubuntu Server 18.04 on two PC:s and then install
>openvpn etc on them.
>And of course all of the Raspberries I have cluttering my desk...
>But these are all one-off installs on SDcard.

I have now installed Ubuntu 20.04 LTS and let it update itself.
I selected to install the "minimal" version concerning apps etc.

It actually took all of the remaining space (415 GB) for itself, using only 14
GB and leaving nothing at all for my home dir...

So now I have to somehow shrink the partition back to something sensible so I
can transfer the home partition from my backup disk.

I guess that means I have to again try and boot off the installation USB and use
GParted from there?

QUESTION
--------
Can I have another Ubuntu (my old server) as a boot menu item on this PC?
I.e. can I copy in the system partition and then modify the boot loader setting
such that it can select between Ubuntu 20.04 and Ubuntu 18.04?
How can that be done?


-- 
Bo Berglund
Developer in Sweden