16.04 and 20.04 side by side on one harddisk

[Bret Busby]

On 19/3/21 2:00 am, Lentes, Bernd wrote:
> Hi,
> 
> we have an Ubuntu 16.04 installed on a normal pc. It has installed a lot of applications, especially Bioinformatic tools which have been complicated to install.
> We are thinking of upgrading to 20.04, but want to keep the old installation as an emergency solution.
> I'm thinking of installing 20.04 beside 16.04 so that we can try to get all applications running on 20.04, but still having 16.04.
> I never did that before, that's why i asked. Is that possible ?
> I assume Grub is intelligent enough to recognize the old system during the installation of 20.04 and insert it in the boot menu.
> Yes ?
> Beside the two systems we have large partitions (several TB) with data.
> 
> Another idea is to use virtualization, KVM. Install KVM on 16.04 and install 20.04 in a VM.
> So we have both systems running simultaneously.
> We could change the FS of the data partitions to OCFS2, so concurrent access should be possible.
> I found an article using OCFS2 without pacemaker, it seems to be easy.
> Can i access partitions directly with a VM under KVM ?
> 
> 
> Bernd
> 


You can have multiple versions installed on the same computer, using 
GRUB or some other bootloader, to select which to run.

On one of my systems, I have 20.10 and 16.04 installed. I previously had 
three or four different version numbers installed on that computer, and, 
using GRUB, was able to select which version to load and run.

I do not use virtual machines.

I store as much data as possible, in dedicated data partitions.

You can mount and thence, access, data partitions, using later versions.

I can access my 16.04 /home partition, from my 20.10 installation, 
without any problems.

I am not a Linux expert - I am a Linux (UbuntuMATE) user of limited 
skills and abilities, but, have been using Linux for about twenty five 
to thirty years.

Depending on your "normal pc" - whether it has UEFI, or only legacy 
BIOS, 20.04 can, from memory, install directly using UEFI - without 
having to switch to Legacy BIOS, and, similarly, for loading and running 
it at bootup.

I am not sure (someone more knowledgeable than me, can clarify this), 
but I think that 20.04 was the first version that could be installed, 
and, loaded and run, directly through UEFI.

-- 
Bret Busby
UbuntuMATE User and Campaigner
Armadale
West Australia
(UTC+0800)
..............