How to backup before a release upgrade from Ubuntu 18.04.5 LTS server?

[Colin Law]

On Sun, 12 Sept 2021 at 07:41, Bo Berglund <bo.berglund at gmail.com> wrote:
>
> My Ubuntu server, which is hosting subversion and a few websites, needs to be
> upgraded to 20.04.3 LTS from 18.04.5 LTS18.04.5 LTS.
> I have found a command line tutorial on how to do this here:
> https://www.cyberciti.biz/faq/upgrade-ubuntu-18-04-to-20-04-lts-using-command-line/
>
> It looks OK except for this:
> Step 1 (important) is to make a backup, but it says NOTHING about how to do
> that..
>
> I have tried to figure out how but failed, most search hits talk about setting
> up regular backup systems for the *data*, and they assume there is a desktop
> too. But this is a headless server accessed via SSH using PuTTY on Windows.

I  use clonezilla for full disc or partition backups.  As said by
others you will have to shutdown the server and boot from, for
example, a USB stick or if you have dual boots then boot from a
different partition to backup the Ubuntu partition.  Its big advantage
over dd or similar is that it only backs up used sections of the
partition which can be a huge space saving.  Also it can backup over
the network (using ssh) so you can make a backup image on a disc on a
different machine.

Colin