Upgrading to Ubuntu 20, *how* to back up?

[Peter Flynn]

On 25/04/2020 21:22, Colin Law wrote:
[...]
> The recommendation is to backup the whole system, at least that is how
> I read it.  Whether it is a sensible recommendation I am not sure.

In general, yes, it would always be a good idea to have a backup of the 
entire system, but in practice — for the normal end-user — this is 
overkill.

Firstly because the "normal end-user" probably doesn't store anything in 
the system directories, only in /home/<name>; and secondly because if 
you are upgrading to a higher version, the contents of the system 
directories will not be relevant as it will all be recreated anew.

The only time you might need the system backup is when you want to 
restore to the earlier version of the operating system that you backed 
up, but the easiest way to do that is just install it afresh.

The big IFF is for people who are *not* "normal end-users". If you have 
used admin privs (sudo) to modify the system installation, perhaps 
editing system-wide config files, then you are on your way to becoming a 
systems administrator, and you will (of course) have kept a notebook 
detailing all the changes you have made, so that they can be tested and 
reapplied if necessary on a new system :-)

So the test is: have you made changes outside /home/<name> that you want 
to carry forward to a new system? Do you know what those changes are, 
and when and where they were made?

If you want to do a system-wide backup it's very easy using a tool like 
rsync to copy everything except the mount-point where your external USB 
drive is attached. Copying it back in the case of wanting to revert is 
much harder, because you risk overwriting the executing system (which 
you want to do, of course, but not while it's executing!). This is where 
a specifically-designed backup tool is needed (like timeshift).

Peter