A bit of background in hopes that I can have the rest of this make any sense to other folks here:
I actually provide the support for a bunch of former windows users after setting them up with U/M.
They are very content with their PCs & generally speaking I am able to find whatever info I need if/when any problem may arise (seldom !!) - thus I post here ONLY if I am totally lost for finding workable answers.
So...
Lately I've completed a bunch of upgrades from 18.04.x to 20.04.2 for other folks' PCs.
Most went along just fine despite being quite time consuming & with good results.
I did run into a couple of instances which got very sticky as well, so I used alternate methods - the worst of which was actually wiping & totally starting over with a fresh installation of 20.04.2.
Tonight however was absolutely THE WORST experience of them all, sadly.
Given that today was a holiday here, I cleared all my earlier work & finally did this upgrade for my own desktop...and it failed to fully boot up afterwards.
It only got as far as the desktop wallpaper with a mouse arrow that alternated with the spinny cursor & there it stayed no matter for how long - and was otherwise totally unresponsive.
Fortunately - since I was aware that it could go fubar like those couple of others did, I had used an identically sized HDD beforehand & totally cloned my daily driver PC's entire OS & data - then tested it on my spare box to be 100% sure it was as it should be - which it was.
So, when my own PC's upgrade went totally fubar, I just deleted & re-copied in /boot & / and here I am, right back where I began before I'd wasted far too many hours on this absurdity of an attempted upgrade.
Yes - I have many apps & have made this PC's OS very much my own;
Up 'till this botch it was working perfectly each & every single day, so:
It can stay as it is so that I don't get stuck like that again - and...
Later I'll re-create my preferred configuration on my spare box as time allows with 20.04.2 then freshly installed as its base.
All that having been said - after doing lots of these upgrades - and after looking for any simpler ways to go about it - I have some questions which I have not found helpful answers for, please:
1 - Knowing I might need it, I got the 20.04.2 ISO & had it near to hand - so just for yuks (as the answer was already in mind...) I did a live boot of it with another 18.04 setup connected to see what it might offer.
No direct route from that session to any upgrading was obvious - just as I expected.
I had read before that it could be done by doing an over-install whilst preserving /home & then reinstalling needed apps - so I tried that - and frankly saw zero advantages after the efforts needed in doing it that way !!
Query:
Short of making some local server with the repos, etc. in it - it there any method to do multiple upgrades SIMPLY & EASILY via some local media so as to avoid doing the downloading process for EVERY upgrade over & over & over ??
Query 2:
Is there some sort of upgrade data or media that can be gotten that is intended JUST for upgrading an existing system ??
Query 3:
Short of doing all the careful preparation & steps that I did for this roll-back, is there some better method for recovering from a botched upgrade that refuses to boot fully and is totally unresponsive ??
I did consider entering recovery mode and playing around with that & DPKG, etc. - but since I actually needed to get back to work tonight I had already wasted FAR more time on the botch than it deserved, so I did not try any of that sort of stuff.
My closing comment:
This result is the sort of thing that has folks pointing to Linux in general as being too fiddly and/or techie.
Even with my years of being a very happy & satisfied Linux user this seriously messed with me 'cuz it SHOULD have gone flawlessly - but did not even come close to that after I wasted too much of my day patiently trying to get through the process.
Thanks for any helpful pointers in reply !!