From 15.04 to 15.10 (command line upgrade)

[cogset]

I shall apologize in advance for this well known question, however if I may ask: now that the time has come to move from 15.04 to 15.10 (BTW, that being the main reason why I've always used only LTS releases, i.e. I don't like frequent system upgrades... but the official Ubuntu-Mate release available was 15.04, so I went with it) how inappropriate would be to upgrade in the so called "debian way", in other words ensure that the system is currently up to date, edit the sources.list file to point to the 15.10 release, then go ahead with apt-get update followed by apt-get dist-upgrade?

You may ask why go the trouble, well I've been managing package(s) installing and upgrades from command line for a while now, so bringing up the update manager and let it do all the work looks like taking a step back to me.
I understand it does some behind-the scenes work to set things properly for a full system update, but I'd like to get more in control: of course I have a recent full-system backup already, and I have a standard installation as far as I can see, meaning no ppas have been added, no alternative kernels, no custom built packages and no packages from backports or proposed updates have been installed that I know of (at least, I've never purposely installed a package from backports with the -t vivid-backports option) .

I have however all old kernels still left behind, I should have cleaned them but I think I can still do that before the update and just leave the latest one.

If I go that route, I would of course first simulate the upgrade to check that nothing important gets removed or that some unmet dependencies get in the way - therefore, I could always put the original sources back in place and launch the update manager. Any thoughts? Any reason why that could fail and/or break the system?

[QIII]

Hello!


apt-get dist-upgrade

will not take you to the next release. That command will upgrade your current release to its most recent and updated components -- but still leave you at 15.04.

The command
do-release-upgrade is what you are looking for (https://help.ubuntu.com/lts/serverguide/installing-upgrading.html).

As to whether or not that is appropriate, it is up to you. Make sure you do


sudo apt-get update && sudo apt-get dist-upgrade

and


sudo apt-get autoremove

first to be sure everything, including the kernel & headers, is up to date.

Could it fail and break your system? Yes. Is that likely? Hard to say.

If you have complete backups, you mitigate your risk.

Personally, I always do a fresh installation to be sure that all the cobwebs are swept out of the corners.

[cogset]

I believe you may have missed this line which I have now highlighted in my post:


edit the sources.list file to point to the 15.10 release, then go ahead with apt-get update followed by apt-get dist-upgrade

of course I didn't intend to move from 15.04 to 15.10 just by means of dist-upgrade alone.

Again, I have a full back up and I'm going to first simulate the upgrade process with apt-get -s upgrade to see what is going to happen, I'm just curious as to why this method is generally not advised: I get that the update manager makes things much easier, but what is that possibly makes Ubuntu more prone to breakage (IF that is the case, I'm not claiming it actually is) when relying on traditional command line apt tools for upgrading?

As for completely reinstalling...well, I think I get the general idea, but after running this OS for not even 6 full months, that seem definitely overkill to me: I've been using some LTS releases for more than 5 years (yes, even after support ended) without issues, besides I'm annoyed enough that I've had to pick a non-LTS release in this case, reinstalling would be just too much for me.

On regard to that, I always disinstall some packages that I don't need, disable services I don't want, modify some config files in /home and /etc, add a couple of commands to rc.local and maybe .xsessionrc : in short, I'd definitely want to keep all these modifications and not overwrite anything or install again packages that I've already removed.

[cogset]

So, it's done: I've purged older kernels/headers (as should I have done way before), made a backup, then simulated the update with apt-get -s upgrade and apt-get -s dist-upgrade first, after checking that there were no warnings or broken packages I've finally removed the -s option and upgraded from 15.04 to 15.10.

Other than losing a custom terminal image background and the lightdm greeter background, everything else looks OK.

Again, I'm curious about the technical reasons for which a command line upgrade is generally discouraged for desktops: is that just for the sake of an easy upgrade option using the GUI (which I can understand) or are there more technical reasons behind this?

What should I eventually check to make sure that I haven't a broken system?