16.04 to 18.04

[Colin Law]

On Sun, 18 Nov 2018 at 15:27, Jack McGee <jack at greendesk.net> wrote:
>
> I am trying to upgrade this machine.  No luck.  Software Center does the
> same thing. Is it a repository issue?
> ...
> #Zesty
> deb http://us.archive.ubuntu.com/ubuntu zesty main
> deb-src http://us.archive.ubuntu.com/ubuntu zesty main

You have specified some zesty repositories for a Xenial system.  You
may be in trouble trying to upgrade.  First check you actually are on
xenial by doing
lsb_release -a
and make sure it says 16.04

If it says 17.04 then I don't know what the best thing to do is as
17.04 is out of support so it may not be possible to upgrade from
there.  If it says 16.04 then, in your place, I would comment out
those two lines and run
sudo apt-get update && sudo apt-get dist-upgrade
and see if you are able to bring it up to the latest 16.04, and if ok
then try the release upgrade again.  Make sure you have everything
backed up first though in case of disasters.

Possibly others may be able to suggest a better course of action, but
once you get into a mixed version system then things can get sticky.

Colin