I recently tried to upgrade a machine from Ubuntu 14 to 18 via
dist-upgrade. The update appeared to proceed without problems. However, after rebooting and choosing 'ubuntu' from grub the splash screen loads with the dots underneath but gets stuck (no progress or keyboard / mouse input) after each dot has flashed once.
I have tried pressing ESC to display the text interface while booting. This works sometimes if I press it quick enough but the text is often a little jumbled, although sometimes not. I have also tried turning off the splash from grub by pressing e and editing the options. This however just gave a blank screen. I also tried selecting the 14.04 option which is still in grub. This boots fine. Re-running
dist-upgrade from 14.04 didn't work. I also tried boot-repair from 14.04 to see it if would help but it just renamed and reordered the grub entries to make the 14.04 option 'Ubuntu' and the Ubuntu 18 option 'Ubuntu 18.04'.
When the text interface does work it appears to get stuck either at the part where it is waiting for entropy or just after these lines:
[ OK ] Started Network Manager Script Dispatcher Service. NetworkManager-dispatcher.service [ OK ] Started GNOME Display Manager. gdm.service _
Any ideas how to sort out this mess and get the 18.04 upgrade to boot?