How do I resume a release upgrade?

Solution 1:

It appears that sudo screen -D -r will reconnect to a disconnected install in a 12.04 to 16.04 upgrade. This means no killing of packages or anything like that. This assumes that you didn't actively stop the upgrade, just lost access to the session.

Solution 2:

Try these steps, from the command line:

Fix broken dependencies:

$ sudo apt-get install -f

If it still doesn't work, try this to fix/reconfigure the existing, unpacked-but-not-yet-configured packages:

$ sudo dpkg --configure -a

Then try the upgrade again.

If it fails again, you may want to delete all the already- downloaded packages (they should be stored in /var/cache/apt/archives), do

$ sudo apt-get clean

That will clean up the packages but if you're still stuck in some weird state, I'm not sure what else to suggest.

$ sudo apt-get autoremove -y

That will remove any now obsolete packages.

Of course, before you do anything you should back up any important contents of your /home/dave directory (or whatever your $HOME directory is).

Solution 3:

My 16.04 to 18.04 upgrade had interrupted as I had stopped the process by mistake. I guess the process was towards the end (installing wifi packages). Nothing of above worked and kept giving "dpkg fronend is locked by another process". A system reboot followed by

$ sudo dpkg --configure -a

resumed the process and completed upgrade to 18.04 successfully.