It's getting cold and its a time to turn on my heater/miner again ;-)
I saw that this machine is still running Ubuntu 14.04. I think it would be time to upgrade/reinstall the entire machine at that point.
What do I need to backup? Which files/directories?
After that I will wipe out the hard disk and reinstall Ubuntu 16.04.3 server. Then install Monero again and then restore the files you suggested before I restart to mine.
Besides the backup, do I need to take care of anything else?