I was upgrading Ubuntu on my server (but Ubuntu is in desktop version) when mouse and keyboard stopped working :( So the screen went black (screensaver), and now I can't do anything. I don't know what stage of upgrade it stopped working, probably now it waits for me to answer some question.
Keyboard and mouse were connected by KVM, connecting them directly doesn't help. Both are on USB.
What I can do, is connecting to the machine by ssh. Can I somehow see and answer questions of update system and somehow finalize process of upgrade?