After an upgrade and reboot, my Pi (running Raspbian) shows activity (the lights come on) but the router to which it is wired no longer recognises it. I have no suitable standalone monitor and have to diagnose it by reading the memory card in my laptop.
The latest logs in /var/log are from the last shutdown before the problem arose and show nothing wrong.
Is there anything else which might give some clue as to why the network no longer comes up?
And if I have to reformat the card and reinstall everything, is it possible to find the cron data to copy over?