My HP Probook 6470b runs Ubuntu 14.04.3 with default open intel graphic driver and proprietary bcmwl-kernel-source for BCM43228 wifi. It froze after I had turned wifi off and would not react on a pressed key so I coult not reach terminal with ctrl-shft-F1. Chrome was open.
How can I check what went wrong after I did hard reboot? What logs and commands should I check to find out a clue what has failed? Could dmesg survive reboot?
After a hard reboot it runs fine again. I know the time of a failure so I could perhaps find some errors in kernel logs?