Something strange just happened that hasn't ever before since I've been using Linux. I was viewing a page in Firefox and had just clicked "Send" in Thunderbird to send an email, when the system hung. The mouse stopped responding and the hard disk activity light showed constant activity. The mouse and buttons had no response, Ctrl-Alt-Backspace didn't kill X, and Ctrl-Alt-F1, F2, F3, etc. didn't do anything either. Closing the laptop lid did not suspend the system as it normally does. I waited a couple of minutes, but nothing changed and the hard disk continued to show activity. I ended up forcing shut down with the button and starting again. Nothing seems to be wrong, and the only thing I see in dmesg on startup is:
ide0(3,3):Removing [15607 60887 0x0 SD]..done
ide0(3,3):Removing [15607 33449 0x0 SD]..done
ide0(3,3):There were 2 uncompleted unlinks/truncates. Completed
First, forcing shutdown while the disk is active doesn't seem like a good idea, so is there anything I can do to confirm nothing was damaged (other than whatever that dmesg message shows). Second, what could cause this to happen? It was my understanding that you should always be able to get out of X or switch terminals, at least. What can I look into, and what should I do if it happens again? Thanks in advance.