How to find out what turned off the computer?

Question

Yesterday, after getting back home I found out my computer is turned off. Since it appeared it was cold shutdown (a lot of disk repairs were shown during boot up) I am wondering what was the cause. For this particular shutdown I probably won't figure it out, but how to set up system (openSUSE 11.4) to log the possible causes in such way, that if nothing is logged it would have to be power cut off.

For now, I can think of several causes of cold shutdown:

• pressing turn off button (in my case not possible)
• overheating (possible, because one reason could be fan malfunction, and this can happen)
• power outage (possible)

I cannot think of anything else. I rule out cracking into the system, because in such case shutdown would be clean.

So, the question is -- how to set up your system, to be prepared for later finding out the cause of cold shutdown?

Answer 1

One thing I would do is have a look at /var/log/syslog. It's where Linux kernel and a bunch of other programs (dhclient, NetworkManager, acpid, dbus, ...) log some of their messages. It's extra nice because it will include which log line belongs to which program.