Which log will tell me why my computer shut down?-Collection of common programming errors

I was at school SSHing to my homebox. All of a sudden, my connection was closed. Attempting to reconnect failed. When I returned home, I discovered that my computer was off.

Nobody was at my house and I am sure that I did not have a power outage.

How can I figure out how or why my computer shut off? Is there some log in /var/log that could point me in the right direction? Should there be a core dump somewhere that I should find? If so, how do I use core dumps?

1. The relevant files in /var/log are messages, dmesg

   issue, command ‘last’ to see the exact reboot time. You will see a line starting with ‘reboot’ (or may be shutdown) for all reboot/crash.
   cat /var/log/messages from a terminal and check for messages at the time stamp of reboot or just before it. ‘dmesg’ can give the last boot time messages.

   Hope this helps.

2. It is unusual for a kernel error to shutdown the power, it would either hang with a kernel panic or reboot. It was most likely an hardware issue.

   If there was a kernel panic search for “kernel panic” on the logs dir:

   grep -r "kernel panic" /var/log