Today my Ubuntu 12.04 server started crashing once an hour. It's actually right at minute :32, every hour. It seems to be an actual kernel crash, i.e. there's nothing in /var/log/syslog, it just stops. I even wrote a script that printed out the time every second to try to nail down the exact time, and watched as the next crash was coming, and the best I can tell is it's about 32 minutes and 13 seconds after the hour.
But I have no CRON jobs running at that time, nothing. The ones I do have are the same Perl scripts I've had running for years that don't do anything special. I haven't changed anything on the server in probably weeks, and definitely nothing important. I've gone through every source of scheduled tasks I can find. Nothing special happens at that time except the server crashes without leaving any trace of why.
When it does crash, I have no choice but to reboot it through the hosting company's website, which has been my solution so far, but now it's 4am and I have to get some sleep sometime. But if I do, my site will go down within an hour. Any help would be appreciated, either a) how to find this task that is running and causing the crash, if that's what it is, or b) how to trace what's happening when it doesn't appear in syslog or dmesg.
SOLVED. I contacted my host. Apparently they installed new server monitoring software that flagged mine as using too much disk I/O. Instead of telling me, this software of theirs simply killed my server. It runs every hour at :32 minutes.