Aug 09, 2013

The case of the late night system boots

A few weeks back, at around 3:00AM I was woken up by the sounds of a computer booting. It turned out to be an old Ubuntu desktop in the study. Since it was storming at the time, I figured it due to a power outage so I shut down the machine and went back to bed.

A couple nights later the same thing happened. This time I made sure the BIOS on the machine was set to restore the machine to its previous state after an outage instead of turning it on. It turned out it was already set to restore the previous state. Odd, but it was 3:00AM so back to bed I went.

The third time it woke me up was soon during the time Thinkhost/Dreamhost dropkicked the old site in the gonads, and I start freaking out a little - I wasn't getting email, my corny vanity site had disappeared and I had a machine turning itself on in the middle of the night. It was coming out of hibernation when it started, so when I noticed it, I was already logged into the console and my 3:00AM self didn't notice any weird activity on the machine. I poked around on the BIOS again to make sure the Wake-on-LAN options were not set and powered down the computer. Still, I started pulling Ethernet cables out before going to bed until I had a chance to really figure out what was going on.

Then over the weekend I had started the machine up and then started some Laundry [*]. When I eventually got back to study, the machine it was still one. I'd been gone long enough that it should have gone into hibernation by then. I did a 'sudo /usr/sbin/pm-hibernate' manually and it went through its normal hibernate routine, but after it powered down, it immediately booted back up again !

Then it all made sense - the machine had been trying to hibernate and rebooting, then waiting some number of minutes with no keyboard activity and repeating the cycle. If I was sleeping lightly enough at the time , the beeps during the restart would wake me up, otherwise I was sleeping through all the restarts. Eventually someone in the house would notice the machine was on and shut it down gracefully. I have no clue how long hibernate had been failing like this. Weeks at least.

But onto the solution. I didn't find much on the Internet about the problem (hence this post), but the combination of the basic-pm-debugging.txt and the pm-hibernate man page led me to try adding an '/etc/pm/config.d/hibernate file with the contents:

HIBERNATE_MODE=shutdown

With that in place, pm-hibernate went back to working like it used to, and I haven't been woken up by late night restarts since.

[*]For purposes of this blog, 'Laundry' is any non-computer indoor activity and 'Going for a Walk' is any non-computer outdoor activity.