My Lubuntu trusty isn't especially trusty when it comes to sleep. Where can I find a log of events that are keeping it awake?

maybe dmesg.

why not just switch it off?

You jest, sir...

Thought of dmesg, but it's festooned with other messages, so it's hard out there for a noob.

Is there not some place where xfce4 power mgr (or whatever watches these sleep disturbing events) keeps its own?

I assume the PC is running and you hear the hard drive spin up. Typically, there are one or more system cronjobs that run at night.

/var/log/syslog

let me take the opportunity to say something about this.
because i stumble upon this sort of reply quite often - the argumentation here seems to be:
that i, or others who have been using linux longer than the self-confessed noob, have some kind of magic ability that makes it easy for them to read log messages. well, let me tell you, it isn't. it is still very much a pain in the brain. maybe less so than 3 years ago (when I was the noob), but it still is.
and, like in so many social situations (nothing to do with computers!), i have the choice to
a) read the logs for you, thus creating more and more situations for myself where I have to do the dirty stuff (again)
- or -
b) tell you to go through it yourself and learn to actually read it, thus gathering experience and the ability to help yourself.

Wake from some choice would be in Bios and maybe other places. Find all possible choices and then diag them.

People seem to leave on wake from lan on. A lot of crooks look just for that.

It's not that the systems wakes up, it's just that it never goes to sleep in the first place. The sleep function must naturally be--while still awake--looking for certain events to keep or reset the inactivity timer to 0 secs. I'm trying to figure out what events are doing that long after I've walked away from the server.

Not worried about crooks in this case, but I can appreciate the comment on that score.

Update:

If I restart the xfce4-power-manager or simply change a setting and save, it will sleep pretty much on schedule. Then, after some experimenting, I figured out that if I wake the system without using any keystrokes (WOL or pwr-button, e.g.) it will never sleep again unless I enter a keystroke. Somehow it would appear that without a keystroke (or possibly mouse--didn't have one handy) the timer never starts again.

Thoughts?

Bueller...?