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On other operating systems, there are ways to see what process or event woke them from suspend. I leave my laptop often for multiple days in suspend, sometimes to find that it has woken itself up and is heating whatever surface it is resting on :)

Is there a way to find out what woke it up so that I can prevent that thing from happening again? On Ubuntu 12.04 (elementary Luna).

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marked as duplicate by slm, derobert, jasonwryan, Caleb, Braiam Jun 13 at 23:24

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The only thing I'm aware of that's commonly used to force a wake (besides, I guess, the hardware interrupts) is the rtcwake command. The source for that uses ioctl() calls on the real time clock device (by default, /dev/rtc0) meaning it must have privileges (so it cannot be anything you start on your desktop as a normal user).

I would be very surprised to learn that there is a privileged service on Ubuntu set up to do anything like that (why?). However, I do notice that occasionally a sleeping system has woken up for no apparent reason while left alone. I do not have a cat, so I assume this is something having vibrated the mouse, or maybe some weird voltage fluctuation, or some other random cause.

If this happens regularly, it may indicate a bug in the ACPI driver.

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Same here, it's only occasionally. I don't have a cat or a mouse attached, so it must be something weird. –  Naftuli Tzvi Kay Jun 13 at 19:46
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