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We have a laptop cart with a bunch of Dell Latitude 5490's running Ubuntu Desktop 18.04. I'd like these to reboot nightly at 4 am. The cron job is simple enough, but it never runs because the laptops are hibernating with their lids closed.

I looked at rtcwake but documentation is confusing -- are RTC, BIOS clock, and hardware clock all different things? Sometimes these terms seem to be used interchangeably and sometimes not. My laptops sync their clocks to our NTP server (UTC - 4) but the BIOS clock still show UTC + 0.

Setting a startup time in the BIOS didn't work either, and I tried it both with local time and UTC.

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  • WOL seems to be supported, but then I would need to configure a server to send a wake-up packet, right? I would prefer a system that didn't rely on a centralized push.
    – FloobyNooby
    Jul 27, 2018 at 15:59
  • We have an Acer laptop that has WOL baked in - I don't think there is even a way to turn it off!
    – Organic Marble
    Jul 27, 2018 at 16:40

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How about rtcwake? It's a kernel module that can monitor your system from the moment it goes to sleep to see if it needs to wake up for a specific job.

Documentation https://linux.die.net/man/8/rtcwake

Mini-howto http://www.osnews.com/story/24111/Wake_Your_Linux_Up_From_Sleep_for_a_Cron_Job

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  • I'm trying rtcwake again ... will find out Monday morning if it worked!
    – FloobyNooby
    Jul 27, 2018 at 19:40
  • Didn't work. The laptop slept through the whole thing.
    – FloobyNooby
    Jul 30, 2018 at 13:48

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