The past couple days, command-option-eject no longer puts my Mac Pro to sleep. I haven't done any software updates in that time. No process seems to be doing anything very interesting, or CPU-intensive.

What's stopping my Mac from being able to sleep? How can I figure out what it is?


Open Terminal application in your utility and type

syslog |grep -i "Wake reason"

You shortcuts keys must have changed (with or without your intervention)

Make sure you have no hot corners enabled to keep it awake (System preferences Desktop > hot corners)

  • I get a few lines that look like: kernel[0] <Debug>: Wake reason: EHC2. Google suggests that this is USB-related, and I remembered I've been using an old USB mouse recently because the batteries in my Bluetooth mouse died. Unplugged the USB mouse, and my Mac sleeps again! – Ken Aug 3 '13 at 15:48
  • You are welcome :) – Ruskes Aug 3 '13 at 15:53

Using the Terminal application on macOS Sierra 10.12 or later you can run the following:

log show --last 2d|grep "Wake reason"

This will provide a list of the various reasons your system is not sleeping. Unfortunately the list will likely contain a few things that are not immediately clear, but a quick search on those messages should lead you in the right direction.

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