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As of several days ago, my MacBook refuses to go to sleep either automatically or manually. I have taken the following troubleshooting measures to no effect:

  • Reset PRAM
  • Rest SMC
  • Boot in SafeMode
  • Verified that the lid sensor was working (my MacBooks's status light responds when it's closed)

Anyone have any ideas would could be causing my MacBook's incompetence? I'm on 10.7.2 btw.

UPDATE: I found the solution to the problem: I had unnecessary sharing services enabled despite not using them for weeks. Turning these off fixed the problem :)

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How do you know it's not going to sleep? – Michiel Oct 28 '11 at 8:50
Fan and HDD still spinning, and the status light is constant on, not flashing – AMomchilov Oct 28 '11 at 18:16
You should post your update as an answer and accept that. – Josh Oct 30 '11 at 16:58

I found my answer here.

To sum up:

  • Open a terminal
  • Run "pmset -g assertions"
  • Check the output if there is any process preventing the system from sleeping.

In my and apparently many people's cases, it was actually an unused printer driver that seems to be in "in use" state. I deleted that printer driver (not all of them!) and my system now goes to sleep peacefully after closing the lid (even on power).

Lion seems to keep the system awake if the power is connected and there are any services or devices shared to others.

Btw, I am still getting that sound assertion failure when the system goes to sleep.

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up vote 2 down vote accepted

Unnecessary sharing services might interrupt the sleep process. Turning these off fixed the problem :)

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You've tried the few things I'd recommend before going down this route, but trashing the sleepimage and changing hibernate settings can help. Note I take no responsibility if your Mac eats your dog.

Aside from that I'd suggest checking the syslogs when you shut the lid to see if the hibernate signal is actually being fired and what OS X is doing, and see if there's any errant processes that could keep waking it.

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No sleep image to be found=/ – AMomchilov Oct 28 '11 at 18:23
"MacBook:/ Alexander$ sudo rm /var/vm/sleepimage rm: /var/vm/sleepimage: No such file or directory" – AMomchilov Oct 28 '11 at 18:23
Well that's an interesting pickle. What int value do you get returned from the pmset command? – Nicholas Smith Oct 30 '11 at 21:30

Do you have a Magic mouse and do you have bluetooth turned on? Try turning bluetooth off and/or the auto-discovery piece of sensing mouse movement from a magic mouse or some other bluetooth device.

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I found an extensive checklist for troubleshooting this issue in the Apple forums: MacBook Pro does not sleep when lid closed

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