How to Troubleshoot a Mac That Won’t Wake From Sleep

| MGG Answers


Larry writes: Occasionally, I will come home to my Mac Pro, which I had set to sleep, and find it powered up but with a black screen. No combination of keystrokes or mouse movements can wake it and my only recourse is to perform a forced shutdown, endangering any data I had opened when the Mac originally went to sleep.

What could be causing this and how can I stop it?


There are several troubleshooting steps we can take in situations such as this one. First, let’s look in Console.

The next time you encounter the problem, reboot the Mac and launch Console first. Scroll up to examine the messages that occurred immediately before the startup messages. The easiest way to do this is to look in “All Messages” and scroll up, keeping an eye on the timestamps. Once you find the gap preceding your reboot, stop and examine those messages, looking for clues as to what caused the issue.

The next steps are to perform both a PRAM and SMC reset. For instructions on PRAM resets, see Apple’s support article HT1379. For SMC reset instructions, which vary by machine, see article HT3964

Finally, the next time you encounter the problem but before rebooting the computer, see if you can connect to it from another Mac while it’s in its black-screen state. This will require some configuration beforehand.

Remote Login Configuration

Using System Preferences, jot down the instructions on how to remotely connect to your Mac. 

Go to System Preferences > Sharing and enable Remote Login. Once enabled, you’ll see instructions on the right for how to connect to your Mac remotely. Write these down for later. Then, once the machine is in its black-screen state, attempt to connect via Terminal using the instructions you wrote down.

If the connection is successful, you can try to look at the recent logs by typing: 

sudo dmesg 

Here, again, look for any clue as to what’s causing the issue. At the very least, this remote connection will give you an opportunity to power down the Mac properly (as opposed to a forced restart). To do this, type:

sudo shutdown -r now

Hopefully, one of these methods will either solve your problem or point you in the right direction.

This question was originally answered on MGG 365: Building Mac & iOS Apps, Cleaning Mail, Taming Spotlight

About MGG Answers:

Each week Dave Hamilton and John F. Braun provide some great troubleshooting advice to listeners of the Mac Geek Gab podcast. Here with MGG Answers we share some of those tips with the rest of the world!

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Mike Weasner

My MacBook Pro (10.7.2) was locking up waking from sleep from the Login panel.  I found this tip on another web site (MacWorld?).  It seems to have solved that problem.

“When a Mac goes into hibernation it writes the RAM contents to a file called “sleepimage,” and if this file is corrupt then the system may have a hard time accessing it properly. An easy way to fix any problems arising from this is to remove the file by running the following command in the Terminal (supply your password when prompted after entering this command):

sudo rm /private/var/vm/sleepimage

Removing the sleep image is a safe procedure, since the system will just automatically re-create it when it next needs it.”


The article didn’t specify if the user had any drives connected but…

I have a couple of FireWire drives connected. Every so often my Mac hangs when waking up from sleep (screen stays black) or when switching users. If I turn off those FireWire drives the Mac will un-hang and continue as normal. Turn the drives back on, they mount and I’m back in business.


I had the same issue on a ‘08 MacBook. chased it around and around. Finally on the umpteenth web site I found the answer that worked for me.

The issue seems to be a problem with Hibernate Mode. When the system goes to sleep it saves the system status into a file and then powers down. On startup it reads the file and configures your system exactly the way it was before you put it into hibernation. That way if there’s a power interruption you won’t lose any data. The trouble was that the system couldn’t read the file when powering up and would hang. I found the following Terminal commands* resolved the problem for me

sudo pmset -a hibernatemode 0
sudo rm /var/vm/sleepimage

The first switches the system so it will sleep but not save the file status, it just sleeps. The second deletes the existing file you may have on the drive. Since I did this at the beginning of October, my system hasn’t hung once on wakeup. The drawback is that if your system is sleeping and the battery runs dry your system will shut down and you’ll lose any unsaved work. This hasn’t been a problem for me. I figure if I won’t access the system for a few days I should shut the sucker down anyway.  The other neat this about this that the hibernation file is not the size of your session, it’s the size of your RAM so if you, like I do, have 4Gb of RAM the file will be 4Gb in size. Clearing this out freed up some disk space.

*You might want to check the exact command. I couldn’t find the exact site where I found them again. I THINK these are right, they’re close, plus or minus a - or a sudo. YMMV


I have a couple month old MacBook Pro 17”, loaded.  The last several weeks I’ve had the black screen that I could not awaken.  And, could create the problem instantly by closing the cover then opening it right away.  I’d see the desktop for just a moment then it all went black. 

Again.  Tried all the tricks I’ve learned since OS 6.  Nada.

Then, one evening, droopy eyed, I had thought I turned the screen lights down to black and hit the light on buttons on the top left.

That was it!  Every time it went to black screen, on it’s own or closing then immediately opening, all I had to do was hit the F2 key (without the function on) which is the key to brighten your screen.

Haven’t had a problem since.  Still goes black after sitting or closing.  But, it comes right back up with one touch.

Go figure?


Ever tried poking it with a pointy stick ?

Not very technical, but oh so satisfying….


I’ve just spent the morning trying to debug an issue on a system with Java, IE9 and Windows 7.

Do I want to use a pointy stick on the system? Only if it has Louisville Slugger written on the side.


Do I want to use a pointy stick on the system? Only if it has Louisville Slugger written on the side.

That’s more of blunt instrument isn’t it ?


But then so is Windows….

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