Why I always disable “Wake On Lid Open” on my MacBooks

I have a loaner MacBook for an upcoming project. It’s a gradual move-in process. First I run Software Update, and then I start installing the apps I need. Inevitably, a few weeks’ worth of music and movies go into the iTunes library and some useful Automator workflows are copied and installed as plug-ins.

On and on. There’s one last thing that I might not get to right away, but always happens…and usually after a lot of cursing.

I go into Terminal and type

sudo pmset -a lidwake 0

…and then I enter my admin password. This disables the MacBook’s “Wake from sleep when lid is opened” behavior.

“Why the bloody hell would _anybody_ want to disable that?” you might ask. “What, you often open your MacBook just to check your makeup in the glossy screen?”

It’s a safety thing. Way, _way_ too frequently I’ve picked up my laptop bag and it felt…warm. I unzipped it and heared a screaming fan. At some unguessable point in the recent past, the MacBook got jostled just enough to twitch the screen sensor and it woke up.

Inside a sealed bag whose thick padding acted as thermal insulation. Result: a white-hot $1500 computer. That can’t be good. If there are any weak points in the hardware, that sort of abuse will cook ’em right into a hardware failure.

Worse: when this sort of thing happens and I pull the machine out, I prepare myself for percolator-like noises signifying a head crash. If I had KNOWN that my MacBook was awake, I certainly wouldn’t have run for the train. And when I caught my train, I wouldn’t have simply dropped my bag on the seat in exhaustion. Even when it’s a padded case and a padded seat, you should _never_ drop a running MacBook. Because — see if you can follow this, Mr. Wake On Lid Open feature — IF THE HARD DRIVE IS SPINNING ALL OF ITS DATA WILL GET CREAMED by the jostling and bouncing.

Okay? I’ve only had one unrecoverable drive crash in my life, and it happened when I accidentally dropped my MacBook a whole three-quarters of an inch while it was waking from sleep.

Ideally, “Disable Wake On Lid Open” would be a system pref instead of something that can only be done via the command line. But if this were an ideal world, the normal bumps and jostles that a notebook experiences in transit wouldn’t be enough to wake the machine.

At least Prefs has a “sleep hard drive whenever possible” option. It’s intended to conserve the battery but it probably protects your data, too. The next time you slide your MacBook out of the way a little to make room for your beverage and wind up bumping it right into a wall, think about that option. Ideally, you’ll be thinking “Boy, I’m glad I turned it on; there’s an excellent chance that the drive heads were safely parked when that happened.”

Posted via email from ihnatko’s posterous

28 thoughts on “Why I always disable “Wake On Lid Open” on my MacBooks”

  1. Yup, that’s one I always enable as well. The other one I always enable is “verbose boot/shutdown”, which is:
    “sudo nvram boot-args=-v”. This is the same as holding down command-V during boot. It takes away the pretty blue spinner screen, but being able to see if something is stuck during booting vs just taking a long time is very handy.

  2. I could have sworn “wake on lid open” used to be an optional setting in System Preferences, but apparently not anymore.

  3. When I first read this tip I figured it must be a Leopard or Intel only setting, thankfully it also works on my Tiger PowerBook. And I completely agree about spinning down the HDD, SMS or not. Great tips Andy, looks like today’s bandwidth wasn’t a celestial waste after all. :)

  4. It has happened a few times to me a well! However, I disagree with your point about jostling the computer creaming the hard-drives. That’s the whole reason the MBP have motion sensors. If they sense too much movement, they disengage the drive heads to avoid damage.

  5. Hi. Nice tip that I’m not sure I would want to use, but definately worth knowing.
    Another thing is that you should look in the RSS for this article – it looks like something strange is happening when you’re posting by mail with Posterous.
    Cheers

  6. I’m willing to give this a try with my MBP, but most of the time it sits on the side of my desk with the lid closed and attached to an external monitor. With this change, will I be unable to wake and work? I have enough problems getting it to sleep as it is. I click on Sleep, it nods off for a moment, but then pops back awake within moments about 50% of the time.

  7. I never knew that jostling the computer could trip the switch and wake it up. Always thought, it was kind of “locked” in place until the lid was opened. That would explain the couple of times I found a hot machine in my bag!! I will assuredly try this.

    On another topic – Are you still doing the Sun Times column? Have not seen one for a bit.

  8. A coworker’s Mac actually killed itself in exactly this way. Since the lack of better heat controls was considered a firmware problem, Apple repaired it. And repaired it again. And repaired it again. The result never worked quite right again…

    …and was eventually replaced by Apple Canada with a newer model for a pittance.

  9. Having had this happen myriad times, its related to lidwake, but also to the point in time when you move the machine after closing the lid.

    That is, without disabling the lidwake:
    Shut the lid and immediately put the machine in your bag == high likelihood of a white-hot machine.
    Shut the lid and wait for the sleep led to being fading (ie. the contents of RAM have finished being copied to the HD) == very low likelihood of a white-hot machine.

    So I always make sure to leave my machine for the requisite 30 seconds (or so) and check the LED before putting it in my bag. Inconvenient, yes, but safe.

  10. I toggle between sleep and hibernate modes depending on if I’m at home or traveling (moving the laptop in and out of its bag a lot). When traveling I set the power mode to “hibernate” with:

    sudo pmset -a hibernatemode 1

    Which means it can’t wake when jostled in the bag. It takes a few more seconds to wake up afterwards, but that short wait is well worth having all the batter life and no white-hot laptop and screaming fan.

    For those who aren’t command line fans, Patrick Stein has a great Preference Pane item called SmartSleep that can do this switch for you: http://www.jinx.de/SmartSleep.html.

  11. I have also run into white-hot macbook a couple of times…what I found though, is that it has nothing to do with opening/closing the lid, but the sequence of detaching peripherals (display, mouse, etc).

    I would have the problem when I disconnected any USB devices AFTER closing the lid and disconnecting external displays. Since I have started disconnecting USB devices first, I have not encountered the problem.

    Hope this helps someone!

  12. I’ve also had this occur (laptop bag) – however I find it isn’t due to the lid opening but rather due to a BlueTooth event (e.g. bluetooth mouse) waking the macbook pro.

  13. Like Rodney above, I haven’t had mine wake up by itself like this but once I forgot the nano-sized USB receiver of my Logitech mouse in the port when packing my bags. Although wireless, mouse click will wake up the machine. Had I had eggs with me, I would’ve cooked them on the lid. Luckily, nothing was broken and it came back to life after waiting for it to cool down and giving it some power. Super scary, still.

  14. Great tip. 2 questions.
    1. How do you you wake it up after you apply this command?

    2. How do you undo this command?

  15. Anyone having problems getting this to work in Snow Leopard? I was able to run the command, but apparently after a reboot, it goes back. I just opened my lid and the MacBook Pro woke up.

  16. This is definitely something that I want to do. Especially with my unibody MBP, since the lid often yawns open–anyone else have that problem?

    I got as far in Terminal as entering my password at the prompt but no matter what I do it won’t let me type it in…

    Any ideas?

    Thanks

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