Figure Out Why Your Mac Won’t Go To Sleep [OS X Tips]

Figure Out Why Your Mac Won’t Go To Sleep [OS X Tips]

It can be seriously annoying when you want your Mac to sleep but it wants to stay up late, playing video games, eating cheese doodles and generally not doing “lights-out.” Wait, maybe that’s my kids. Anyway, when it’s your Mac that won’t get to sleep, today’s tip should help you get to the bottom of it.

I keep my Mac Mini at my bedroom desk, and it’s always spinning up and waking up when I don’t want it to, so maybe today’s tip is more about me than you, but that’s ok, right?

Launch Terminal, found in the Utilities folder, which itself is in the Applications folder on your Macintosh’s hard drive. Once launched, type or paste the following command in:

pmset -g assertions

The first bit of output will show you the status of PreventSystemSleep and PreventUserIdleSystemsSleep – if either one is shown to have a status of the number 1, that means it is currently triggered, keeping your system awake.

The second part shows which processes “own” the assertions that are enabled, so check down there to see what’s keeping your Mac up. If you don’t at first figure out what process is being named, you can launch Activity Monitor, also in the Utilities folder, and visually see what process is being named.

You will then be able to quit the program, kill the offending process, or at least know why your Mac is awake when you really want it snoring away like the gentle sleeping, er, Lion, that it is.

  • meletis3d

    Thats cool, but it shows me a processes that doesn’t exist in my activity monitor :S
    ExternalMedia named: “com.apple.powermanagement.externalmediamounted”

  • SamAltenberger

    Thanks so much! Because of this, I figured out why my macbook would kill it’s own battery if I left it out! It was Internet Sharing, from a long time ago when I was sharing my WiFi through Ethernet, and forgot to turn it off.

  • Stuka_UK

    Thanks!

About the author

Rob LeFebvreAnchorage, Alaska-based freelance writer and editor Rob LeFebvre has contributed to various tech, gaming and iOS sites, including 148Apps, Creative Screenwriting, Shelf-Awareness, VentureBeat, and Paste Magazine. Feel free to find Rob on Twitter @roblef, and send him a cookie once in a while; he'll really appreciate it.

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