Disable Safe Sleep Mode In Lion


Safe Sleep, a feature of the Mac OS that writes the contents of the RAM to a file called sleepimage on the SSD/ disk to protect active data in the event the MacBook loses all power. Disabling safe sleep can free up precious storage space particularly when working with MacBook Airs and their SSD drives (128 GB and 256 GB).

Turning Off Safe Sleep

Open the Terminal (in Applications > Utilities), then type the following command:

sudo pmset -a hibernatemode 0

Press Enter. You’ll be prompted to enter your password. Do so, then press Enter again.

Next, type this command:

sudo rm /var/vm/sleepimage


If you decide to re-enable Safe Sleep, just replace the first Terminal command with this one:

sudo pmset -a hibernatemode 3

Changing the “0” to a “3” turns Safe Sleep back on, where data is saved during Sleep to both the RAM and the disk/SSD. Reboot after the change.

Disabling Safe Sleep doesn’t mean that you can’t put your Mac to sleep; closing the lid still puts it in a low-power state. It just means that if you lose all battery power while sleeping, you’ll lose your active data.