Some time back I disabled hibernation mode on my macbook pro to save space on the drive. This is because hibernation required creation of a sleepimage file which was 2 Gb in size. Recently I stumbled across an article which again listed how to turn this off.

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

I decided to turn hibernation back on after this trip down memory lane, and so, issued the following command: sudo pmset hibernatemode 1