sudo gedit /var/lib/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla
Copy and paste below lines into the file and save it.
[Re-enable hibernate by default in upower] Identity=unix-user:* Action=org.freedesktop.upower.hibernate ResultActive=yes [Re-enable hibernate by default in logind] Identity=unix-user:* Action=org.freedesktop.login1.hibernate ResultActive=yes
Source: http://ubuntuhandbook.org/index.php/2013/10/enable-hibernation-ubuntu-13-10/
