Enable hibernate in ubuntu 12.04

Hibernate is disable by default in ubuntu 12.04 because of a bug. Follow below instructions to enable hibernate back.

Get the terminal and copy & paste this code
$gedit /var/lib/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla

then it will prompt a new file in gedit and do changes like below

[Re-enable hibernate]
Identity=unix-user:*
Action=org.freedesktop.upower.hibernate
ResultActive=yes

Restart computer and hibernate will be back.