This simple tutorial will show you how to easily get back hibernate option in system menu with 3 commands in Ubuntu 12.04.
Hibernate has been disabled in Ubuntu 12.04 by default. ppa:vanhoof/policykit-d-p-hibernate-enabled contains a rebuild of policykit-desktop-privileges that re-enables hibernate, also fixes hibernation not wake up problem(if any).
Open terminal via Ctrl+Alt+T, and execute 3 commands:
sudo add-apt-repository ppa:vanhoof/policykit-d-p-hibernate-enabled
sudo apt-get update
sudo apt-get install policykit-desktop-privileges
Restart your machine, and see effect!