In Linux Mint 13, when you click the shutdown button, you will get a window and see options for suspend, restart and shutdown.
The classical Hibernate button is missing!
Inserting the Hibernation button in the log out menu is quite easy. Follow these two steps to get the job done:
1. Create the /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla file.
$ sudo touch /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla
2. Paste the following lines to the newly created /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla file:
[Re-enable hibernate by default]
This is it. If you are a command line user, you can use sudo pm-hibernate to send your Linux box to hibernation.