Apparently 12.05 has hibernation disabled by default. Rather weird since it still has the option in Power settings to assign Hibernation to a power button. An oversight perhaps? Or an example of issues associated with distributed development?
Anyway, officially there is a method to enable Hibernation on 12.05.
First test if Hibernation is supported:
Open the Terminal by pressing Ctrl+Alt+t or by searching for terminal in the dash.
sudo pm-hibernate[/code] into the terminal and press Enter.
Enter your password when prompted. After you computer turns off, switch it back on. If hibernate doesn't work, check if your swap partition is at least as large as your available RAM.
If the hibernate test works, you can continue to use the sudo pm-hibernate command when you want to hibernate.
You can also enable the hibernate option in the menus. To do that, use your favorite text editor to create /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla.
Add the following to the file and save:[Re-enable hibernate by default]
You can assign hibernation to a button from the KDE Control Module: