How to enable hibernation in 15.04?

Solution 1:

1. Create the following file: /etc/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla

2. Copy / paste the following content into it:

   [Enable hibernate by default in upower]
   Identity=unix-user:*
   Action=org.freedesktop.upower.hibernate
   ResultActive=yes
   
   [Enable hibernate by default in logind]
   Identity=unix-user:*
   Action=org.freedesktop.login1.hibernate;org.freedesktop.login1.handle-hibernate-key;org.freedesktop.login1;org.freedesktop.login1.hibernate-multiple-sessions;org.freedesktop.login1.hibernate-ignore-inhibit
   ResultActive=yes
   

3. Log out and check that you can see the hibernate menu item on the login screen, do the same once you logged in.

The reason the above manual step needs to be done is that they seem to have disabled hibernate by default in Ubuntu 15.04.

Solution 2:

The answer given by Jinesh Choksi to create the file /etc/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla doesn't seem to work for me, when I resume hibernation, it just performs a normal boot. The best option I've found is the classic pm-hibernate, which works with no issues:

sudo pm-hibernate

You also have the option of a hybrid suspend/hibernate. From the man pages:

pm-suspend-hybrid
    Hybrid-suspend is the process where the system does everything it needs to hibernate, but suspends instead of shutting down. This means
    that your computer can wake up quicker than for normal hibernation if you do not run out of power, and you can resume even if you run
    out of power. s2both(8) is an hybrid-suspend implementation.