You can suspend your notebook running Ubuntu by clicking the Gear icon and choosing Suspend. If you want to suspend from the shell, then the relevant command as described here is:
dbus-send --system --print-reply --dest=org.freedesktop.login1 /org/freedesktop/login1 "org.freedesktop.login1.Manager.Suspend" boolean:true
If you use this frequently, then you can turn it into a script or create a keyboard shortcut for it.
Note: The other methods suggested on the web which use the
powermanagement-interface did not work for me on Ubuntu 14.04.