buttonpower-managementshutdown
So this is pretty simple: when I press the power button whilst the machine is on, it comes up with a menu (of which one of the options is to shutdown)
However, I just want it to just start shutting down once I press the power button without any further interaction!
How do I accomplish this?
Lid Close Action
To set up the Laptop Lid Close Action you have to install Advanced Setting (or the Gnome Tweak Tool). It is in the USC (Ubuntu Software Center) under either tweak or Advanced Settings. If installed press the super button and type in tweak or advanced and choose the Advanced Settings. When it opens choose the shell tab;
Press the arrows and choose you desired on both on AC and on battery;
Default buttons behavior
Install dconf-tools:
sudo apt-get install dconf-tools
Press alt+f2 and open dconf-editor (or in a terminal type dconf-editor)
Navigate to org.gnome.settings-daemon.plugins.power and set your default button-power action there:
On some systems you will also need to mark the item suppress-logout-restart-shutdown.
ACPI is the actual system responsible for handling such power related tasks. Without ACPI support (either software or hardware), you won't be able to listen to the power button event.
For Ubuntu installing the acpid package should be sufficient. This provides the event daemon listening for events such as pressing a power button. It is installed on regular Ubuntu versions, but as you've installed a minimal version, it was omitted.
On a minimal/server installation, the installation can be performed on the command line like any other package:
sudo apt-get install acpid
Best Answer
Yes, that is exactly how I'm running: a light tap on the power button just shuts down the machine!
Just press Ctrl+Alt+T to go to a terminal and type:
Voilà: The power button now powers off the machine!
To be completely honest: the other day I was at a friend and one of her cats ran across my laptop and shut down the machine, so to be avoided near cats! ;-)