How to turn off the display via the command line?

I think you are looking for

xset dpms force off

However, you need to make sure that your acpi is enabled. You can check this with

cat /proc/acpi/info

Another option could be

setterm -powersave powerdown

I'm running Ubuntu Server without X on a 2007 MacBook Pro. The display is sleeping by itself but won't reactivate when a key is pressed on the keyboard. At this point my fix is to use vbetool. Install using apt-get:

sudo apt-get install vbetool

Then use to turn display on via SSH from a different machine:

sudo vbetool dpms on

Or off:

sudo vbetool dpms off

I have made a unity launcher to turn off the LCD

sudo apt-get install --no-install-recommends gnome-panel

gnome-desktop-item-edit ~/Desktop/ --create-new

It will open a small windows. Enter the following:

Name: turnofflcd

Command: gnome-screensaver-command --lock && sleep 2s && xset dpms force off

You can also choose an icon by clicking the icon on the left .

For more on making launcher see http://www.ubuntugeek.com/how-to-create-desktop-launchers-in-ubuntu-11-10oneiric.html.

(sleep 10; xset dpms force suspend) & xdg-screensaver lock

This starts the screen saver in locked mode and then puts your display in standby. Ubuntu Mate 15.10