Here’s an even easier way to turn off HDMI on your Pi-Star image running under Raspbian. If you’re running one of the Pi-Star 4.0 release candidates, the tvservice command may already be installed. You can check by issuing the following command:
If it is installed, just add the HDMI off command to /etc/rc.local.
# Turn off HDMI /usr/bin/tvservice -o
If you’re running Pi-Star 3.x, I learned that you can install tvservice from a .deb package.
sudo apt-get install libraspberrypi-bin
For some reason this did not turn up during my initial searches but was pointed out over in the Pi-Star Forums by Dennis (W1MT).
It also seems that Andy (MM0MWZ) is considering adding a button in the future which would allow turning off HDMI from the web interface.