For simplicity I keep the scripts in my profile folder. i.e. /home/osmc/ I added "/bin/sh /home/osmc/activateHdmi &" (without quotes) to /etc/rc.local to run it.

I know this is a very old thread but I'm sure someone will find this useful. I created two scripts that together allow headless booting and hotplugging the HDMI to different monitors as needed. I never intend to use the composite so it is effectively disabled by these scripts. I'm running a Pi3 as a...