Keep screen completely, absolutely, off

I am currently experimenting with coreos in a small home cluster.

All the machines have an HDMI output and, for the time being, they are all connected to my main monitor (mainly because I am redeploying 5 times a day… I’m still experimenting).

My problem is my monitor won’t turn off. I have set the consoleblank kernel arg to a non-zero value, I have created a custom unit file making use of setterm, nothing works!

I mean, consoleblank does trigger the blanking but does not turn off the screen whereas setterm does power the screen off but then turn it on when my monitor scans the other inputs before really going off. Currently, machine A goes off after 10 seconds, my monitor scans the other inputs, Machine B turns on and off after 10 seconds, my monitor scans the other inputs, Machine C turns on and off after 10 seconds, etc. (and yes, it cycles back…)

So my question is: is there a way to completely utterly disable video output unless the keyboard is actually used?

(Hardware contraptions with servomotors to plug and unplug the cables when the keyboard is in use won’t be considered… :stuck_out_tongue: And I can’t set my monitor to manual, there is no option for it)

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