headless rpi

I’m setting up some rpi-s which will sometimes boot with mo monitor connected. When they do, the screen size gets set to 640×480. Over Avalanche, that’s not what I need. I cannot change the configured screen size because it says "resources.screenmode.edid0 not found.

I’m guessing there’s something in config.txt I need to change, but I’m struggling to find out what. Setting display_auto_detect=0- doesn’t change the behaviour.

[edit]

I seem to have fixed it. While connected to a monitor, I went into configure-screen and changed the make and model of the monitor, then set the resolution and refresh. It seems to keep these settings when booting without a monitor.

[edit again]

However if the rpi-4 has no monitor, it won’t boot up at all.

[and again edit]

hdmi_force_hotplug=1 in config.txt allows headless booting on a pi model 4

Thank you, Raspberry Pi forums.

If you search on Amazon for ‘Dummy HDMI adapter’ you can use one to pretend to be a monitor with EDID. Only cost a couple of quid.

That would be useful for me too. I bought a RPi 3B, with a PoE+ HAT, with the intention of running it headless. However, it doesn’t power up unless an HDMI lead is connected (but does need to have anything at the other end) or power is applied to the power socket (which is a bit pointless having bought a PoE adapter).

Pis should power up headless with no HDMI connection unless set to read EDID (in which case they wait for small, lemon-soaked paper napkins). Use disable_mode_changes and set a screen resolution manually.