Blars

Overlay file system is NOT what you want, it requires the original media to be readable.   I'd recommend a u-boot that handles net booting (if it exists) loaded to the on-board flash, then a network root and swap if needed.  One system would require real media and the others a network connection to it.

Overlay file system is NOT what you want, it requires the original media to be readable.   I'd recommend a u-boot that handles net booting (if it exists) loaded to the on-board flash, then a network root and swap if needed.  One system would require real media and the others a network connection to it.

Strange HDMI problems can be caused by differing ground levels.  The video signals are differential, but the control ones aren't.  In my case, running an extra ground wire fixed the problem, there was a 2v DC offset between the two.