i solved this in a simpler way.

I made a python script which generates a "AltF4" keyboard event:

#!/usr/bin/python import keyboard keyboard.send('Alt+f4')

(it requires the pyhon keyboard library. If you don't have it on your system, then give the command "pip install keyboard" to install it.

and added a line to call this script in /opt/retropie/configs/all/autostart.sh:

emulationstation #auto sudo python /opt/altf4/altf4.py

for me it's solved. I still think functionality like this should be included in the normal retropie build. This prevents a security issue (someone can press alt-f4 in emulation station and will have access to the system with sudo rights with entering any password)

@Mark_tml_fe Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first

@Dochartaigh I just did a quick read of your progress (or lack of same and I really feel your pain!!) and I may have missed something but was just wondering if you have tried a USB2 port and reader to burn the image and a larger microSD card (maybe 32gig)? I would just load the basic image to see if ran OK, then add ROMs one at a time till it fails. Please don't think I am patronizing you or your effort.