Hi @sr007, looking at your picture you are just logged into the DRM console. xrandr needs Xorg to be up and running, so you’ll need to start your window manager.
This will take up a bunch of memory space, in your application do you need a full X11 based window manager?
If we just need to resize the DRM console, it would be best to pass the video parameter from /boot/uEnv.txt
Open /boot/uEnv.txt find the “un-commented” cmdline variable and add this to the end:
video=HDMI-A-1:1024x768@60e
Regards,