Howto stop the X window on the BBB, from the USB gadget terminal?


I want to try drawing something on the BBB connected LCD (HDMI) using direct writing to the /dev/fb0.
If I do a “cat /dev/urandom > /dev/fb0”, nothing changes on the screen.

Google search helps guessing I need to stop the X window system first, and I should use the “init 3” or “gdm stop” to do so.

If issuing an “init 3”, from the SSH-attached terminal (, then the connection just hangs. (I have no tty0 console yet)
If I use “gdm stop”, then I get the “(gdm-binary WARNING ): Could not acquire name; bailing out” message, and nothing happens.

So, if I just want to draw anything on the LCD screen (to eventually learn, how to draw my image there), how do I try that on my BBB?
Is the /dev/fb0 use the simplest way, and how to get it working (say, to copy file there so that to see the picture change)?
Stop X windows server?
Or any other idea?

Please advise.
Thank you very much. (I am pretty new in this area, sorry if this is a trivial question)