I changed username nvidia with something else on tx2. I was able to run xclock after that. But now I am getting this error “Invalid MIT-MAGIC-COOKIE-1 keyError: Can’t open display: :0” after a couple of reboots. can anyone tell me what could be the reason. I manually edited /etc/passwd, /etc/group, /etc/shadow files to change username. is username nvidia required on tx2?