Hello again, First of all, I'd like to thank everyone that helped me on my other thread, about adapting a software to run as an activity on XO. Thanks to you all, I was able to do it. But now, I'm facing another problem regarding the permissions olpc user has to access diferent dispositives on XO. The software I adapted uses the USB port to communicate with an external module, to which it will send a compiled code. It's an graphical programming tool, with the purpose of robotics teaching. The problem is, since OLPC user doesn't have enough permissions to access the ports, we can't send the compiled code to the external module, unless we manually change the permissions to do so. So, my question is, is there any way to do it without having to do it manually for every machine we install or activity in ? Just in case, the device our activity is trying to access is /dev/ttyACM0 Using ls -l /dev/ttyACM0 we see that the its access permission is uucp while the group of our activity is olpc. Using chmod o=rw /dev/ttyACM0 solves the problem. Thanks again