I install Linux on computers and add to the base installation some other programs. This computer then is sold to a customer as a larger instrument. Now, I am looking for a way to implement some kind licence for this computer so the user can use it for a year and then he would need to "renew" the licence. It is not my intention to lock the whole computer , blocking or deleting some folders should be enough. The only way I could think of was to setup a cron job that deletes my programs, or a second way would be to set the user account to expire after a year.
But I give the computer with sudo privilages so the above solutions wouldn't be 100% safe. It is not my intention to encrypt any code, I just want block the possibility to execute certain programs. Is there a way or a program that would "licence the computer" ? Ideally it should be invisible to the user. After one year the program stops working and "he doesn't know why."