If it were me, I would just down all my interent in my house before turning my computer on. Then I would clone my drive. Following that I would call Apple to see if there is a timeout limitation to the command or if it could be canceled. Then, only then would I turn on internet and turn on my computer. The worse case, all attempts to cancel the comman failed and you have to clone back from your back up drive. Best case, you know have a cloned copy of your drive for future back up needs.