I have a friend who parole violated him he's been in county jail for a month and no one will say anything about why they have a parole hold on him or anything else. How long can they keep him with out him knowing what they have him on

A parole violation is considered a serious offense, one which carries no bond. The only one that knows why your friend is being held is your friend's parole officer and your friend. They can hold him for months and months without cause before the next step.

What happens next is your friend will go before the original sentencing judge to explain why he violated. The judge can hold him for the balance of the original sentence if they choose. It's not a good thing to get caught up in... it's always better to follow the rules of their release and not jump back into the system where you have zero control over your own future.