Simply taking your family pet and throwing it in an RV and 'expecting' it to behave like it did at home? Doesn't work. 'He' does NOT know that that new thing is supposed to be so much fun. To him it's a brand new building that is NOT his home and he certainly does not want to be left alone in this new strange building.
==IF==, Rv'ers would take a few days out of their time after purchasing an RV to socialize/familiarize their dog with the RV, there would be no barking dogs left inside an RV at CG's.
Park the RV in your driveway and set it up.
Bring the dog and let him explore the RV 'with' you for a few minutes thru out the day.
Sleep overnight in the RV one or two nights with the dog.
Then start taking him out to the RV and leave and stand right outside so he can see you. If barking starts right then and there correct him and assure him you are right outside.
Feed him in the RV for a couple of days while you sit with him, then feed him and take a walk outside. Going to the mailbox? Take the dog with and put him in the RV with a dog treat. Pick up him on the way back. etc.
Bottom line, like anything else related to dog, you have to 'socialize them' whether it be to other people, kids, other dogs, etc.......you HAVE to take the time to socialize him to your RV also.
If this sounds like a waste of your time and a pain to do?
Just think what it is going to be like when you hit the road RV'ing and your family can NOT go any where after you get to the CG?
A few days of socializing the dog to an RV before heading out = a lifetime of fun RV'ing.:C