www.petholidayfinder.co.uk/ekmps/shops/pfhf751/images/stake-out-spike-ground-tie-ring-for-dog-lead-385-p.jpg and a long lead/rope
Most site require you not to let your dog run free,
Apart from a dog cocking its leg on tents (which will make you deeply unpopular), dogs that are not use to being so close to livestock deserve their owners to be careful and not allow them to get into trouble. and if you let them run free, you might miss a poo, making all K9 owners unpopular, it's also good form not to allow your dog to poo in camping fields, so take them for a walk, first thing, and pick up,
Most people don't want to interact with other people's dogs, so unless yours is trained and will stay sat when told, keep it on a lead when on a site.
let it sleep in the boot of your car, it will be fine, leave the window open on the opposite side of the wind direction ,
mine usually sleep in a line outside(their choice) the tents, if it rains too hard, they might move into the porch of my tent.
but mine will not move unless instructed by a handler, and are use to sheep.
make sure your dog knows the word "enough" so if it does think it is it's place to bark, you can instantly shut it up.