With some type of shelter from the rain, sun, snow; and a pail of water, solid footing he cannot dig out of (usually concrete or maybe patio blocks), 24/7. Of course you have to clean poop daily, and ensure that the water is not spilled and changed frequently.
That is a large kennel area and fine for one dog or two.
But, if it is just one dog, then it depends on where you live. If you have kids that will torment the dog, neighbors that will object to lonely barking, a dog that will chew on himself out of boredom, or a neighborhood where dogs are stolen, poisoned or shot, then it may not be safe to keep him out.
Another thought is to have a doggy door to this secure area. An x-pen in the inside of the doggy door will prevent him from jumping all over your couch when he is full of rain or mud. If you do not want the door to go into the house, you can do it to a garage, and keep the whole area behind your house where it is not visible to the road.
Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.