Q: What would cause my truck to put out white smoke from exhaust.

Hello. I can tell you exactly what causes the white smoke to be emitted from your exhaust upon starting the engine. This would be due to your engine burning oil. The engine will burn oil when oil reaches the combustion chamber. The combustion chamber is the air space between the bottom of the cylinder head and the top of each piston. The oil will be able to get into the combustion chamber when the valve guide seals (above the piston within the cylinder head) or the piston rings (connected to the piston and below the combustion chamber) start to show excessive wear. This will allow oil to flow right past and get into the combustion chamber and the oil gets burned right along with the fuel. The more likely cause in your case would be the valve guide seals due to the fact that it happens on start up only. Oil will pool up on top of the valve guide seals when the engine is shut down. Unfortunately, the engine would need to be disassembled in order to replace the valve guide seals. To verify the correct repair, I would recommend enlisting the assistance of a qualified professional to diagnose the smoke issue in person.