Can you be a truck driver with one DUI?

It doesn't necessarily disqualify you, but what matters more is the time which has passed since your conviction. It can be a monkey on your back for up to ten years, but that's a bit uncommon. However, within three years of your DUI conviction, you're pretty much untouchable - not just to trucking companies, but for any job which entails operating a motor vehicle. The cost to insure you goes through the roof. But you really need five years between your conviction and the time you apply for a job. Those first five years are the most difficult, but you'll be taken a bit more seriously after that when you apply for a driving job.