The Starlost was a sci-fi television series devised by writer Harlan Ellison and broadcast in 1973 on CTV in Canada and syndicated to local stations in the United States. I'm reasonably certain it never saw the light of day on this side of the Atlantic although with so many regional channels back then I stand to be corrected if any one knows better.
The show's setting was a huge colony spacecraft called The Ark, which had gone off-course. Many of the descendants of the original crew and colonists were unaware of this and that they were even aboard a spaceship.
The series experienced a number of production difficulties right from the start and Ellison ended up disowning it before the first episode had even aired. 16 episode were made in total before the plug was finally pulled.