Does a 4 ft. chain link fence need concrete footings for the posts?
I understand that it would be difficult to dig holes for a concrete footing for your posts. Depending where you are located and the soil types, you could drive the posts in and still have a stable fence. If you are in an area with frost in the ground, I would encourage you to set them at least 3 feet deep if the soil is stable and compacted. The basic rule of thumb is to bury at least a third of the posts, but half the length is even better if you can do it.