I upgraded to version 0.8 of Ghost over the weekend. I am pretty proud of myself as it was all command line on Linux.
It would have been a half hour job if I had just followed all of the instructions here. Unfortunately, when they say follow all the steps exactly, they mean follow all the steps exactly.
It was true in first grade and its still true today: following instructions is hard.
Anyway, I didn't blow away the core directory I just copied the new one over the top and that led to weird problems down the road.
Fortunately, the fix was easy. Just follow all the steps exactly and voila! It works.