Docker attach is supposed to give you a bash shell

But I have found on some containers that it just hangs when you run it:

docker attach 54b38600e152

But this command works for me (and apparently allows multiple shells to attach)

docker exec -i -t 54b38600e152 bash

Update: It seems that later versions of docker allow the attach and you get a bash prompt as root. But if you exit the container dies. To detach and keep the container running use CTRL + P, CTRL + Q