Alright, so I just went through the install process on a fresh CentOS 7 EC2. Everything seems to have gone smoothly, although I do notice a something weird:
$ ./launcher start app
which: no docker.io in (/sbin:/bin:/usr/sbin:/usr/bin)
6dd44a3a02af
Nothing to do, your container has already started!
Anyway, this instance seems to be suffering the same problem. So I’m guessing this means it must be something to do with my security group settings. Although as far as I can tell, they are all as they should be.