Using docker cloud can result in a black box experience should something go wrong.

This is especially the case when you provision the node from the cloud UI.

Building a stack with Docker/Dockercloud -AuthorisedKeys however, can get you SSH access, to poke around inside.

authorizedkeys:
  image: dockercloud/authorizedkeys
  deployment_strategy: every_node
  autodestroy: always
  environment:
    - "AUTHORIZED_KEYS=ssh-rsa h38Fh4w89fdlx-s...304KJbhn45=="
  volumes:
    - /root:/user:rw

Ensure you also open up port 22 on your VM

Once inside, you can take a peek at various logs using a couple of methods.

docker logs containerName

cat /var/log/upstart/dockercloud-agent.log

cat /var/log/dockercloud/docker.log