I type docker.io version, and get:
Client version: 0.9.1
Go version (client): go1.2.1
Git commit (client): 3600720
Server version: 0.9.1
Git commit (server): 3600720
Go version (server): go1.2.1
Last stable version: 0.11.1, please update docker
I follow that with an apt-get update, then either: apt-get upgrade, or apt-get upgrade docker.io, but all it gives me is:
docker.io is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
I'm running Ubuntu 14.04 (trusty) 64bit server.
EDIT: I think I used a script in this Post comment to install docker (since it purported to allow me to just type docker instead of docker.io)