I’ve seen some people ask about making the Docker command docker.io on Ubuntu work like it does in the examples: docker. I found this inconvenient too, but fortunately, Ubuntu and Debian have had a solution to this for a long time, it’s called alternatives. In this particular case, there is already an Ubuntu package called docker which is why they are trying to de-conflict executable names by using docker.io in the first place. Ironically, the original docker package doesn’t even contain an executable named docker. Or at least it doesn’t as of Ubuntu 14.04.

$ dpkg -L docker

I don’t fully understand the Ubuntu/Debian policies on package and executable naming, but perhaps the use of docker.io is unnecessary. Regardless, those of us who aren’t concerned with building packages can either simply soft link the docker.io command to docker or create an alternative:

# Making a link
sudo ln /usr/bin/docker.io /usr/bin/docker
# Using Alternatives
sudo update-alternatives --install /usr/bin/docker docker \
  /usr/bin/docker.io 1