I forgot a dot there. It should read:

$ docker build -t my_image:2.0 .

It wasn’t meant as a tutorial though, so it doesn’t contain every detail of the steps needed to do something in docker. It was meant to help you conceptually understand docker. It was kind of meant for people who hear buzz about Docker and wonder what exactly it is. Or who started trying it out but who get confused by how all the different concepts relate to each other.

Here I wrote a bit more step by step guide of using docker for desktop development. But I intend to write a more detailed guide later.