Deploy your app with docker and docker-compose - Annex

Why use Docker

• You can easily share the environment with your team.
• You don’t have to install complicated software on your machine.
• Your entire setup is specified in a human-readable yaml syntax.
• All the work you put in your development environment can be reused for production.
• You can run your production setup locally (for small projects). Then deploy using the exact same images on your remote server.

Vocabulary

This section is for those who are not very clear on the distinction between docker images and containers.
I did not find definitions very enlightening, so instead here are some statements that should make sense to you.
They are a bit repetitive as they express only a couple ideas in different ways.

• A docker container is a runtime instance of an image.
• You can run several containers based on a single image at the same time.
• If you’re familiar with object-oriented programming, you can think of an image as a class and of a container as an object.
• docker build creates an image, not a container.
• docker run creates and runs a container based on an image.
• docker push pushes an image to a remote repository called a docker registry.
  Typically dockerhub, but you can push to your own registry or to a cloud provider if you don’t want your images to be public.
• When you make modifications to a container, it does not affect the image (and so future containers will not have your modifications). Here’s a great explanation on the difference between containers and images on stackoverflow.
• When deploying, we don’t have to go and git pull on our server. Pulling the relevant images and running them should be enough. Typically we need only our docker-compose files on the server.