What is the difference between a Docker image and

Question

When using Docker, we start with a base image. We boot it up, create changes and those changes are saved in layers forming another image.

So eventually I have an image for my PostgreSQL instance and an image for my web application, changes to which keep on being persisted.

So the question is: What is a container?

Answer 1

In short:

Container is a division (virtual) in a kernel which shares a common OS and runs an image (Docker image).

A container is a self-sustainable application that will have packages and all the necessary dependencies together to run the code.

Answer 2

For a dummy programming analogy, you can think of Docker has a abstract ImageFactory which holds ImageFactories they come from store.

Then once you want to create an app out of that ImageFactory, you will have a new container, and you can modify it as you want. DotNetImageFactory will be immutable, because it acts as a abstract factory class, where it only delivers instances you desire.

IContainer newDotNetApp = ImageFactory.DotNetImageFactory.CreateNew(appOptions);
newDotNetApp.ChangeDescription("I am making changes on this instance");
newDotNetApp.Run();