What is the difference between a Docker image and a container?

docker docker-container docker-image
bibstha picture bibstha · May 19, 2014 · Viewed 347.3k times · Source

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.

What is a container?

Answer

Thomas Uhrig picture Thomas Uhrig · May 19, 2014

An instance of an image is called a container. You have an image, which is a set of layers as you describe. If you start this image, you have a running container of this image. You can have many running containers of the same image.

You can see all your images with docker images whereas you can see your running containers with docker ps (and you can see all containers with docker ps -a).

So a running instance of an image is a container.

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