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Play with Docker Classroom

Containers and images

A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state.

An image is a read-only template with instructions for creating a Docker container. A Docker registry stores Docker images.

Docker Hub (https://hub.docker.com/) is a public registry that anyone can use, and Docker is configured to look for images on Docker Hub by default; millions of images are available.

There are three different ways to use containers. These include:

• To run a single task: This could be a shell script or a custom app.
• Interactively: This connects you to the container similar to the way you SSH into a remote server.
• In the background: For long-running services like websites and databases.

In the following we will see examples of all three ways to use containers

Run a single task “Hello World”

docker container run hello-world

[<https://hub.docker.com/_/hello-world>](<https://hub.docker.com/_/hello-world>)

Images can have multiple versions. For example you could pull a specific version of ubuntu image as follows:

docker pull ubuntu:12.04