Learning Docker
What are Docker images, containers, and registries?
A Docker image holds the application that you want Docker to run, along with any dependencies.
To create a Docker image, you first create a Dockerfile to describe that application. You then build the Docker image from the Dockerfile. Having created the Docker image, you store it in the Docker registry.
A Docker registry is a system for storing and sharing tagged versions of Docker images. A Docker registry is organized into named repositories. Each repository is associated with a particular version of one or more images.
To run an application held in a Docker image, you have to load the image into a container. You pull the image version associated with a particular repository from the Docker registry and load it into a Docker container.
A Docker container is similar to a directory. A Docker container holds everything that is needed for an application to run, including executable code, runtime environment, system tools, and system libraries. Each container is created from a Docker image. By loading the Docker image into a Docker container, you are wrapping the application inside a complete filesystem that contains everything the application requires. This approach ensures that the application will always run the same, regardless of the environment in which it is running.
