Typically, the developer writes a set of commands in a file, which is a Docker file. The Docker file mentions the base image also, such as Linux, with any web server or something that is required for the application to run. These base images can be found easily on Docker Hub. After executing the instructions mentioned in the Docker file, the Docker image is built. All the prerequisites, such as copying the application's executable code or configurations, are injected in the Docker image. This is also suppose to be mentioned in the Docker file. Then, this image can be shipped to any environment. These images can also be stored in the repository for future use if is it considered to be a base image for future releases.