Docker: A lightweight virtualization solution

 A consistent challenge in developing robust software applications is to make them run the same on a machine different than the one on which they are developed. These differences in environments could encompass a number of variables: operating systems, programming language library versions, and hardware such as CPU models.

Traditionally, one approach to dealing with this heterogeneity has been to use  Virtual Machine(VM). While VMs are useful to run applications on diverse hardware and operating systems, they are also limited by being resource-intensive(Figure 2.3): each VM running on a host requires the overhead resources to run a completely separate operating system, along with all the applications of dependencies within the guest system.

However, in some cases this is an unnecessary level of overhead; we do not necessarily need to run an entirely separate operating system, rather than just a consistent environment, including libraries and dependencies within a single operating system. This need for a lightweight framework to specify runtime envirnments prompted the creation of the Docker project for containerization in 2013. In essence, a container is an environment for running an application, including all dependencies and libraries, allowing reproducible deployment of web applications and other programs, such as a database or the computations in a machine learning pipeline. For our use case, we will use it to provide a reproducible Python execution environment (Python language version and libraries) to run the steps in our generative machine learning pipelines.

We will need to have Docker installed for many of the examples that will appear in the rest of this chapter and the projects in this book. For instructions on how to install Docker for your particular operating system, please refer to the directions at (https://docs.docker.com/ install). To verify that you have installed the applications successfully, you should b able to run the following command on your terminal, which will print the available options:

docker run hello-world