Properly speaking, a container in this context is a reproducible disk image of a Linux-based environment that contains all the files and dependencies necessary to run some piece of software. Container technology is built into all modern Linux OS kernels and supports projects like Docker, Kubernetes, rkt, among others.
Even though container technology is 100% Linux, Docker distributes a Toolbox that contains everything you need to run a container image on any Mac, Linux, or Windows system. With a well-assembled container image, we can package up all the code in this book and all of its dependencies so that any reader, anywhere, can have a perfectly configured development environment. (Under the hood, the Docker Toolbox runs a tiny Linux Virtual Machine, on which the containers will actually run. But it’s almost 100% transparent for ordinary use.)
For all these reasons, I recommend using Docker to work through the exercises in this book; however, there are a few wrinkles we’ll have to work through also. In particular, many of Docker’s excellent security features, which provide total isolation between the running container and the host machine’s network and filesystem, can cause problems when we want to interact with a running program. But we’ll see how to resolve these issues shortly.