Kubernetes: Up and Running

Chapter 2. Creating and Running Containers

Kubernetes is a platform for creating, deploying, and managing distributed applications. These applications come in many different shapes and sizes, but ultimately, they are all comprised of one or more applications that run on individual machines. These applications accept input, manipulate data, and then return the results. Before we can even consider building a distributed system, we must first consider how to build the application container images that make up the pieces of our distributed system.

Applications are typically comprised of a language runtime, libraries, and your source code. In many cases your application relies on external libraries such as libc and libssl. These external libraries are generally shipped as shared components in the OS that you have installed on a particular machine.

Problems occur when an application developed on a programmer’s laptop has a dependency on a shared library that isn’t available when the program is rolled out to the production OS. Even when the development and production environments share the exact same version of the OS, problems can occur when developers forget to include dependent asset files inside a package that they deploy to production.

A program can only execute successfully if it can be reliably deployed onto the machine where it should run. Too often the state of the art for deployment involves running imperative scripts, which inevitably have twisty and Byzantine failure cases. ...