Containers and Kubernetes: The Essentials

1. Containers, Briefly

A container packages a process together with everything it needs to run: the binary, its libraries, its runtime, and its configuration. All of that is frozen into an image, a build artifact that never changes after it is built. That is what immutable means here.

You do not patch a running image, you build a new one and replace it. Run the same image anywhere and you get the same behavior, so your laptop, CI, and production stop disagreeing about dependency versions. The dependencies travel inside the artifact.

A container is not a virtual machine