Kubernetes Day 1: Understanding Docker, Containers, and Linux Foundations

Docker is a containerization platform that packages an application along with its base OS and required dependencies into a portable image, which is then run as a container. Containers are fundamentally Linux-based, and on Windows they operate through WSL, the Windows Subsystem for Linux, using a Linux kernel feature called cgroups. Docker Engine is open-source, but Docker Desktop requires a paid license; alternatives like Podman also exist in this space. A container image is essentially a lightweight snapshot of an OS or application — for example, a functional Ubuntu environment can be spun up from an image as small as 40MB. Multiple such images are stored and managed in a registry, and basic Docker commands allow users to pull images, run interactive containers, and manage their lifecycle.