Docker, released in 2013, has ignited enormous interest in Linux container technology by making it dramatically easier to package, distribute, and run applications in isolated environments. While containerization concepts are not new, Docker's tooling and ecosystem have brought containers from a niche technology to a mainstream deployment model in record time.
What Makes Docker Different
Docker packages an application and all its dependencies into a portable image that runs consistently on any Linux system with the Docker engine installed. Unlike virtual machines, containers share the host's kernel and start in milliseconds, making them far more resource-efficient. A server that can run a dozen virtual machines might comfortably run hundreds of containers.
The Docker Hub registry provides a vast library of pre-built images for popular software. Pull an official Nginx, MySQL, or Redis image and have it running in seconds. Build custom images using a Dockerfile that defines the base image, installed packages, configuration files, and startup command. The layered image filesystem caches intermediate build steps, making subsequent builds very fast.
For hosting and operations teams, Docker promises consistent environments from development through production. Developers build and test against the same container image that will run in production, eliminating the "it works on my machine" problem. However, production container deployments require orchestration tools for scheduling, service discovery, networking, and health management. Projects like Docker Compose and the emerging Kubernetes project aim to address these operational requirements.