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'''Docker and Kubernetes''' are the two most important technologies in modern server infrastructure. Docker provides lightweight containerization, while Kubernetes (K8s) orchestrates containers at scale. Together, they form the foundation of [[Cloud Computing Explained: From Basics to Advanced|cloud-native]] application deployment.

== What Are Containers? ==

Containers are lightweight, isolated environments that package an application with all its dependencies. Unlike virtual machines, containers share the host OS kernel, making them:

* '''Faster to start''' — seconds vs minutes for VMs
* '''More resource-efficient''' — no separate OS per instance
* '''Portable''' — runs identically on any system with Docker installed
* '''Reproducible''' — same environment in development, testing, and production

== Docker Basics ==

=== Installing Docker ===

On Ubuntu/Debian:

curl -fsSL https://get.docker.com | sh
sudo usermod -aG docker $USER

=== Key Concepts ===

* '''Image''' — a read-only template containing the application and dependencies
* '''Container''' — a running instance of an image
* '''Dockerfile''' — instructions for building an image
* '''Docker Hub''' — public registry for sharing images

=== Essential Docker Commands ===

docker pull nginx # download an image
docker run -d -p 80:80 nginx # run container in background
docker ps # list running containers
docker logs container_name # view container logs
docker exec -it container_name bash # open shell in container
docker stop container_name # stop container
docker rm container_name # remove container

=== Dockerfile Example ===

FROM python:3.11-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
EXPOSE 8000
CMD ["python", "app.py"]

Build and run:

docker build -t myapp .
docker run -d -p 8000:8000 myapp

== Docker Compose ==

For multi-container applications, use Docker Compose:

version: '3.8'
services:
web:
build: .
ports:
- "80:80"
db:
image: postgres:15
environment:
POSTGRES_PASSWORD: secret
volumes:
- pgdata:/var/lib/postgresql/data
volumes:
pgdata:

Run with: <code>docker compose up -d</code>

== Kubernetes Introduction ==

Kubernetes (K8s) manages containers across multiple servers. It handles:

* '''Scheduling''' — decides which node runs each container
* '''Scaling''' — automatically adjusts the number of container replicas
* '''Self-healing''' — restarts failed containers, replaces unresponsive nodes
* '''Load balancing''' — distributes traffic across container instances
* '''Rolling updates''' — deploys new versions with zero downtime

=== Key Kubernetes Concepts ===

* '''Pod''' — smallest deployable unit, contains one or more containers
* '''Service''' — stable network endpoint for a set of pods
* '''Deployment''' — manages pod replicas and updates
* '''Namespace''' — logical isolation within a cluster
* '''Ingress''' — HTTP routing and load balancing

=== When to Use Kubernetes ===

Kubernetes adds complexity. It is worth using when:

* You run 10+ microservices
* You need automatic scaling
* High availability is critical
* You have a team to manage the infrastructure

For simpler setups, Docker Compose on a single [[VPS vs Dedicated Server: Complete Comparison|VPS or dedicated server]] is often sufficient.

== See Also ==

* [[Introduction to Containerization with Docker and Kubernetes]]
* [[Building a Scalable Cloud Infrastructure]]
* [[Cloud Computing Explained: From Basics to Advanced]]

[[Category:Cloud Computing]]

Docker and Kubernetes: Getting Started - Revision history

Admin: New guide article