Learn DOCKERFILE with Real Code Examples

Dockerfiles automate image creation, ensuring consistent environments across development, testing, and production.

Each instruction in a Dockerfile creates a layer in the resulting image, improving caching and build efficiency.

Supports specifying base images, copying files, installing packages, and configuring entry points.

Enables reproducible and versioned container images.

Integrates with CI/CD pipelines for automated image building and deployment.

FROM - specify base image

RUN - execute commands during image build

COPY / ADD - add files and directories

ENV - define environment variables

CMD / ENTRYPOINT - default runtime commands

Image - immutable snapshot built from Dockerfile

Container - running instance of an image

Layer - filesystem snapshot for caching

Registry - storage for images (Docker Hub, ECR, GCR)

Build context - directory used for building Docker images

Dockerfile - main build instructions

Application source code directories

Configuration files (env, JSON, YAML, etc.)

Optional .dockerignore to exclude files

Scripts for entrypoints or initialization

Write Dockerfile with necessary instructions

Place application and dependency files in build context

Build image using `docker build` command

Tag and push image to a registry if needed

Run containers with `docker run` for testing or deployment

Beginner: Containerize a simple Node.js or Python app

Intermediate: Add environment variables and configuration

Advanced: Multi-stage builds to optimize image size

Expert: Integrate build with CI/CD pipelines

Architect: Orchestrate multiple containers with Compose/Kubernetes

Dockerfile vs VM provisioning: Docker is lightweight and faster to start

Dockerfile vs Docker Compose: Compose orchestrates multiple containers, Dockerfile builds individual images

Dockerfile vs Podmanfile: Similar, Podman is rootless and daemonless

Dockerfile vs Kubernetes manifests: Dockerfile builds image, manifests deploy containers

Dockerfile vs VM images: Images are smaller, portable, and reproducible

2013 - Docker initial release

2013–2015 - Dockerfile syntax standardized

2016–2018 - Multi-stage builds introduced

2019–2021 - BuildKit and improved caching

2022–2025 - Enhanced security scanning and cross-platform builds

Dockerfile - text file with instructions to build an image

Image - immutable filesystem created from Dockerfile

Container - running instance of an image

Layer - incremental snapshot created by each instruction

Build context - folder containing files for building image