DOCKER IMAGES & LAYERS A STEP-BY-STEP TUTORIAL WHAT IS A DOCKER IMAGE -> A Docker image is a read-only template used to create containers -> It contains application code, runtime, libraries, and dependencies -> Images are portable and can run consistently across environments -> Built using a Dockerfile WHAT ARE DOCKER LAYERS -> Docker images are composed of multiple layers -> Each layer represents a change or instruction -> Layers are stacked to form the final image -> All layers are immutable once created HOW DOCKER IMAGES ARE BUILT -> Docker reads the Dockerfile -> Executes instructions one by one -> Each instruction creates a new layer -> Layers are combined into a final image COMMON DOCKERFILE INSTRUCTIONS AND LAYERS -> FROM -> Defines the base image -> Creates the first layer -> RUN -> Executes commands -> Adds a new layer with changes -> COPY / ADD -> Transfers files into the image -> Creates a new layer -> ENV -> Sets environment variables -> Adds metadata layer -> WORKDIR -> Sets working directory -> Affects subsequent instructions -> CMD / ENTRYPOINT -> Defines container startup behavior -> Final layer configuration LAYERED FILESYSTEM EXPLAINED -> Each layer is read-only -> Layers are stacked on top of each other -> Docker merges them into a single unified filesystem -> Containers add a writable layer on top WRITABLE CONTAINER LAYER -> Created when a container starts -> Stores runtime changes -> Includes logs, temporary files, and modifications -> Removed when the container is deleted DOCKER LAYER CACHING -> Docker caches each layer during build -> If nothing changes, cached layers are reused -> Improves build performance -> Changing one layer invalidates subsequent layers LAYER REUSE AND SHARING -> Multiple images can share common layers -> Saves disk space and bandwidth -> Faster image pulls and builds -> Encourages reuse of base images WHY DOCKER LAYERS MATTER -> Efficient storage management -> Faster build times -> Faster deployment and scaling -> Easy updates by rebuilding only changed layers BEST PRACTICES FOR USING LAYERS -> Use minimal base images -> Combine RUN instructions where possible -> Order instructions for optimal caching -> Avoid unnecessary files in the image -> Use multi-stage builds for cleaner images FINAL SUMMARY -> Docker images are built from layered instructions -> Each layer is immutable and reusable -> Containers run on top of these layers with a writable layer -> Efficient layering improves speed, storage, and scalability LEARN DOCKER IN DEPTH -> Grab the Docker Mastery eBook -> codewithdhanian.gumroad.com/…