Docker Build Process: Dockerfile to Image to Container
Introduction Docker has revolutionized how we build, ship, and run applications by providing a standardized way to package software with all its dependencies. Understanding the Docker build process is fundamental to modern DevOps practices. This guide visualizes the complete journey from writing a Dockerfile to running a container: Dockerfile Creation: Writing instructions for your application Image Building: Creating a reusable image from the Dockerfile Container Execution: Running instances of your image Multi-Stage Builds: Optimizing image size and security Part 1: The Docker Build Process Flow Complete Build to Run Lifecycle %%{init: {'theme':'dark', 'themeVariables': {'primaryTextColor':'#e5e7eb','secondaryTextColor':'#e5e7eb','tertiaryTextColor':'#e5e7eb','textColor':'#e5e7eb','nodeTextColor':'#e5e7eb','edgeLabelText':'#e5e7eb','clusterTextColor':'#e5e7eb','actorTextColor':'#e5e7eb'}}}%% flowchart TD Start([Developer writes code]) --> CreateDockerfile[Create DockerfileDefine base image,dependencies, commands] CreateDockerfile --> BuildContext[Prepare Build ContextGather files neededfor build] BuildContext --> DockerBuild[Run: docker build -t app:v1 .] DockerBuild --> LayerProcess{Process EachInstruction} LayerProcess --> FROM[FROM instructionPull base image] FROM --> COPY[COPY/ADD instructionsCopy application files] COPY --> RUN[RUN instructionsExecute commandsInstall dependencies] RUN --> ENV[ENV/EXPOSE/WORKDIRSet environment] ENV --> CMD[CMD/ENTRYPOINTDefine startup command] CMD --> CacheCheck{Layer existsin cache?} CacheCheck -->|Yes| UseCache[Use cached layer⚡ Fast build] CacheCheck -->|No| BuildLayer[Build new layer🔨 Execute instruction] UseCache --> NextLayer{Moreinstructions?} BuildLayer --> NextLayer NextLayer -->|Yes| LayerProcess NextLayer -->|No| CreateImage[Create Docker ImageTagged as app:v1Stored in local registry] CreateImage --> DockerRun[Run: docker run -p 8080:8080 app:v1] DockerRun --> CreateContainer[Create Container- Writable layer on top- Network configuration- Volume mounts] CreateContainer --> StartProcess[Start Container ProcessExecute CMD/ENTRYPOINT] StartProcess --> Running[Container Running ✓Application accessibleon port 8080] Running --> Stop{Containerstopped?} Stop -->|No| Running Stop -->|Yes| Cleanup[Container stoppedCan be restartedor removed] style CreateDockerfile fill:#064e3b,stroke:#3b82f6 style CreateImage fill:#1e3a8a,stroke:#3b82f6 style Running fill:#064e3b,stroke:#3b82f6 Image Layer Structure Docker images are built in layers, with each instruction in the Dockerfile creating a new layer: ...