Docker Containerization Basics

The problem containers solve

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“It works on my machine” — environment drift is an ops nightmare. Containers package the app with its runtime into an image that runs anywhere.

Core concepts

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• Image: a read-only template made of layers
• Container: a running instance of an image; start, stop, remove
• Volume: persists container data
• Dockerfile: a declarative recipe for building images

Common commands

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docker build -t my-app .
docker run -d -p 8080:80 my-app
docker compose up -d

Best practices

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• Use multi-stage builds to shrink images
• Run processes in the foreground for easy log collection
• Pass secrets via env vars or secrets, never bake them in

Summary

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Docker lowers delivery cost and aligns local with production. Mastering it is the first step on the cloud-native path.