Containerised Builds

Containers have revolutionised CI/CD by providing consistent, isolated, and reproducible build environments. This lesson covers Docker in CI/CD, multi-stage builds, image registries, and best practices for containerised pipelines.

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Why Containers in CI/CD?

Without containers:

Developer's machine: Node 20, npm 10, Python 3.12, Go 1.22
CI server: Node 18, npm 9, Python 3.9, Go 1.20
Production: Node 20, npm 10, Python 3.11, Go 1.22
→ "Works on my machine" problems

With containers:

Developer:  docker run node:20-alpine npm test   ✓
CI server:  docker run node:20-alpine npm test   ✓
Production: docker run node:20-alpine npm start  ✓
→ Same environment everywhere

Benefits

Benefit	Description
Consistency	Same environment from dev to production
Isolation	Builds do not interfere with each other
Reproducibility	Pin exact image versions for deterministic builds
Speed	Pre-built images with dependencies already installed
Portability	Run on any CI platform that supports Docker

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Docker Fundamentals for CI/CD

Key Concepts