Phase 8 — Container Strategy

Understanding how containers work in a k3s cluster.

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Runtime

✔ k3s uses containerd (not Docker)
✔ Docker images still work — OCI-compatible
✔ No Docker daemon required on nodes

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Building Images

Build on your local machine or in CI:

docker build -t my-app:v1.0 .
docker tag my-app:v1.0 registry.local/my-app:v1.0
docker push registry.local/my-app:v1.0

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What You Can Deploy

✔ Node.js apps
✔ Python / FastAPI services
✔ AI/ML inference services
✔ SaaS applications
✔ Databases (PostgreSQL, Redis, etc.)

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Registry Options

Option	Use Case
Docker Hub	Public images
GitLab Registry	Private images + CI integration
Harbor	Self-hosted, enterprise features
Local registry	Air-gapped / development

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Sample Deployment Manifest

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-app
          image: registry.local/my-app:v1.0
          ports:
            - containerPort: 3000