Cloud & DevOps Essentials

Virtualization vs Containers

What a container actually is: namespaced processes on a shared kernel — and why that changed deployment.

docker build -t app:v1 .      # daemon builds layers, caches each instruction
docker run -d -p 8080:80 app:v1  # -d detached, -p host:container port map
docker push registry.example.com/app:v1

# final argv = ["python", "server.py", "--port", "8080"]
ENTRYPOINT ["python", "server.py"]
CMD ["--port", "8080"]

# ---- build stage ----
FROM node:20-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
# ---- runtime stage ----
FROM node:20-alpine
WORKDIR /app
COPY --from=build /app/dist ./dist
COPY package*.json ./
RUN npm ci --omit=dev
CMD ["node", "dist/server.js"]

Container Orchestration: Kubernetes

Control plane vs worker nodes, and the Pod → ReplicaSet → Deployment → Service → Ingress chain.

Control Plane                      Worker Node xN
+---------------+   schedule      +------------------------+
| API Server    | --------------> | kubelet  (pod agent)   |
| Scheduler     |                 | kube-proxy (rules)     |
| etcd (state)  |                 | Container runtime      |
| Controller Mgr|                 |  + Pod [app, sidecar]  |
+---------------+                 +------------------------+

resources:
  requests: { cpu: "100m", memory: "128Mi" }
  limits:   { cpu: "500m", memory: "256Mi" }
readinessProbe:
  httpGet: { path: /healthz, port: 8080 }
  initialDelaySeconds: 5

Cloud Fundamentals: AWS / Azure / GCP parity

The four pillars — compute, storage, networking, identity — mapped across the big three clouds.

{
  "Effect": "Allow",
  "Action": ["s3:GetObject"],
  "Resource": "arn:aws:s3:::reports-bucket/public/*"
}

CI/CD Pipelines

Build → test → deploy as code: GitHub Actions syntax, artifacts, secrets, and deployment strategies.

push → [build] → [test] → [scan] → [build image] → push registry
                                              ↓ environments
                                    dev (auto) → staging (auto) → prod (approval gate)

name: ci
on: { push: { branches: [main] }, pull_request: {} }
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: npm }
      - run: npm ci
      - run: npm test -- --coverage
      - run: npm run build

Observability & Reliability (SRE)

Metrics vs logs vs traces, Prometheus/Grafana/ELK, and SLA/SLO/SLI with error budgets.