Docker and Kubernetes FAQ: Most Common Questions Answered

TL;DR: Docker is a containerization engine that packages your applications. Kubernetes is an orchestration platform that deploys, scales, and maintains them in production. Both are complementary. According to CNCF Annual Survey (2025) (source), 82% of organizations use Kubernetes in production. This FAQ covers the 10 most searched questions on the topic in 2026.

What is the difference between Docker and Kubernetes? This is the question thousands of IT professionals ask every month, in French and English. This FAQ gathers concrete answers to the most frequent questions about these two technologies, with practical examples and updated data. To explore containerization and Docker best practices, see our dedicated guide.

What is the difference between Docker and Kubernetes?

Docker is a containerization engine that packages an application and its dependencies into a portable image. Kubernetes is an orchestration platform that manages the lifecycle of these containers on a cluster of machines.

For a detailed comparison with performance benchmarks, see our article Kubernetes vs Docker: understanding essential differences.

Key takeaway: Docker and Kubernetes are not competitors. Docker builds containers, Kubernetes orchestrates them. You need both in a cloud-native stack.

Can you use Kubernetes without Docker?

Yes. Since Kubernetes 1.24 (May 2022), direct Docker support (dockershim) was removed (official announcement). Kubernetes now uses runtimes conforming to the Container Runtime Interface (CRI). containerd v1.7+ is the default runtime on most Kubernetes distributions in 2026, including EKS, GKE, and AKS.

# Check your nodes' runtime
kubectl get nodes -o wide
# The CONTAINER-RUNTIME column shows containerd://1.7.x

# Check cluster version
kubectl version --short
# Server Version: v1.32.x

Remember that your Docker images remain compatible: the OCI format is standard. Only the Docker daemon is no longer needed cluster-side. The migration from Docker Compose to Kubernetes details transition steps.

Is Docker Compose enough for production?

No. Docker Compose is a local development tool that defines multi-container services via a docker-compose.yml file. It provides neither high availability, nor automatic scaling, nor rolling updates, nor self-healing.

For production, Kubernetes brings:

• Auto-scaling: HorizontalPodAutoscaler adjusts replica count based on CPU/memory load
• Self-healing: A crashed pod is automatically recreated by the ReplicaSet
• Rolling updates: Progressive deployment without service interruption via kubectl rollout
• Service discovery: Internal DNS resolution between services via CoreDNS

Migrate progressively with Kompose to convert your Compose files. Our guide on migration to Kubernetes from Docker Compose, VMs or monoliths details each step.

Key takeaway: Docker Compose suits local development and testing. For production with more than 3 services, adopt Kubernetes or a managed service (EKS, GKE, AKS).

What certifications validate Docker and Kubernetes skills?

Three Kubernetes certifications are recognized by the industry, all issued by the Linux Foundation and CNCF:

1. CKA (Certified Kubernetes Administrator): Cluster administration, networking, storage, troubleshooting. Prepared by LFS458 (4 days).
2. CKAD (Certified Kubernetes Application Developer): Application deployment, ConfigMaps, Probes, Jobs. Prepared by LFD459 (3 days).
3. CKS (Certified Kubernetes Security Specialist): Cluster security, admission controllers, runtime security. Prepared by LFS460 (4 days).

Certifications are valid 2 years and recognized worldwide. Explore all three exam details on our Kubernetes CKA CKAD CKS Certifications page.

The Docker Certified Associate (DCA) certification is offered by Mirantis. Docker skills are also evaluated in all three Kubernetes certifications above.

How to optimize a Docker image for Kubernetes?

An optimized Docker image reduces pull time, attack surface, and memory consumption of your pods. Apply these five rules:

# 1. Use a minimal base image
FROM cgr.dev/chainguard/python:latest

# 2. Multi-stage build to separate build and runtime
FROM node:22 AS builder
WORKDIR /app
COPY . .
RUN npm ci && npm run build

FROM node:22-slim
COPY --from=builder /app/dist ./dist

# 3. Single process per container
CMD ["node", "dist/server.js"]

According to the Chainguard State of Container Security 2025 report, distroless images contain on average 90% fewer CVEs than Debian or Ubuntu-based images. Follow our step-by-step guide to optimize a Dockerfile for Kubernetes for a complete protocol.

What is the difference between Docker Swarm and Kubernetes for orchestration?

Docker Swarm is Docker's native orchestrator. It's simpler to configure but offers fewer features than Kubernetes. In 2026, Docker Swarm represents a marginal share of production deployments.

For a complete benchmark including ECS and Nomad, see the Kubernetes vs Docker Swarm, ECS and Nomad comparison. Our Docker Swarm to Kubernetes migration experience presents a concrete case with timeline and metrics.

Key takeaway: Docker Swarm remains viable for small internal projects. For any critical or multi-cloud deployment, Kubernetes is the industry standard in 2026.

What Docker and Kubernetes commands should I know first?

Focus on these essential commands to work effectively with both tools:

# Docker: container lifecycle
docker build -t my-app:v1 .
docker run -d -p 8080:80 my-app:v1
docker logs <container-id>
docker exec -it <container-id> /bin/sh

# Kubernetes: common operations (kubectl 1.32)
kubectl apply -f deployment.yaml
kubectl get pods -n production
kubectl describe pod <pod-name>
kubectl logs <pod-name> -f --tail=100
kubectl rollout status deployment/my-app

For a complete reference to keep handy, download our Docker and Kubernetes cheat sheet: essential commands. Also see the kubectl cheatsheet for debugging.

How to get started with Docker and Kubernetes from scratch?

Start with Docker before tackling Kubernetes. The recommended path in 2026:

1. Week 1-2: Install Docker Desktop, containerize an existing application
2. Week 3-4: Write multi-stage Dockerfiles, use Docker Compose for local development
3. Week 5-8: Deploy a local Kubernetes cluster with kind or minikube
4. Week 9-12: Prepare for a certification (CKA or CKAD based on your profile)

Get started with our Docker and Kubernetes quick start guide. For structured upskilling, the Kubernetes Fundamentals training offered by SFEIR Institute covers Docker and Kubernetes in 1 day (7h) with hands-on exercises. Also see our page on installing Kubernetes locally with minikube, kind and k3d.

How to solve the most common Docker and Kubernetes errors?

The five most frequent errors and their solutions:

For a complete troubleshooting guide with decision trees, see our page debugging a CrashLoopBackOff pod and the guide solving Kubernetes deployment errors.

How to fund Docker and Kubernetes training?

Check your eligibility in three steps:

1. Identify your OPCO (ATLAS for digital, AFDAS for consulting)
2. Submit the funding request 30 days before training starts
3. Provide the training agreement signed by SFEIR Institute

SFEIR group training organizations (SFEIR SAS, SFEIR-EST) are Qualiopi certified for training actions. Contact your OPCO to explore funding possibilities.

Training is available throughout France, notably in Paris, Bordeaux, and Lille. See the Kubernetes Training thematic map to visualize all available paths.

More questions about Docker and Kubernetes?

Contact SFEIR Institute to get personalized answers to your technical or administrative questions. Our trainers, CKA/CKAD/CKS certified and active in production, guide you to the path suited to your level and goals.

• Just starting? Kubernetes Fundamentals: 1 day to discover Docker and Kubernetes
• Targeting administration? LFS458 Kubernetes Administration: 4 days to administer production clusters
• Developing on Kubernetes? LFD459 Kubernetes for Developers: 3 days to deploy cloud-native applications
• Securing your clusters? LFS460 Kubernetes Security: 4 days on security best practices

Discover all our Kubernetes trainings and choose your path.