Mastering kubectl: From Basic to Advanced Commands

Kubernetes is a powerful container orchestration platform, and kubectl is the command-line tool that allows you to interact with your Kubernetes cluster. Whether you’re just getting started or looking to dive deeper into advanced operations, this guide covers kubectl commands from basic to advanced, complete with examples and detailed explanations.

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1. Introduction to kubectl 🤔

kubectl is the primary command-line interface for Kubernetes. It enables you to deploy applications, inspect and manage cluster resources, and view logs. Mastering kubectl is essential for efficient cluster management.

Key Benefits:

• Ease of Use: Command-line interface for quick operations.
• Powerful Resource Management: Create, update, and delete Kubernetes resources.
• Debugging & Troubleshooting: Access logs, events, and detailed resource information.

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2. Basic kubectl Commands

A. Viewing Cluster Information

• Get Cluster Info:
  Displays the Kubernetes master and services. kubectl cluster-info
• List Nodes:
  Shows all nodes in the cluster. kubectl get nodes

B. Managing Pods

• List Pods:
  Retrieve a list of all Pods in the default namespace. kubectl get pods
• Describe a Pod:
  Provides detailed information about a specific Pod. kubectl describe pod <pod-name>
• View Pod Logs:
  Stream logs from a Pod. kubectl logs <pod-name>

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3. Intermediate kubectl Commands

A. Working with Deployments

• List Deployments: kubectl get deployments
• Create a Deployment:
  Deploy an NGINX application. kubectl create deployment nginx-deployment --image=nginx:latest
• Update a Deployment:
  Update the image for the deployment. kubectl set image deployment/nginx-deployment nginx=nginx:1.19
• Scale a Deployment:
  Increase or decrease the number of replicas. kubectl scale deployment/nginx-deployment --replicas=5

B. Working with Services

• List Services: kubectl get services
• Expose a Deployment as a Service:
  Create a service to expose the deployment on port 80. kubectl expose deployment nginx-deployment --port=80 --target-port=80 --type=LoadBalancer

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4. Advanced kubectl Commands

A. Advanced Resource Management

• Apply Configurations:
  Use declarative configuration with YAML files. kubectl apply -f deployment.yaml Example deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: myapp-deployment spec: replicas: 3 selector: matchLabels: app: myapp template: metadata: labels: app: myapp spec: containers: - name: myapp image: myapp:latest ports: - containerPort: 80
• Delete Resources: kubectl delete -f deployment.yaml or delete a specific resource kubectl delete pod <pod-name>

B. Debugging and Troubleshooting

• Execute a Command in a Running Pod:
  Open an interactive shell inside a container. kubectl exec -it <pod-name> -- /bin/bash
• Port Forwarding:
  Forward a local port to a port on a Pod. kubectl port-forward pod/<pod-name> 8080:80
• Rollout Status:
  Check the status of a deployment rollout. kubectl rollout status deployment/nginx-deployment
• Rollout Undo:
  Roll back to a previous version if needed. kubectl rollout undo deployment/nginx-deployment

C. Using Labels and Selectors

• Label a Resource:
  Add a label to a Pod. kubectl label pod <pod-name> env=production
• Query by Label:
  List all resources with a specific label. kubectl get pods -l env=production

D. Resource Monitoring and Custom Metrics

• Top Command:
  Display resource usage for nodes or pods. kubectl top nodes kubectl top pods
• Custom Metrics:
  Integrate with tools like Prometheus to expose custom metrics and use them for auto-scaling.

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5. Best Practices for Using kubectl

• Declarative Configurations:
  Always use YAML files for managing resources to ensure version control and reproducibility.
• Regular Monitoring:
  Use kubectl top and monitoring tools to keep track of resource usage.
• Labeling:
  Consistently label resources for easy management and filtering.
• Automate with Scripts:
  Automate routine tasks using shell scripts and CI/CD pipelines.
• Test in Staging:
  Validate changes in a non-production environment before applying them to live clusters.

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6. Visual Overview

Below is a simplified diagram illustrating the flow of Kubernetes resource management with kubectl:

flowchart TD
    A[Write YAML Configurations]
    B[Apply Configurations (kubectl apply)]
    C[Manage Resources (kubectl get, describe, label)]
    D[Scale & Update (kubectl scale, set image)]
    E[Debug & Troubleshoot (kubectl exec, logs)]

Diagram: The workflow from writing configurations to managing, scaling, and debugging Kubernetes resources.

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