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kubernetes

Kubernetes container orchestration platform. Use for K8s clusters, deployments, pods, services, netw

by franroa|Open Source

Kubernetes Skill

Comprehensive assistance with Kubernetes development, operations, and troubleshooting, generated from official documentation.

When to Use This Skill

This skill should be triggered when users:

Working with Kubernetes Resources

  • Creating, updating, or deleting Kubernetes resources (Pods, Deployments, Services, etc.)
  • Writing or modifying YAML manifests
  • Managing ConfigMaps, Secrets, or PersistentVolumes
  • Working with StatefulSets, DaemonSets, or Jobs

Using kubectl Commands

  • Running kubectl commands or asking about kubectl syntax
  • Querying cluster resources (kubectl get, kubectl describe)
  • Debugging pods or containers (kubectl logs, kubectl exec)
  • Applying or managing configurations (kubectl apply, kubectl rollout)

Cluster Operations

  • Setting up or configuring Kubernetes clusters
  • Managing namespaces and RBAC (Role-Based Access Control)
  • Troubleshooting cluster issues or resource problems
  • Monitoring cluster health or resource usage

Networking & Services

  • Configuring Services (ClusterIP, NodePort, LoadBalancer)
  • Setting up Ingress controllers or network policies
  • Working with DNS resolution in Kubernetes
  • Debugging network connectivity issues

Storage & Configuration

  • Configuring PersistentVolumes and PersistentVolumeClaims
  • Working with StorageClasses
  • Managing application configuration via ConfigMaps and Secrets
  • Setting up encryption at rest

Advanced Topics

  • Implementing custom resource definitions (CRDs)
  • Working with operators or controllers
  • Setting up autoscaling (HPA, VPA)
  • Implementing security policies and admission controllers

Quick Reference

Essential kubectl Commands

Cluster Info & Context

# View cluster information
kubectl cluster-info

# Get current context
kubectl config current-context

# Switch context
kubectl config use-context <context-name>

# Set default namespace
kubectl config set-context --current --namespace=<namespace-name>

Resource Management

# Apply configuration from file or directory
kubectl apply -f <file.yaml>
kubectl apply -f <directory>

# Create resource imperatively
kubectl create deployment nginx --image=nginx

# Delete resources
kubectl delete -f <file.yaml>
kubectl delete pod <pod-name>
kubectl delete pods,services -l <label-key>=<label-value>

Viewing Resources

# List resources
kubectl get pods
kubectl get pods -o wide
kubectl get all -n <namespace>
kubectl get pods --all-namespaces

# View multiple resource types
kubectl get pods,services,deployments

# Describe resource details
kubectl describe pod <pod-name>
kubectl describe node <node-name>

# Watch resources for changes
kubectl get pods --watch

Output Formats

# JSON output
kubectl get pod <pod-name> -o json

# YAML output
kubectl get pod <pod-name> -o yaml

# Custom columns
kubectl get pods -o custom-columns=NAME:.metadata.name,STATUS:.status.phase

# JSONPath
kubectl get pods -o jsonpath='{.items[*].metadata.name}'

Filtering & Selection

# Filter by label
kubectl get pods -l app=nginx
kubectl get pods -l 'env in (prod,staging)'

# Filter by field
kubectl get pods --field-selector=status.phase=Running
kubectl get pods --field-selector=spec.nodeName=<node-name>

# Sort output
kubectl get pods --sort-by=.metadata.creationTimestamp

Debugging & Troubleshooting

# View logs
kubectl logs <pod-name>
kubectl logs <pod-name> -c <container-name>
kubectl logs <pod-name> --follow
kubectl logs <pod-name> --previous

# Execute commands in container
kubectl exec <pod-name> -- <command>
kubectl exec -it <pod-name> -- /bin/bash
kubectl exec <pod-name> -c <container-name> -- <command>

# Port forwarding
kubectl port-forward <pod-name> <local-port>:<remote-port>
kubectl port-forward service/<service-name> <local-port>:<remote-port>

# Copy files
kubectl cp <pod-name>:/path/to/file /local/path
kubectl cp /local/path <pod-name>:/path/to/file

Node Management

# Mark node as unschedulable
kubectl cordon <node-name>

# Drain node for maintenance
kubectl drain <node-name> --ignore-daemonsets

# Mark node as schedulable
kubectl uncordon <node-name>

# View node resources
kubectl top nodes
kubectl top pods

Deployments & Scaling

# Create deployment
kubectl create deployment <name> --image=<image>

# Scale deployment
kubectl scale deployment <name> --replicas=<count>

# Autoscale deployment
kubectl autoscale deployment <name> --min=<min> --max=<max> --cpu-percent=<percent>

# Update image
kubectl set image deployment/<name> <container>=<new-image>

# View rollout status
kubectl rollout status deployment/<name>

# View rollout history
kubectl rollout history deployment/<name>

# Rollback deployment
kubectl rollout undo deployment/<name>
kubectl rollout undo deployment/<name> --to-revision=<revision>

Services & Networking

# Expose deployment as service
kubectl expose deployment <name> --port=<port> --target-port=<target-port>

# Create service
kubectl create service clusterip <name> --tcp=<port>:<target-port>

# View endpoints
kubectl get endpoints

# Test DNS resolution
kubectl run -it --rm debug --image=busybox --restart=Never -- nslookup <service-name>

Configuration & Secrets

# Create ConfigMap from literal
kubectl create configmap <name> --from-literal=<key>=<value>

# Create ConfigMap from file
kubectl create configmap <name> --from-file=<path>

# Create Secret
kubectl create secret generic <name> --from-literal=<key>=<value>
kubectl create secret tls <name> --cert=<cert-file> --key=<key-file>

# View Secret data (base64 encoded)
kubectl get secret <name> -o jsonpath='{.data}'

Labels & Annotations

# Add label
kubectl label pod <pod-name> <key>=<value>

# Remove label
kubectl label pod <pod-name> <key>-

# Update label
kubectl label pod <pod-name> <key>=<value> --overwrite

# Add annotation
kubectl annotate pod <pod-name> <key>=<value>

Resource Quotas & Limits

# View resource usage
kubectl describe resourcequota -n <namespace>
kubectl describe limitrange -n <namespace>

# View pod resource requests/limits
kubectl get pods -o custom-columns=NAME:.metadata.name,MEMORY:.spec.containers[*].resources.requests.memory,CPU:.spec.containers[*].resources.requests.cpu

Advanced Operations

# Edit resource
kubectl edit deployment <name>

# Patch resource
kubectl patch deployment <name> -p '{"spec":{"replicas":3}}'

# Replace resource
kubectl replace -f <file.yaml>

# Diff changes before applying
kubectl diff -f <file.yaml>

# Explain resource fields
kubectl explain pod
kubectl explain pod.spec.containers

# View API resources
kubectl api-resources
kubectl api-versions

Common Use Cases

1. Deploying an Application

Create Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.21
        ports:
        - containerPort: 80

Apply and verify:

kubectl apply -f deployment.yaml
kubectl get deployments
kubectl get pods -l app=nginx
kubectl describe deployment nginx-deployment

2. Exposing an Application

Create Service:

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80
  type: LoadBalancer

Apply and test:

kubectl apply -f service.yaml
kubectl get service nginx-service
kubectl describe service nginx-service

3. Debugging a Pod

# Check pod status
kubectl get pod <pod-name> -o wide

# View detailed information
kubectl describe pod <pod-name>

# Check logs
kubectl logs <pod-name>
kubectl logs <pod-name> --previous  # Previous container logs

# Get shell access
kubectl exec -it <pod-name> -- /bin/sh

# Check events
kubectl get events --sort-by=.metadata.creationTimestamp

# Check resource usage
kubectl top pod <pod-name>

4. Working with ConfigMaps and Secrets

Create ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  database_url: "postgres://localhost:5432"
  log_level: "info"

Use in Pod:

spec:
  containers:
  - name: app
    image: myapp:latest
    envFrom:
    - configMapRef:
        name: app-config

Create and use Secret:

# Create secret
kubectl create secret generic db-secret \
  --from-literal=username=admin \
  --from-literal=password=secret123

# Use in pod
env:
- name: DB_USER
  valueFrom:
    secretKeyRef:
      name: db-secret
      key: username

5. Setting Up Persistent Storage

PersistentVolumeClaim:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: app-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: standard

Use in Deployment:

spec:
  containers:
  - name: app
    volumeMounts:
    - name: data
      mountPath: /data
  volumes:
  - name: data
    persistentVolumeClaim:
      claimName: app-pvc

6. Implementing Health Checks

spec:
  containers:
  - name: app
    image: myapp:latest
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
      initialDelaySeconds: 30
      periodSeconds: 10
    readinessProbe:
      httpGet:
        path: /ready
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 5

7. Managing Updates with Rolling Updates

# Update image
kubectl set image deployment/nginx nginx=nginx:1.22

# Watch rollout
kubectl rollout status deployment/nginx

# Pause rollout
kubectl rollout pause deployment/nginx

# Resume rollout
kubectl rollout resume deployment/nginx

# Rollback if needed
kubectl rollout undo deployment/nginx

8. Working with Namespaces

# Create namespace
kubectl create namespace dev

# List all namespaces
kubectl get namespaces

# Set default namespace for context
kubectl config set-context --current --namespace=dev

# Delete namespace (careful!)
kubectl delete namespace dev

# Get resources across all namespaces
kubectl get pods --all-namespaces

9. DNS Resolution in Kubernetes

Service DNS format:

<service-name>.<namespace>.svc.cluster.local

Example:

# From within a pod in the same namespace
curl http://my-service

# From a different namespace
curl http://my-service.production.svc.cluster.local

# Test DNS resolution
kubectl run -it --rm debug --image=busybox --restart=Never -- nslookup my-service

10. Checking Connectivity

# Test port connectivity from within cluster
kubectl run -it --rm netcat --image=busybox --restart=Never -- nc -zv <service-name> <port>

# Test from specific pod
kubectl exec -it <pod-name> -- nc -zv <host> <port>

# Check if load balancer is accessible
nc -zv -w 2 <LOAD_BALANCER_IP> <PORT>

Best Practices

Manifest Organization

  • Use declarative configurations (YAML files)
  • Store manifests in version control
  • Organize by namespace or application
  • Use Kustomize or Helm for complex deployments

Resource Management

  • Always set resource requests and limits
  • Use namespaces to organize resources
  • Apply labels consistently for filtering
  • Use annotations for metadata

Security

  • Follow principle of least privilege with RBAC
  • Use Secrets for sensitive data
  • Enable encryption at rest
  • Implement NetworkPolicies
  • Scan images for vulnerabilities

High Availability

  • Run multiple replicas for production apps
  • Use PodDisruptionBudgets
  • Configure liveness and readiness probes
  • Implement proper health checks

Monitoring & Logging

  • Aggregate logs centrally
  • Monitor resource usage
  • Set up alerts for critical metrics
  • Use kubectl top for quick checks

Troubleshooting Guide

Pod Issues

Pod stuck in Pending:

kubectl describe pod <pod-name>
# Check: Events, resource availability, PVC binding

Pod in CrashLoopBackOff:

kubectl logs <pod-name>
kubectl logs <pod-name> --previous
kubectl describe pod <pod-name>
# Check: Application errors, liveness probe failures

ImagePullBackOff:

kubectl describe pod <pod-name>
# Check: Image name, registry credentials, network access

Service Issues

Service not reachable:

kubectl get endpoints <service-name>
kubectl describe service <service-name>
# Check: Selector labels match pods, endpoints exist

DNS not resolving:

kubectl get pods -n kube-system -l k8s-app=kube-dns
kubectl run -it --rm debug --image=busybox -- nslookup <service>
# Check: CoreDNS pods running, service exists

Node Issues

Node NotReady:

kubectl describe node <node-name>
kubectl get pods -n kube-system
# Check: kubelet logs, network connectivity, resource pressure

Version Information

This skill was automatically generated from official Kubernetes documentation and includes information accurate for Kubernetes 1.25+. While most concepts remain consistent across versions, always verify specific API versions and features for your cluster version:

kubectl version
kubectl api-versions
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