Introduction
Kubernetes, also known as K8s, is a powerful open-source system for automating the deployment, scaling, and management of containerized applications. Whether you are new to Kubernetes or an experienced user, mastering its commands is crucial for efficiently managing your clusters. This article provides a comprehensive guide to Kubernetes commands, organized from beginner to advanced levels.
๐ฏ Key Concepts
Before we dive into the commands, let's review some fundamental Kubernetes concepts:
- Pod: The smallest and simplest Kubernetes object, representing a single instance of a running process in your cluster.
- Node: A worker machine in Kubernetes, which can be a virtual or a physical machine.
- Namespace: A way to divide cluster resources between multiple users.
- Deployment: A higher-level abstraction that manages a replicated application, ensuring that a specified number of replicas are running.
- Service: An abstraction that defines a logical set of pods and a policy by which to access them.
- ConfigMap and Secret: Mechanisms to inject configuration data into your applications.
๐ Beginner Commands
1. Cluster Information
Get Cluster Info
kubectl cluster-info Displays the address of the Kubernetes master and services running in the cluster.
Get Nodes
kubectl get nodes Lists all nodes in the cluster.
2. Namespace Management
List Namespaces
kubectl get namespaces Displays all namespaces in the cluster.
Create Namespace
kubectl create namespace my-namespace Creates a new namespace.
Delete Namespace
kubectl delete namespace my-namespace Deletes a specified namespace.
3. Pod Management
List Pods
kubectl get pods kubectl get pods -n my-namespace Lists all pods in the default namespace or a specified namespace.
Describe Pod
kubectl describe pod my-pod Displays detailed information about a specific pod.
Create Pod
kubectl run my-pod --image=nginx Creates a new pod running the specified container image.
Delete Pod
kubectl delete pod my-pod Deletes a specified pod.
4. Deployment Management
List Deployments
kubectl get deployments kubectl get deployments -n my-namespace Lists all deployments in the default namespace or a specified namespace.
Create Deployment
kubectl create deployment my-deployment --image=nginx Creates a new deployment with the specified container image.
Delete Deployment
kubectl delete deployment my-deployment Deletes a specified deployment.
5. Service Management
List Services
kubectl get services kubectl get services -n my-namespace Lists all services in the default namespace or a specified namespace.
Create Service
kubectl expose deployment my-deployment --type=LoadBalancer --name=my-service Creates a new service to expose a deployment.
Delete Service
kubectl delete service my-service Deletes a specified service.
๐ Intermediate Commands
1. ConfigMap and Secret Management
List ConfigMaps
kubectl get configmaps kubectl get configmaps -n my-namespace Lists all ConfigMaps in the default namespace or a specified namespace.
Create ConfigMap
kubectl create configmap my-config --from-literal=key1=value1 --from-literal=key2=value2 Creates a new ConfigMap from literal values.
List Secrets
kubectl get secrets kubectl get secrets -n my-namespace Lists all secrets in the default namespace or a specified namespace.
Create Secret
kubectl create secret generic my-secret --from-literal=username=admin --from-literal=password=secret Creates a new secret from literal values.
2. Scaling Applications
Scale Deployment
kubectl scale deployment my-deployment --replicas=3 Scales a deployment to the specified number of replicas.
3. Updating Applications
Update Deployment
kubectl set image deployment/my-deployment nginx=nginx:1.19.1 Updates the container image in a deployment.
Rollout Status
kubectl rollout status deployment/my-deployment Displays the rollout status of a deployment.
Rollback Deployment
kubectl rollout undo deployment/my-deployment Rolls back a deployment to the previous revision.
4. Monitoring and Logging
View Pod Logs
kubectl logs my-pod Displays the logs of a specified pod.
View Previous Pod Logs
kubectl logs my-pod --previous Displays the logs of a previous instance of a specified pod.
Get Events
kubectl get events kubectl get events -n my-namespace Lists all events in the default namespace or a specified namespace.
5. Resource Management
Describe Node
kubectl describe node my-node Displays detailed information about a specified node.
Label Nodes
kubectl label nodes my-node disktype=ssd Adds a label to a node.
Annotate Resources
kubectl annotate pod my-pod description="my example pod" Adds an annotation to a resource.
6. Network Policies
Create Network Policy
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: allow-nginx namespace: my-namespace spec: podSelector: matchLabels: app: nginx policyTypes: - Ingress ingress: - from: - podSelector: matchLabels: app: frontend Apply the network policy:
kubectl apply -f network-policy.yaml ๐ง Advanced Commands
1. Advanced Pod Management
Debug Pod
kubectl debug my-pod --image=busybox --target=my-container Debugs a running pod by creating a new debugging container in the pod.
Port Forwarding
kubectl port-forward my-pod 8080:80 Forwards a local port to a port on a pod.
2. Advanced Node Management
Cordon Node
kubectl cordon my-node Marks a node as unschedulable.
Drain Node
kubectl drain my-node --ignore-daemonsets Safely evicts all pods from a node before maintenance.
Uncordon Node
kubectl uncordon my-node Marks a node as schedulable.
3. Resource Quotas and Limits
Create Resource Quota
apiVersion: v1 kind: ResourceQuota metadata: name: compute-resources namespace: my-namespace spec: hard: pods: "10" requests.cpu: "4" requests.memory: 16Gi limits.cpu: "10" limits.memory: 32Gi Apply the resource quota:
kubectl apply -f resource-quota.yaml 4. Custom Resources and CRDs
Create Custom Resource Definition
apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com versions: - name: v1 served: true storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string image: type: string replicas: type: integer scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct Apply the CRD:
kubectl apply -f crd.yaml Create Custom Resource
apiVersion: stable.example.com/v1 kind: CronTab metadata: name: my-new-cron-object namespace: my-namespace spec: cronSpec: "* * * * */5" image: my-cron-image replicas: 3 Apply the custom resource:
kubectl apply -f custom-resource.yaml 5. Helm for Kubernetes Package Management
Install Helm
Follow the installation instructions for Helm from the official Helm website.
Add Helm Repository
helm repo add stable https://charts.helm.sh/stable Install Helm Chart
helm install my-release stable/nginx List Helm Releases
helm list Upgrade Helm Release
helm upgrade my-release stable/nginx Uninstall Helm Release
helm uninstall my-release ๐ Best Practices
Use Namespaces
for Isolation
- Organize resources by namespaces for better management and access control.
Label Resources
- Use labels to organize and select resources efficiently.
Monitor and Log
- Continuously monitor your cluster and collect logs for troubleshooting and performance analysis.
Automate with Scripts
- Use scripts to automate repetitive tasks and ensure consistency.
Secure Your Cluster
- Implement RBAC, network policies, and secure access controls to protect your cluster.
๐ Conclusion
Mastering Kubernetes commands, from beginner to advanced levels, is essential for DevOps engineers to manage and troubleshoot clusters effectively. This comprehensive guide serves as a valuable reference for navigating your Kubernetes environment. By following best practices and leveraging these commands, you can ensure a robust and efficient Kubernetes setup.
Happy Clustering!๐
Thank you for reading my blog โฆ:)
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