my-docs/Containerization & Orchestration/Kubernetes/3-Commands.md

Kubernetes Command Reference

This document provides a reference for common kubectl commands used for managing Kubernetes clusters. Use the examples and explanations below to help manage nodes, namespaces, pods, deployments, and more.

Table of Contents

• Kubernetes Command Reference
  • Table of Contents
  • General Commands
  • Node Management
  • Namespace Management
  • Pod Management
    • Listing Pods
    • Running a Pod
    • Deleting a Pod
  • API Resources and Documentation
  • Logs and Pod Information
  • Applying YAML Files
  • Managing Nodes and Labels
  • Viewing Cluster Resources
  • ReplicaSet and Deployment Management
  • Additional Information

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General Commands

• List API Resources

  kubectl api-resources
  

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Node Management

• Show all nodes

  kubectl get node
  

• Set a label on a node

  kubectl label nodes <node-name> kubernetes.io/<label-key>=<label-value>
  

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Namespace Management

• List all namespaces

  kubectl get namespaces
  # or the abbreviated version:
  kubectl get ns
  

• Create a custom namespace

  kubectl create ns <namespace-name>
  

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Pod Management

Listing Pods

• List pods in the default namespace

  kubectl get pod
  

• List pods with detailed information (wide output) in the default namespace

  kubectl get pod -o wide
  

• List pods with detailed information in a specific namespace

  kubectl get pod -o wide -n <namespace-name>
  

Running a Pod

• Run a new pod

  Use the following command structure to run a pod with various options:

  kubectl run <pod-name> <switch> {
    --image=<image-name>,                # Container image to use
    --port=<port-number>,                # Port that the container exposes
    -n <namespace-name>,                 # Namespace in which to run the pod
    --env="KEY=VALUE",                   # Environment variables for the container
    --command,                           # Treat the following arguments as the command
    --replicas=<number>,                 # Number of pod replicas to create
    --labels="key=value,key2=value2",    # Labels to assign to the pod(s)
    --dry-run=client,                    # Print the object without creating it
    --restart=<Always|OnFailure|Never>,  # Pod restart policy
    --overrides='<json>',                # JSON override for the generated object
    --image-pull-policy=<policy>,        # Image pull policy (Always, IfNotPresent, Never)
    --limits=cpu=<cpu>,memory=<memory>,   # Resource limits for the container
    --requests=cpu=<cpu>,memory=<memory>  # Resource requests for the container
  }
  

  • Example:

    kubectl run mypod --image=nginx --port=80 -n mynamespace \
      --env="ENV_VAR_NAME=VALUE" --command -- nginx -g "daemon off;" \
      --replicas=3 --labels="app=myapp,env=prod" --dry-run=client \
      --restart=Always --overrides='{"spec": {"containers": [{"name": "nginx", "image": "nginx"}]}}' \
      --image-pull-policy=IfNotPresent --limits=cpu=100m,memory=256Mi \
      --requests=cpu=50m,memory=128Mi
    

Deleting a Pod

• Delete a pod in a custom namespace

  kubectl delete pod -n <namespace-name> <pod-name>
  

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API Resources and Documentation

• Get documentation for an API resource

  kubectl explain <api-resource-name>
  

  • Example:

    kubectl explain pod
    

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Logs and Pod Information

• Stream logs for a running pod

  kubectl logs -f -n <namespace-name> <pod-name>
  

• Get detailed state and log information for a pod

  kubectl describe pod -n <namespace-name> <pod-name>
  

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Applying YAML Files

• Apply configuration from a YAML file to a specific namespace

  kubectl apply -f <yaml-file> -n <namespace-name>
  

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Managing Nodes and Labels

• Label a node with a custom key-value pair

  kubectl label nodes <node-name> kubernetes.io/<label-key>=<label-value>
  

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Viewing Cluster Resources

• Display all resources loaded in a namespace

  kubectl get all -n <namespace-name>
  

• Display replica sets, pods, and deployments in a specific namespace

  kubectl get rs,pod,deployment -n <namespace-name>
  

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ReplicaSet and Deployment Management

• Scale a ReplicaSet

  kubectl scale rs <replicaset-name> -n <namespace-name> --replicas=<count>
  

• View rollout history of a deployment

  kubectl rollout history deployment -n <namespace-name> <deployment-name>
  

• View details of a specific revision in a deployment's rollout history

  kubectl rollout history deployment -n <namespace-name> <deployment-name> --revision <number>
  

• Roll back a deployment to a specific revision

  kubectl rollout undo deployment -n <namespace-name> <deployment-name> --to-revision=<number>
  

  Note: The command for rolling back to a specific revision is kubectl rollout undo rather than using --to-revision with kubectl rollout history.

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Additional Information

• Static Manifest Files

  All YAML files located under /etc/kubernetes/manifests/ are automatically loaded after a server reboot.

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