my-docs/kubernetes/commands.md

Kubernetes

kubectl Command Reference

Get State of API Resources

kubectl api-resources

Node Management

• Show all nodes:

  kubectl get node
  

Namespace Management

• List all namespaces:

  kubectl get namespaces
  

  kubectl get ns
  

• Create a custom namespace:

  kubectl create ns <namespace-name>
  

Pod Management

• Get the list of pods in the default namespace:

  kubectl get pod
  

• Get the list of pods in the default namespace with full information:

  kubectl get pod -o wide
  

• Get the list of pods in a custom namespace with full information:

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

Running a Pod

• Run a new pod:

    kubectl run <pod-name> <switch> {
    --image=<image-name>,                # Specifies the container image to use
    --port=<portnumber>,                 # Specifies the port that the container exposes
    -n <namespace-name>,                 # Specifies the namespace
    --env="KEY=VALUE",                   # Sets environment variables in the container
    --command,                           # Treats the rest of the arguments as the command to run in the container
    --replicas=<number>,                 # Specifies the number of replicas for the deployment
    --labels="key=value,key2=value2",    # Adds labels to the pod(s)
    --dry-run=client,                    # Prints the object that would be sent, without creating it
    --restart=<Always|OnFailure|Never>,  # Determines the restart policy for the pod
    --overrides='<json>',                # Provides a JSON override for the generated object
    --image-pull-policy=<policy>,        # Specifies the image pull policy (Always, IfNotPresent, Never)
    --limits=cpu=<cpu>,memory=<memory>,  # Specifies resource limits for the container
    --requests=cpu=<cpu>,memory=<memory> # Specifies 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>
  

API Resource Documentation

• Get documentation of an API resource:

  kubectl explain <api-resource-name>
  

  • Example:

    kubectl explain pod
    

Logging and Pod Information

• Get and follow logs of a pod (pod must be created and running):

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

• Get logs and state information of a pod (works at any time):

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

Apply Yaml File

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

View Pod Details

kubectl get pod -n my-ns <pod-name> -o yaml

This command retrieves and displays the YAML configuration of the pod testpod1 in the namespace my-ns.

Label a Node

kubectl label node <node-name> kubernetes.io/<var-name>=<var-value>
kubectl get nodes --show-labels

Retrieve the ReplicaSet

To retrieve information about the ReplicaSet in the my-ns namespace, use the following command:

kubectl get rs -n my-ns

Delete All Pods in the Namespace

To delete all pods in the my-ns namespace, use the following command:

kubectl delete pod --all -n my-ns

Change the Replica Count to 5

To scale the ReplicaSet to 5 replicas, you can use one of the following methods:

1. Using the kubectl scale Command

kubectl scale rs my-app --replicas=5 -n my-ns

Commands to Manage the Deployment

Scale the Deployment

To scale the Deployment to 6 replicas:

kubectl -n my-ns scale deployment myapp --replicas 6

Retrieve Deployment, ReplicaSets, and Pods

To retrieve information about the Deployment, ReplicaSets, and Pods:

kubectl get deployment,rs,po myapp -n my-ns

Delete the Deployment

To delete the Deployment:

kubectl delete deployment myapp -n my-ns

Retrieve ReplicaSets

To retrieve ReplicaSets:

kubectl get rs -n my-ns

Rollback a Deployment

To undo the last rollout:

kubectl rollout undo deployment -n my-ns myapp

To view rollout history:

kubectl rollout history deployment -n my-ns 

To view a specific revision:

kubectl rollout history deployment -n my-ns --revision 2

To rollback to a specific revision:

kubectl rollout undo deployment -n my-ns myapp --to-revision 2

Annotate Deployment with Change Cause

To add a change cause annotation:

kubectl annotate deployment/myapp -n my-ns myapp "kubectl.kubernetes.io/change-cause=v14 released"

Horizontal Pod Autoscaler

To create an autoscaler for the Deployment:

kubectl -n my-ns autoscale deployment nginx --cpu-percent=50 --min=4 --max=10