Learning Kubernetes

Comprehensive Guide to Kubernetes Deployment

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Jay Kasundra
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Kubernetes Deployment Controller Object

  • Create Replicas of Pod and deploy the Pod instances to the Worker Nodes

  • Here, the Replicas are created using ReplicaSet

  • Used to Deploy the Replicas of Pods in the available WorkerNodes

  • Perform Scale-Up and Scale-Down the Pod Instances

  • Perform Upgrade and Downgrade the Pod Versions without any downtime.

  • Deployment Strategy called - Rolling Update Strategy to ensure Zero DownTime during Upgrade/Downgrade.

  • Creates :

      1. Deployment Controller

        1. Replicaset

        2. Pod Instances

Replicaset Controller Object

  • Used to Create Replicas/Copies of pods

  • Replicaset Created Automatically during the Deployment Object Creation

Let's see how deployment works.

  1. Deployment YAML file

    1.  # nginx-deploy.yaml
 apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: nginx-deploy
   labels:
     app: nginx-deploy-lbl
 spec:
   replicas: 3
   template:
     metadata:
       labels:
         app: nginx-app
     spec:
       containers:
       - name: nginx-container
         image: nginx:stable-otel
         ports:
         - containerPort: 80
   selector:
     matchLabels:
       app: nginx-app

  2. Create and Display Deployment

    1.  kubectl create -f nginx-deploy.yaml 
 kubectl get deploy -l app=nginx-app
 kubectl get rs -l app=nginx-app
 kubectl get po -l app=nginx-app
 kubectl describe deploy nginx-deploy

  3. Testing: Rollback update

    1.  kubectl set image deploy nginx-deploy nginx-container=nginx:stable-pearl
 kubectl rollout status deployment/nginx-deploy
 kubectl rollout undo deployment/nginx-deploy
 kubectl rollout status deployment/nginx-deploy
 kubectl describe deploy nginx-deploy | grep -i image

    2. When wrong image version mentioned, then “ImagePullBackOff” Error is shown

  4. Testing: Update Version of "nginx:stable-otel" to "nginx:stable-perl"

    1.  kubectl set image deploy nginx-deploy nginx-container=nginx:stable-perl
 # or
 kubectl edit deploy nginx-deploy

 kubectl rollout status deployment/nginx-deploy
 kubectl get deploy

  5. Testing: Scale UP

    1.  kubectl scale deployment nginx-deploy --replicas=5
 kubectl get deploy
 kubectl get po -o wide

  6. Testing: Scale DOWN

    1.  kubectl scale deployment nginx-deploy --replicas=3
 kubectl get deploy
 kubectl get po -o wide

  7. Cleanup

    1.  kubectl delete -f nginx-deploy.yaml
 kubectl get deploy
 kubectl get rs
 kubectl get po

Kubernetes services :

NodePort Service

  • Used to Expose the pod to Internet

  • It is a special type of service, which can assign addition port ranges from 30000 to 32767.

  • Map the deployment object to NodePort Service, it will be applicable to all corresponding pods.

  • Access it thru.

    • Open Web-browser and access webapage using

      •   http://<external-nodeip>:<nodeport>
Kubernetesdeployment