100-Days-Of-DevOps-Challenge-KodeKloud

Execute Rolling Updates in Kubernetes

An application currently running on the Kubernetes cluster employs the nginx web server. The Nautilus application development team has introduced some recent changes that need deployment. They’ve crafted an image nginx:1.18 with the latest updates.

Execute a rolling update for this application, integrating the nginx:1.18 image. The deployment is named nginx-deployment.
Ensure all pods are operational post-update.

Note: The kubectl utility on jump_host is set up to operate with the Kubernetes cluster

Steps

Let’s get the deployments, and pods

 kubectl get deployments.apps
 NAME               READY   UP-TO-DATE   AVAILABLE   AGE
 nginx-deployment   3/3     3            3           4m33s

 kubectl get pods
 NAME                               READY   STATUS    RESTARTS   AGE
 nginx-deployment-989f57c54-mnznk   1/1     Running   0          4m52s
 nginx-deployment-989f57c54-sqf5h   1/1     Running   0          4m52s
 nginx-deployment-989f57c54-vgjd8   1/1     Running   0          4m52s

Let’s find details of the deployments for any pod

 kubectl describe pods nginx-deployment-989f57c54-mnznk

 Name:             nginx-deployment-989f57c54-mnznk
 Namespace:        default
 Priority:         0
 Service Account:  default
 Node:             kodekloud-control-plane/172.17.0.2
 Start Time:       Mon, 15 Sep 2025 10:38:31 +0000
 Labels:           app=nginx-app
                 pod-template-hash=989f57c54
 Annotations:      <none>
 Status:           Running
 IP:               10.244.0.6
 IPs:
 IP:           10.244.0.6
 Controlled By:  ReplicaSet/nginx-deployment-989f57c54
 Containers:
 nginx-container:
     Container ID:   containerd://5928ff11805390e2ac2b10bbaee9a5dcb540d6c534d162ca49c975c270280d11
     Image:          nginx:1.16
     Image ID:       docker.io/library/nginx@sha256:d20aa6d1cae56fd17cd458f4807e0de462caf2336f0b70b5eeb69fcaaf30dd9c
     Port:           <none>
     Host Port:      <none>
     State:          Running
     Started:      Mon, 15 Sep 2025 10:38:38 +0000
     Ready:          True
     Restart Count:  0
     Environment:    <none>
     Mounts:
     /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-v2jf9 (ro)
 Conditions:
 Type              Status
 Initialized       True 
 Ready             True 
 ContainersReady   True 
 PodScheduled      True 
 Volumes:
 kube-api-access-v2jf9:
     Type:                    Projected (a volume that contains injected data from multiple sources)
     TokenExpirationSeconds:  3607
     ConfigMapName:           kube-root-ca.crt
     ConfigMapOptional:       <nil>
     DownwardAPI:             true
 QoS Class:                   BestEffort
 Node-Selectors:              <none>
 Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
 Events:
 Type    Reason     Age    From               Message
 ----    ------     ----   ----               -------
 Normal  Scheduled  10m    default-scheduler  Successfully assigned default/nginx-deployment-989f57c54-mnznk to kodekloud-control-plane
 Normal  Pulling    10m    kubelet            Pulling image "nginx:1.16"
 Normal  Pulled     9m57s  kubelet            Successfully pulled image "nginx:1.16" in 5.385304195s (5.385392439s including waiting)
 Normal  Created    9m57s  kubelet            Created container nginx-container
 Normal  Started    9m57s  kubelet            Started container nginx-container

We can see the current image version: 1.16

Let’s update image version:
```
 kubectl set image deployments/nginx-deployment nginx-container=nginx:1.18
```
We have to use set image command with deployment name and container name

Let’s verify the rollout status

 kubectl rollout status deployments/nginx-deployment

Good to Know?

Rolling Updates

Zero Downtime: Update applications without service interruption
Gradual Replacement: Replace pods incrementally
Health Checks: Ensure new pods are ready before proceeding
Automatic Rollback: Rollback on failure detection

Update Strategies

RollingUpdate: Default strategy, gradual replacement
Recreate: Terminate all pods before creating new ones
MaxUnavailable: Maximum pods that can be unavailable
MaxSurge: Maximum pods that can be created above desired

Rollout Commands

Set Image: kubectl set image deployment/name container=image:tag
Status: kubectl rollout status deployment/name
History: kubectl rollout history deployment/name
Undo: kubectl rollout undo deployment/name

Best Practices

Health Probes: Configure readiness and liveness probes
Resource Limits: Ensure adequate resources for updates
Testing: Test updates in staging environment
Monitoring: Monitor application during rollout

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