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How to Restart Kubernetes Pods With Kubectl

Did you know pods don’t always terminate when an application fails in Kubernetes? Although there are no direct `kubectl restart pod` command, there are multiple ways to restart pods using `kubectl`.

Today, we will examine pod statuses, why restarts are necessary, and five effective methods for restarting pods.

Different Pod Statuses in Kubernetes

A pod in Kubernetes can be in one of five states:

• Pending: At least one container has not yet been created.
• Running: All containers are created, and the pod is bound to a Node. Containers are running or in the process of starting or restarting.
• Succeeded: All containers have terminated successfully and will not restart.
• Failed: All containers have terminated, with at least one container failing (non-zero exit code).
• Unknown: The pod status cannot be determined.

If a pod gets stuck in an error state, like CrashLoopBackOff, it means Kubernetes is repeatedly trying to restart the pod but failing. When this happens, we must carry out a manual pod restart.

How to Restart Pods in Kubernetes

Our Experts have put together five methods to restart pods using `kubectl`. Remember that restarting pods will create new pods with different names.

Method 1: Rollout Restart

A rollout restart is the safest and most efficient way to restart pods, as it gradually replaces pods without causing downtime (available from Kubernetes v1.15).

kubectl rollout restart deployment <deployment_name> -n <namespace>
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This command terminates pods and recreates them one by one. This method works well in production environments where uptime is critical.

Method 2: Scale Down and Up (Risk of Downtime)

If downtime is acceptable, scaling pods to zero and backup is a simple option.

We can scale down to zero replicas (delete all pods) with this command:

kubectl scale deployment deployment_name -n namespace –replicas=0Copy Code

To scale back up to the desired number of replicas with this command:

kubectl scale deployment deployment_name -n namespace –replicas=3Copy Code

To check pod status during scaling, run:

kubectl get pods -n namespaceCopy Code

In this method, all pods are terminated simultaneously, causing downtime. It works well in development or testing environments.

Method 3: Delete Pod or ReplicaSet

Deleting a pod will trigger Kubernetes to recreate it automatically.

To delete a single pod, run:

kubectl delete pod pod_name -n namespaceCopy Code

Or, to delete multiple pods by label, run:

kubectl delete pod -l "app=myapp" -n namespaceCopy Code

If there are lots of pods, we can delete the ReplicaSet:

kubectl delete replicaset replicaset_name -n namespaceCopy Code

Method 4: Force Replace Pods

We can force Kubernetes to restart pods by fetching their YAML and using `kubectl replace`.

kubectl get pod pod_name -n  -o yaml | kubectl replace --force -f -Copy Code

Here, the pod is deleted and recreated with the same configuration. This method works well if we can’t access the original YAML file.

Method 5: Restart via Environment Variable Update

Modifying a pod’s environment variable triggers a restart. A simple trick is to update a timestamp.

kubectl set env deployment deployment_name -n namespace DEPLOY_DATE="$(date)"
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Here, Kubernetes restarts pods to apply the new environment variable.

It works well in CI/CD pipelines where we want to trigger restarts without changing pod configuration.

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Conclusion

While Kubernetes doesn’t have a direct `kubectl restart pod` command, the above methods let us restart pods depending on our needs.

In brief, our Support Experts demonstrated how to restart Kubernetes Pods With Kubectl.