Kubectl Delete Pod: How to Delete/Drain Pods from a Kubernetes Node

In Kubernetes, a pod is the smallest deployable unit that can be created, managed, and scaled. Pods encapsulate one or more containers, storage resources, a unique network IP, and options that govern how the containers should run. Deleting pods is a common task that might be necessary for various reasons, such as rolling updates, scaling down applications, or removing malfunctioning pods.

This guide will provide an in-depth look at how to delete pods in Kubernetes using kubectl delete command.

Deleting Pods by Name

The most straightforward way to delete a pod is by its name. Use the following command to delete a specific pod:

 # kubectl delete pod pod-name

Example:

 # kubectl delete pod nginx-pod

This command will terminate the specified pod and remove it from the cluster.

pod "nginx-pod" deleted

Deleting Pods by Label

Labels are key/value pairs attached to objects in Kubernetes, such as pods, which can be used to select a group of objects. You can delete multiple pods at once by specifying a label selector.

 # kubectl delete pods -l label-key=label-value

Example:

 # kubectl delete pods -l app=nginx

This command deletes all pods with the label app=nginx.

pod "nginx-pod1" deleted
pod "nginx-pod2" deleted

Deleting Pods by Field Selector

Field selectors let you select Kubernetes resources based on the value of one or more resource fields. To delete pods by a field selector, use:

 # kubectl delete pods --field-selector field-selector

Example:

 # kubectl delete pods --field-selector status.phase=Failed

This command deletes all pods that are in the Failed phase.

pod "failed-pod1" deleted
pod "failed-pod2" deleted

Deleting Completed Pods

Pods that have completed their tasks and are in the Succeeded phase can also be deleted to free up resources.

 # kubectl delete pods --field-selector=status.phase=Succeeded

This command deletes all pods that are in the Succeeded phase.

pod "completed-pod1" deleted
pod "completed-pod2" deleted

Graceful Deletion of Pods

By default, Kubernetes gracefully shuts down pods. When a pod is deleted, it terminates, allowing it to complete ongoing operations.

To specify a grace period before forcefully terminating a pod, use the –grace-period flag:

 # kubectl delete pod pod-name --grace-period=seconds

Example:

 # kubectl delete pod nginx-pod --grace-period=30

This command gives the pod 30 seconds to shut down gracefully before being forcefully terminated.

Force Deleting Pods

In some cases, a pod might not terminate gracefully. To forcefully delete a pod, use the –force flag along with a grace period of 0:

 # kubectl delete pod pod-name --grace-period=0 --force

Example:

 # kubectl delete pod nginx-pod --grace-period=0 --force

This command immediately deletes the pod without waiting for graceful termination.

pod "nginx-pod" force deleted

Deleting Evicted Pods

Evicted pods are pods that have been forcibly removed from a node due to resource constraints or other reasons. These pods need to be manually deleted. You can identify evicted pods using a field selector and delete them:

 # kubectl delete pod --field-selector=status.reason=Evicted

Example:

 # kubectl delete pod --field-selector=status.reason=Evicted

Output.

pod "evicted-pod1" deleted
pod "evicted-pod2" deleted

Automating Pod Deletion with CronJobs

You can automate the deletion of pods using Kubernetes CronJobs. This is useful for recurring cleanup tasks.

1. Create a CronJob manifest file delete-pods-cronjob.yaml:

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: delete-failed-pods
spec:
  schedule: "0 */6 * * *" # Runs every 6 hours
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: kubectl
            image: bitnami/kubectl
            command:
            - /bin/sh
            - -c
            - kubectl delete pod --field-selector=status.phase=Failed
          restartPolicy: OnFailure

2. Apply the CronJob:

 # kubectl apply -f delete-pods-cronjob.yaml

This will create a CronJob that deletes failed pods every 6 hours.

cronjob.batch/delete-failed-pods created

Troubleshooting Pod Deletion

If you encounter issues while deleting pods, check the following:

• Pod Status: Ensure the pod is not already in the process of terminating.
• Pod Finalizers: Check if any finalizers prevent the pod from being deleted.
• Kubernetes Events: View events related to the pod to understand why they might not be deleted.

Commands to help with troubleshooting:

 # kubectl describe pod pod-name

Example:

 # kubectl describe pod nginx-pod

Output.

Name:         nginx-pod
Namespace:    default
Priority:     0
Node:         minikube/192.168.49.2
Start Time:   Tue, 08 Jul 2024 12:34:56 +0000
Labels:       none
Annotations:  none
Status:       Running
IP:           172.17.0.4
...

The kubectl get events command with the –field-selector option allows you to filter Kubernetes events related to a specific object, such as a pod. In this case, you want to filter events related to a nginx-pod pod.

 # kubectl get events --field-selector involvedObject.name=nginx-pod

This command will list all events associated with the nginx-pod.

LAST SEEN   TYPE      REASON              OBJECT            MESSAGE
20m         Normal    Scheduled           pod/nginx-pod     Successfully assigned default/nginx-pod to minikube
19m         Normal    Pulling             pod/nginx-pod     Pulling image "nginx"
18m         Normal    Pulled              pod/nginx-pod     Successfully pulled image "nginx" in 58.3154ms
18m         Normal    Created             pod/nginx-pod     Created container nginx
18m         Normal    Started             pod/nginx-pod     Started container nginx

Conclusion

Deleting pods in Kubernetes is a fundamental operation that is essential for maintaining and managing your cluster. Whether you need to delete a single pod or a group of pods, kubectl provides versatile commands. Understanding the different methods and options available for pod deletion ensures you can handle various scenarios effectively.

FAQs

1. How can I safely drain pods from a Kubernetes node?

Run kubectl drain node_name --ignore-daemonsets --delete-local-data to safely drain a node and evict its pods.

2. How do I cordon a Kubernetes node without draining pods?

You can mark a node unschedulable without evicting pods using kubectl cordon node_name command.

3. Can I drain a specific pod from a node instead of all pods?

No, kubectl drain evicts all pods from the node.

4. How do I force delete a stuck pod in Kubernetes?

You can forcefully delete a pod using kubectl delete pod pod_name --grace-period=0 --force command.

5. How do I undo a drain and allow new pods to be scheduled on a node?

You can uncordon a node to allow new pods to be scheduled by running: kubectl uncordon node_name

6. What’s the difference between kubectl delete pod and kubectl drain?

kubectl delete pod removes a specific pod, while kubectl drain evicts all pods from a node and marks the node as unschedulable.