# Attach Handlers to Container Lifecycle Events

Attach Handlers to Container Lifecycle EventsThis page shows how to attach handlers to Container lifecycle events. Kubernetes supports the postStart and preStop events. Kubernetes sends the postStart event immediately after a Container is started, and it sends the preStop event immediately before the Container is terminated. A Container may specify one handler per event.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesTo check the version, enter kubectl version.Define postStart and preStop handlersIn this exercise, you create a Pod that has one Container. The Container has handlers for the postStart and preStop events.Here is the configuration file for the Pod:pods/lifecycle-events.yaml apiVersion: v1 kind: Pod metadata: name: lifecycle-demo spec: containers: - name: lifecycle-demo-container image: nginx lifecycle: postStart: exec: command: ["/bin/sh", "-c", "echo Hello from the postStart handler > /usr/share/message"] preStop: exec: command: ["/bin/sh","-c","nginx -s quit; while killall -0 nginx; do sleep 1; done"] In the configuration file, you can see that the postStart command writes a message file to the Container's /usr/share directory. The preStop command shuts down nginx gracefully. This is helpful if the Container is being terminated because of a failure.Create the Pod:kubectl apply -f https://k8s.io/examples/pods/lifecycle-events.yaml Verify that the Container in the Pod is running:kubectl get pod lifecycle-demo Get a shell into the Container running in your Pod:kubectl exec -it lifecycle-demo -- /bin/bash In your shell, verify that the postStart handler created the message file:root@lifecycle-demo:/# cat /usr/share/message The output shows the text written by the postStart handler:Hello from the postStart handler DiscussionKubernetes sends the postStart event immediately after the Container is created. There is no guarantee, however, that the postStart handler is called before the Container's entrypoint is called. The postStart handler runs asynchronously relative to the Container's code, but Kubernetes' management of the container blocks until the postStart handler completes. The Container's status is not set to RUNNING until the postStart handler completes.Kubernetes sends the preStop event immediately before the Container is terminated. Kubernetes' management of the Container blocks until the preStop handler completes, unless the Pod's grace period expires. For more details, see Pod Lifecycle.Note:Kubernetes only sends the preStop event when a Pod or a container in the Pod is terminated. This means that the preStop hook is not invoked when the Pod is completed. About this limitation, please see Container hooks for the detail.What's nextLearn more about Container lifecycle hooks.Learn more about the lifecycle of a Pod.ReferenceLifecycleContainerSee terminationGracePeriodSeconds in PodSpec