website/docs/tasks/configure-pod-container/attach-handler-lifecycle-event.md

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Attaching Handlers to Container Lifecycle Events

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This page shows how to attach handlers to Container lifecycle events. Kubernetes supports the postStart event and the preStop event. Kubernetes sends the postStart event immediately after a Container is started, and it sends the preStop event immediately before the Container is terminated.

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Defining postStart and preStop handlers

In 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:

{% include code.html language="yaml" file="lifecycle-events.yaml" ghlink="/docs/tasks/configure-pod-container/lifecycle-events.yaml" %}

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 create -f http://k8s.io/docs/tasks/configure-pod-container/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

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• Learn more about Container lifecycle hooks
• Learn more about the lifecycle of a Pod.

Reference

• Lifecycle
• Container

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