94 lines
2.5 KiB
Markdown
94 lines
2.5 KiB
Markdown
---
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title: Configure Pod Initialization
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content_template: templates/task
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weight: 130
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---
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{{% capture overview %}}
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This page shows how to use an Init Container to initialize a Pod before an
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application Container runs.
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{{% /capture %}}
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{{% capture prerequisites %}}
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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{{% /capture %}}
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{{% capture steps %}}
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## Create a Pod that has an Init Container
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In this exercise you create a Pod that has one application Container and one
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Init Container. The init container runs to completion before the application
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container starts.
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Here is the configuration file for the Pod:
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{{< codenew file="pods/init-containers.yaml" >}}
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In the configuration file, you can see that the Pod has a Volume that the init
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container and the application container share.
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The init container mounts the
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shared Volume at `/work-dir`, and the application container mounts the shared
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Volume at `/usr/share/nginx/html`. The init container runs the following command
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and then terminates:
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wget -O /work-dir/index.html http://kubernetes.io
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Notice that the init container writes the `index.html` file in the root directory
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of the nginx server.
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Create the Pod:
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kubectl create -f https://k8s.io/examples/pods/init-containers.yaml
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Verify that the nginx container is running:
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kubectl get pod init-demo
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The output shows that the nginx container is running:
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NAME READY STATUS RESTARTS AGE
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init-demo 1/1 Running 0 1m
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Get a shell into the nginx container running in the init-demo Pod:
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kubectl exec -it init-demo -- /bin/bash
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In your shell, send a GET request to the nginx server:
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root@nginx:~# apt-get update
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root@nginx:~# apt-get install curl
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root@nginx:~# curl localhost
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The output shows that nginx is serving the web page that was written by the init container:
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<!Doctype html>
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<html id="home">
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<head>
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...
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"url": "http://kubernetes.io/"}</script>
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</head>
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<body>
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...
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<p>Kubernetes is open source giving you the freedom to take advantage ...</p>
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...
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{{% /capture %}}
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{{% capture whatsnext %}}
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* Learn more about
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[communicating between Containers running in the same Pod](/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/).
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* Learn more about [Init Containers](/docs/concepts/workloads/pods/init-containers/).
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* Learn more about [Volumes](/docs/concepts/storage/volumes/).
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* Learn more about [Debugging Init Containers](/docs/tasks/debug-application-cluster/debug-init-containers/)
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{{% /capture %}}
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