92 lines
2.5 KiB
Markdown
92 lines
2.5 KiB
Markdown
---
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title: Configuring Pod Initialization
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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 the
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application Container runs.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture steps %}
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## Creating 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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{% include code.html language="yaml" file="init-containers.yaml" ghlink="/docs/tasks/configure-pod-container/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. Notice that the init Container
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is a beta feature and is specified as an annotation.
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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 http://k8s.io/docs/tasks/configure-pod-container/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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nginx 1/1 Running 0 43m
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Get a shell into nginx the 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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{% endcapture %}
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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/configure-pod-container/communicate-containers-same-pod/).
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* Learn more about [init Containers](/docs/user-guide/pods/init-container/).
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* Learn more about [Volumes](/docs/user-guide/volumes/).
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{% endcapture %}
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{% include templates/task.md %}
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