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| title |
|---|
| Configuring Pod Initialization |
{% capture overview %} This page shows how to use an init Container to initialize a Pod before the application Container runs.
{% endcapture %}
{% capture prerequisites %}
{% include task-tutorial-prereqs.md %}
{% endcapture %}
{% capture steps %}
Creating a Pod that has an init Container
In this exercise you create a Pod that has one application Container and one init Container. The init Container runs to completion before the application container starts.
Here is the configuration file for the Pod:
{% include code.html language="yaml" file="init-containers.yaml" ghlink="/docs/tasks/configure-pod-container/init-containers.yaml" %}
In the configuration file, you can see that the Pod has a Volume that the init Container and the application Container share. Notice that the init Container is a beta feature and is specified as an annotation.
The init Container mounts the
shared Volume at /work-dir, and the application Container mounts the shared
Volume at /usr/share/nginx/html. The init Container runs the following command
and then terminates:
wget -O /work-dir/index.html http://kubernetes.io
Notice that the init Container writes the index.html file in the root directory
of the nginx server.
Create the Pod:
kubectl create -f http://k8s.io/docs/tasks/configure-pod-container/init-containers.yaml
Verify that the nginx Container is running:
kubectl get pod init-demo
The output shows that the nginx Container is running:
NAME READY STATUS RESTARTS AGE
nginx 1/1 Running 0 43m
Get a shell into nginx the Container running in the init-demo Pod:
kubectl exec -it init-demo -- /bin/bash
In your shell, send a GET request to the nginx server:
root@nginx:~# apt-get update
root@nginx:~# apt-get install curl
root@nginx:~# curl localhost
The output shows that nginx is serving the web page that was written by the init container:
<!Doctype html>
<html id="home">
<head>
...
"url": "http://kubernetes.io/"}</script>
</head>
<body>
...
<p>Kubernetes is open source giving you the freedom to take advantage ...</p>
...
{% endcapture %}
{% capture whatsnext %}
- Learn more about communicating between Containers running in the same Pod.
- Learn more about init Containers.
- Learn more about Volumes.
{% endcapture %}
{% include templates/task.md %}