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| title | content_type | weight |
|---|---|---|
| Configure Pod Initialization | task | 130 |
This page shows how to use an Init Container to initialize a Pod before an application Container runs.
{{% heading "prerequisites" %}}
{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
Create 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:
{{< codenew file="pods/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.
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://info.cern.ch
Notice that the init container writes the index.html file in the root directory
of the nginx server.
Create the Pod:
kubectl apply -f https://k8s.io/examples/pods/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
init-demo 1/1 Running 0 1m
Get a shell into the nginx 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:
<html><head></head><body><header>
<title>http://info.cern.ch</title>
</header>
<h1>http://info.cern.ch - home of the first website</h1>
...
<li><a href="http://info.cern.ch/hypertext/WWW/TheProject.html">Browse the first website</a></li>
...
{{% heading "whatsnext" %}}
- Learn more about communicating between Containers running in the same Pod.
- Learn more about Init Containers.
- Learn more about Volumes.
- Learn more about Debugging Init Containers