This page shows how to use an Init Container to initialize a Pod before an application Container runs.
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:
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:
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
/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 https://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 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:
<!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> ...