This demonstrates how to run a basic initializer with python kubernetes library the sample code allows to injects a given image in all your deployments (or filter with a specific annotation)

a cluster with --admission-control:

minikube start --extra-config=apiserver.Admission.PluginNames="Initializers,NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota"

you can use the two following optional environment variables:

• INJECT_POD pointing to the image to inject in the deployment containers list
• ANNOTATION the name of an annotation to restricts pod injection only to deployments having the corresponding annotation set to "true"

You can then either manually launch the controller

python initializer.py

Or run it as a deployment ( note that we prevent the controller to be affected by any existing initializer )

kubectl create -f initializer.yml

On openshift

oc new-project initializer
oc adm policy add-cluster-role-to-user cluster-admin -z default -n initializer
oc new-app karmab/sampleinitializer

this snippet with create an initialization configuration matching deployments

kubectl create -f initialization_deployments.yml

test with with a sample deployment

kubectl run nginx --image=nginx
kubectl describe deployment nginx

• use go instead of python
• autocreate the initializer configuration when starting the controller
• store this conf in a configmap and read it when starting