cppxaxa/kubernetes-config-map-as-file

Mount a config map value as a text file inside a pod

kubernetes-config-map-as-file inside a pod

• In this experiment, we're going to request kubernetes to mount a volume with some files.
• The files will have the content of the config map

Items

• configmap-app002.yaml
• app002-pod.yaml

configmap-app002.yaml

It contains non-sensitive information, that a microservice may need for initialization or proper working. It may hold the information about where the microservice is deployed.

app002-pod.yaml

• It contains a containerized application
• It has a ssh server
• As a proof, we can use kubernetes port-forwarding, connect via ssh, and explore the directories of the pod
• We'll observe the files

Steps

Prepare the container, test locally

1. Use the command, to start a local docker container with ssh.

docker run --rm -itp 2222:2222 --name=ssh --hostname=ssh -e SUDO_ACCESS=true -e PASSWORD_ACCESS=true -e USER_PASSWORD=dummy -e USER_NAME=dummy linuxserver/openssh-server sh

2. Now in the localhost machine, try connecting the docker container instance using any SSH client
3. Tested successfully with "moba" SSH client

Create a pod in kubernetes cluster, test with kubernetes port-forwarding

1. Use the yaml "configmap-app002.yaml" inside the "Deploy" folder to create a configmap object inside kubernetes cluster

kubectl create -f configmap-app002.yaml

2. Check and confirm the presence of config map in kubernetes cluster

kubectl get configmaps kubectl describe configmaps/configmap-app002

3. Create the pod with the docker container using the "app002-pod.yaml" yaml file and confirm its presence

kubectl create -f app002-pod.yaml kubectl get pods

4. Start the kubernetes port-forwarding

kubectl port-forward pods/mypod 2222:2222

5. Connect the pod with openssh-server endpoint at localhost:2222 using any SSH client with the credentials dummy:dummy
6. Explore the files inside the directory /etc/foo

cd /etc/foo ls cat game.properties cat player_initial_lives cat user-interface.properties

References

• https://kubernetes.io/docs/concepts/configuration/configmap/
• https://github.com/linuxserver/docker-openssh-server