Kubernetes-ConfigMaps

A ConfigMap is an API object used to store non-confidential data in key-value pairs. Pods can consume ConfigMaps as environment variables, command-line arguments, or as configuration files in a volume.

A ConfigMap allows you to decouple environment-specific configuration from your container images, so that your applications are easily portable.

LAB

1. Creating Configmap from "multiple files" & Consuming it inside Pod from "volumes" 

1a.  Create Configmap "nginx-configmap-vol" from "multiple files":

------------------------------------------------------------------

echo -n 'Properties for Staging env' > web_stag.xml

echo -n 'Properties for Prod env' > web_prod.xml

kubectl create configmap nginx-configmap-vol --from-file=web_stag.xml --from-file=web_prod.xml

# rm *

• kubectl get configmaps
• kubectl get configmaps nginx-configmap-vol -o yaml
• kubectl describe configmaps nginx-configmap-vol

1b.  Consume above "nginx-configmap-vol" configmap inside Pod from "volumes" 

#nginx-pod-configmap-vol.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx-pod-configmap-vol

spec:

  containers:

  - name: nginx-container

    image: nginx

    volumeMounts:

    - name: test-vol

      mountPath: "/etc/non-sensitive-data"

      readOnly: true

  volumes:

    - name: test-vol

      configMap:

        name: nginx-configmap-vol

        items:

        - key: web_stag.xml

          path: web.xml

==========================================================

1c. Create | Display | Validate:

--------------------------------

Create

kubectl create -f nginx-pod-configmap-vol.yaml

Display

kubectl get po

kubectl get configmaps

kubectl describe pod nginx-pod-configmap-vol

 Validate from "inside" the pod

kubectl exec nginx-pod-configmap-vol -it -- bash

cd /etc/non-sensitive-data

ls 

cat web.xml

exit

(OR)

# Validate from "outside" the pod

kubectl exec nginx-pod-configmap-vol ls /etc/non-sensitive-data

kubectl exec nginx-pod-configmap-vol cat /etc/non-sensitive-data/web.xml

*************************************************************************************************************************************************

2. Creating Configmap from "literal values" & Consuming it inside Pod from "environment variables"  

2a.  Create configmap “redis-configmap-env” from "literal values"

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kubectl create configmap redis-configmap-env --from-literal=stagenv=stagenvvalue --from-literal=prodenv=prodenvvalue

kubectl get configmap

kubectl describe configmap redis-configmap-env

===============================================================================

2b. Consume “redis-configmap-env” configmap inside pod from “Environment Variables” inside pod

# redis-pod-configmap-env.yaml

apiVersion: v1

kind: Pod

metadata:

  name: redis-pod-configmap-env

spec:

  containers:

  - name: redis-container

    image: redis

    env:

      - name: PROD

        valueFrom:

          configMapKeyRef:

            name: redis-configmap-env

            key: prodenv

      - name: STAG

        valueFrom:

          configMapKeyRef:

            name: redis-configmap-env

            key: stagenv

  restartPolicy: Never

2c. Create | Display | Validate:

# Create

kubectl create -f  redis-pod-configmap-env.yaml

# Display

kubectl get pods

kubectl get configmaps

kubectl describe pod redis-pod-configmap-env

# Validate from "inside" the pod

kubectl exec -it redis-pod-configmap-env -- env

(OR)

# Validate from "outside" the pod

kubectl exec redis-pod-configmap-env -- env

Try Your Self

kubectl create -f podcm.yaml

#cm.yaml

apiVersion: v1

kind: ConfigMap

metadata:

  name: game-demo

data:

  # property-like keys; each key maps to a simple value

  player_initial_lives: "3"

  ui_properties_file_name: "user-interface.properties"

  #

  # file-like keys

  game.properties: |

    enemy.types=aliens,monsters

    player.maximum-lives=5

  user-interface.properties: |

    color.good=purple

    color.bad=yellow

    allow.textmode=true

kubectl create -f cm.yaml

kubectl get cm

# To consume the Config map create below pod

#podcm.yaml

apiVersion: v1

kind: Pod

metadata:

  name: configmap-demo-pod

spec:

  containers:

    - name: demo

      image: nginx

      env:

        # Define the environment variable

        - name: PLAYER_INITIAL_LIVES # Notice that the case is different here

                                     # from the key name in the ConfigMap.

          valueFrom:

            configMapKeyRef:

              name: game-demo           # The ConfigMap this value comes from.

              key: player_initial_lives # The key to fetch.

        - name: UI_PROPERTIES_FILE_NAME

          valueFrom:

            configMapKeyRef:

              name: game-demo

              key: ui_properties_file_name

      volumeMounts:

      - name: config

        mountPath: "/config"

        readOnly: true

  volumes:

    # You set volumes at the Pod level, then mount them into containers inside that Pod

    - name: config

      configMap:

        # Provide the name of the ConfigMap you want to mount.

        name: game-demo

        # An array of keys from the ConfigMap to create as files

        items:

        - key: "game.properties"

          path: "game.properties"

        - key: "user-interface.properties"

          path: "user-interface.properties"

3. Cleanup

# Delete configmaps

kubectl delete configmaps nginx-configmap-vol redis-configmap-env

# Delete pods

kubectl delete pods nginx-pod-configmap-vol redis-pod-configmap-env

# Validate

kubectl get pods

kubectl get configmaps

References

https://kubernetes.io/docs/concepts/configuration/configmap/#:~:text=A%20ConfigMap%20is%20an%20API%20object%20that%20lets%20you%20store,a%20valid%20DNS%20subdomain%20name.

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