kubernetes: How to create and use configmap from multiple files

Question

I have the documentation regarding the configmap:

https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/#define-container-environment-variables-using-configmap-data

From what I understand is I can create a config map(game-config-2) from two files (game.properties and ui.properties) using

kubectl create configmap game-config-2 --from-file=configure-pod-container/configmap/kubectl/game.properties --from-file=configure-pod-container/configmap/kubectl/ui.properties

Now I see the configmap

kubectl describe configmaps game-config-2
Name:           game-config-2
Namespace:      default
Labels:         <none>
Annotations:    <none>

Data
====
game.properties:        158 bytes
ui.properties:          83 bytes

How can I use that configmap? I tried this way:

    envFrom:
    - configMapRef:
        name: game-config-2

But this is not working, the env variable is not picking from the configmap. Or can I have two configMapRef under envFrom?

Answer 1

Yes, a pod or deployment can get env From a bunch of configMapRef entries:

    spec:
      containers:
      - name: encouragement-api
        image: registry-......../....../encouragement.api
        ports:
        - containerPort: 80
        envFrom:
          - configMapRef:
              name: general-config
          - configMapRef:
              name: private-config

Best to create them from yaml files for k8s law and order:

config_general.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: general-config
data:
  HOSTNAME: Develop_hostname
  COMPUTERNAME: Develop_compname
  ASPNETCORE_ENVIRONMENT: Development

encouragement-api/config_private.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: private-config
data:
  PRIVATE_STUFF: real_private

apply the two configmaps:

kubectl apply -f config_general.yaml
kubectl apply -f encouragement-api/config_private.yaml

Run and exec into the pod and run env |grep PRIVATE && env |grep HOSTNAME

I have config_general.yaml laying around in the same repo as the developers' code, they can change it however they like. Passwords and sensitive values are kept in the config_private.yaml file which is sitting elsewhere (a S3 encrypted bucket) and the values there are base64 encoded for an extra bit of security.

Answer 2

One solution to this problem is to create a ConfigMap with a multiple data key/values:

apiVersion: v1
kind: ConfigMap
metadata:
  name: conf
data:
  game.properties: |
    <paste file content here>
  ui.properties: |
    <paste file content here>

Just don't forget | symbol before pasting content of files.

Answer 3

Multiple --from-env-file are not allowed. Multiple --from-file will work for you.

Eg:

cat config1.txt 
    var1=val1

---

cat config2.txt 
    var3=val3
    var4=val4

---

kubectl create cm details2 --from-env-file=config1.txt --from-env-file=config2.txt -o yaml --dry-run

Output

apiVersion: v1
data:
  var3: val3
  var4: val4
kind: ConfigMap
  name: details2

---

k create cm details2 --from-file=config1.txt --from-file=config2.txt -o yaml --dry-run 

Output

apiVersion: v1
data:
  config1.txt: |
    var1=val1
  config2.txt: |
    var3=val3
    var4=val4
kind: ConfigMap
  name: details2