How to merge two configmaps using volume mount in kubernetes

Question

I am having two different config maps test-configmap and common-config. I tried to mount them at the same location, but one config map over

Answer 1

You cannot mount two ConfigMaps to the same location.

But mentioning subPath and key for every item in each configmaps will let you get items from both configmaps in the same location. You'll have to write mount points for each file manually:

apiVersion: v1
kind: Pod
metadata:
  name: config-single-file-volume-pod
spec:
  containers:
    - name: test-container
      image: gcr.io/google_containers/busybox
      command: [ "/bin/sh", "-c", "cat /etc/special-key" ]
      volumeMounts:
      - name: config-volume-1
        mountPath: /etc/special-key1
        subPath: path/to/special-key1
      - name: config-volume-2
        mountPath: /etc/special-key2
        subPath: path/to/special-key2
  volumes:
    - name: config-volume-1
      configMap:
        name: test-configmap1
        items:
        - key: data-1
          path: path/to/special-key1
    - name: config-volume-2
      configMap:
        name: test-configmap2
        items:
        - key: data-2
          path: path/to/special-key2
restartPolicy: Never

Another way is to mount them under same directory, but different subPath so that you don't have to specify items by hand. But, here keys from each configmap will be put into two different directories:

apiVersion: v1
kind: Pod
metadata:
  name: config-single-file-volume-pod
spec:
  containers:
    - name: test-container
      image: gcr.io/google_containers/busybox
      command: [ "/bin/sh", "-c", "cat /etc/special-key" ]
      volumeMounts:
      - name: config-volume-1
        mountPath: /etc/special-keys
        subPath: cm1
      - name: config-volume-2
        mountPath: /etc/special-keys
        subPath: cm2
  volumes:
    - name: config-volume-1
      configMap:
        name: test-configmap1
    - name: config-volume-2
      configMap:
        name: test-configmap2
restartPolicy: Never

cm1 and cm2 will be two directories containing files derived from keys in test-configmap1 and test-configmap2 respectively.