Killercoda ConfigMap Access in Pods

I am planning to take the CKA exam in the near future. I work with Kubernetes daily at my job, but am mostly self taught, so it is probably realistic to say that I have some knowledge gaps. This blog is part of my preparation, where I go through all the scenarios on Killercoda.

ConfigMap Access in Pods

https://killercoda.com/killer-shell-cka/scenario/configmap-pod-access

Create ConfigMaps

Create two ConfigMaps:

1. Create a ConfigMap named trauerweide with content tree=trauerweide
   
2. Create the ConfigMap stored in existing file /root/cm.yaml

In the documentation for creating configMaps we see an example for creating one with a literal (see here):

# Create a new config map named my-config with key1=config1 and key2=config2
  kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2

With the --from-literal argument we execute the first task:

$  kubectl create configmap trauerweide --from-literal=tree=trauerweide
configmap/trauerweide created

$ k get cm trauerweide -oyaml
apiVersion: v1
data:
  tree: trauerweide
kind: ConfigMap
metadata:
  creationTimestamp: "2026-04-25T14:14:51Z"
  name: trauerweide
  namespace: default
  resourceVersion: "11074"
  uid: d6e07cf0-cfd4-4e45-85a9-d2972a1cb2ac

For the second task we already have a configMap manifest prepared for us. This we can just apply as is:

$ cat /root/cm.yaml 
apiVersion: v1
data:
  tree: birke
  level: "3"
  department: park
kind: ConfigMap
metadata:
  name: birke

$ k apply -f /root/cm.yaml 
configmap/birke created

Access ConfigMaps in Pod

1. Create a Pod named pod1 of image nginx:alpine
2. Make key tree of ConfigMap trauerweide available as environment variable TREE1
3. Mount all keys of ConfigMap birke as volume. The files should be available under /etc/birke/*
4. Test env+volume access in the running Pod

I rarely write manifests from scratch. Let’s try with the help of the documentations for pods (see here) and the explicit guide how to make configMaps available to pods (see here). After some trial and error I landed on the following manifest, which creates a pod with one container and an attached volume. The volume is referencing the birke configmap and is mounted into the container at the path /etc/birke. The container also receives the value of the key tree from the configmap trauerweide as the environment variable TREE1.

$ vim pod.yml
apiVersion: v1
kind: Pod
metadata:
  name: pod1
spec:
  containers:
  - name: nginx
    image: nginx:alpine
    env:
    - name: TREE1
      valueFrom:
        configMapKeyRef:
          name: trauerweide
          key: tree
    volumeMounts:
    - name: birke
      mountPath: /etc/birke
  volumes:
  - name: birke
    configMap: 
      name: birke

We can now apply this manifest:

$ k apply -f pod.yml 
pod/pod1 created

To check the configuration we exec into the the pod interactively using the -it parameter and run sh. Here we see the environment variable and the mounted configMap in the filesystem:

$ k exec -it pod1 -- sh
# env | grep TREE1
TREE1=trauerweide
# ls -al /etc/birke/
total 16
drwxrwxrwx    3 root     root          4096 Apr 25 14:27 .
drwxr-xr-x    1 root     root          4096 Apr 25 14:28 ..
drwxr-xr-x    2 root     root          4096 Apr 25 14:27 ..2026_04_25_14_27_59.2433766962
lrwxrwxrwx    1 root     root            32 Apr 25 14:27 ..data -> ..2026_04_25_14_27_59.2433766962
lrwxrwxrwx    1 root     root            17 Apr 25 14:27 department -> ..data/department
lrwxrwxrwx    1 root     root            12 Apr 25 14:27 level -> ..data/level
lrwxrwxrwx    1 root     root            11 Apr 25 14:27 tree -> ..data/tree