Creating ConfigMaps

There are three common ways to create a ConfigMap: from literal values on the command line, from an existing file, and from a YAML manifest. Each has its place. Knowing all three is required for the CKA exam, where you may be asked to create a ConfigMap from a file or to write the manifest directly.

From literal values

The quickest way to create a ConfigMap is with --from-literal. Each flag adds one key-value pair:

kubectl create configmap app-env \
  --from-literal=LOG_LEVEL=debug \
  --from-literal=REGION=eu-west-1 \
  --from-literal=MAX_RETRIES=5

kubectl get configmap app-env -o yaml

The data section contains your three key-value pairs, each as a string. This approach is fast for small sets of values but becomes unwieldy for more than a handful of keys.

From a file

When your application reads configuration from a file (a properties file, a config.yaml, an Nginx template), you store the file contents as a ConfigMap value:

nano app.properties

log.level=info
db.max.connections=50
feature.dark-mode=true

kubectl create configmap app-file-config --from-file=app.properties

kubectl describe configmap app-file-config

The key is the filename (app.properties) and the value is the full file content. When you mount this ConfigMap as a volume, the container receives a file named app.properties containing those lines. You can also set a custom key name:

kubectl create configmap app-custom-key --from-file=config=app.properties

Now the key is config instead of app.properties. This is useful when the mounting path in the container should differ from the original filename.

From a YAML manifest

For production workloads, store ConfigMaps in YAML and commit them to version control. Generating a skeleton with --dry-run is faster than writing from scratch:

kubectl create configmap app-env \
  --from-literal=LOG_LEVEL=debug \
  --from-literal=REGION=eu-west-1 \
  --dry-run=client -o yaml > configmap.yaml

Open the file:

cat configmap.yaml

You see the standard Kubernetes object structure with kind: ConfigMap and a data section. Edit the file to add or remove keys, then apply:

kubectl apply -f configmap.yaml

For a file-based ConfigMap in YAML, use the multiline string syntax:

nano nginx-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
data:
  nginx.conf: |
    server {
      listen 80;
      location / {
        root /usr/share/nginx/html;
      }
    }
  log-level: info

The | character starts a literal block scalar in YAML: newlines are preserved exactly. This is how multi-line config file content is stored in a ConfigMap manifest.

kubectl apply -f nginx-configmap.yaml
kubectl describe configmap nginx-config

Both keys appear: nginx.conf contains the full server block, and log-level contains the string info.

kubectl delete configmap app-env app-file-config app-custom-key nginx-config

Literal values for simple key-value config, --from-file for existing config files, YAML manifests for version-controlled production config: these three creation methods cover every ConfigMap scenario you will encounter. The next lesson shows how to inject ConfigMap data into containers as environment variables.