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Injecting Configuration from a Single File

Injecting Configuration from a Single File

Learn to inject a configuration from a single file using the ConfigMap volume.

Creating a ConfigMap

In its purest (and probably the most common) form, a ConfigMap takes a single file. For example, we can create one from the prometheus-conf.yml file.

Shell
kubectl create cm my-config \
    --from-file=prometheus-conf.yml

We create a ConfigMap (cm) called my-config. The data of the map is the content of the prometheus-conf.yml file.

Looking into the description

Let’s describe it and see what we get.

Shell
kubectl describe cm my-config

The output is as follows:

Shell
Name:         my-config
Namespace:    default
Labels:       <none>
Annotations:  <none>
Data
====
prometheus-conf.yml:
----
global:
  scrape_interval:     15s
scrape_configs:
  - job_name: prometheus
    metrics_path: /prometheus/metrics
    static_configs:
      - targets:
        - localhost:9090
Events:  <none>

The important part is located below Data. We can see the key which, in this case, is the name of the file (prometheus-conf.yml). Further down, we can see the contents of the file. ...