Mounting as a volume

Learn to mount a ConfigMap as a volume.

Mounting as a volume

When a ConfigMap is mounted as a volume, each key becomes a file in the mount directory. It's ideal for applications expecting a config file (nginx, Prometheus):

    spec:
      volumes:
        - name: ayar
          configMap:
            name: nginx-ayar
      containers:
        - name: nginx
          image: nginx:1.27
          volumeMounts:
            - name: ayar
              mountPath: /etc/nginx/conf.d
              readOnly: true

When a ConfigMap mounted as a volume is updated, the files refresh by themselves within a few minutes (unlike environment variables).

Mounting a single file

Mounting at a directory hides the existing files there. To place only a single file, subPath is used; however, a file mounted with subPath isn't refreshed when the ConfigMap is updated:

          volumeMounts:
            - name: ayar
              mountPath: /etc/nginx/nginx.conf
              subPath: nginx.conf

With items, only specific keys of the ConfigMap can be mounted, under the wanted file names.

Exercise Mount the config file

Write a pod's spec section (starting with spec:): an ayar volume from the nginx-ayar ConfigMap under volumes; container named nginx, image nginx:1.27; mount ayar at /etc/nginx/conf.d with readOnly: true.

Show example solution

spec:
  volumes:
    - name: ayar
      configMap:
        name: nginx-ayar
  containers:
    - name: nginx
      image: nginx:1.27
      volumeMounts:
        - name: ayar
          mountPath: /etc/nginx/conf.d
          readOnly: true

Test yourself

If the nginx-ayar ConfigMap has a default.conf key, which file appears in the container?
- /etc/nginx/conf.d/default.conf
- /etc/nginx/nginx-ayar
- /configmap/default.conf
- None
Show answer

/etc/nginx/conf.d/default.conf — The key becomes the file name, the value its content.

Mount to a single file, not a directory.

            - name: ayar
              mountPath: /etc/nginx/nginx.conf
              ____: nginx.conf

Show answer

            - name: ayar
              mountPath: /etc/nginx/nginx.conf
              subPath: nginx.conf

Match.

volumes.configMap

ConfigMap source
volumeMounts

Mount location
subPath

Single file, not refreshed
readOnly: true

Read-only

Next lesson: kubectl create configmap

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