Use a ConfigMap in a pod

Limits

To use a ConfigMap in a pod, make sure that the ConfigMap and pod are in the same cluster and namespace.

Create a ConfigMap

In this example, a ConfigMap named special_config is created. This ConfigMap consists of two key-value pairs: SPECIAL_LEVEL: very and SPECIAL_TYPE: charm.

apiVersion: v1
kind: ConfigMap
metadata:
   name: special-config
   namespace: default
data:
   SPECIAL_LEVEL: very
   SPECIAL_TYPE: charm

Use a ConfigMap to define environment variables for a pod.

Use the key-value pairs of a ConfigMap to define environment variables for a pod

1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of a cluster or click Details in the Actions column. The details page of the cluster appears.
4. In the left-side navigation pane, click Workload.
5. In the upper-right corner of the Deployments tab, click Create from Template.
6. Select the sample template or enter a custom template, and click Create.

   To define an environment variable for a pod, you can use the valueFrom field to reference the value of SPECIAL_LEVEL.

   The following code block is an example:

   apiVersion: v1
   kind: Pod
   metadata:
      name: config-pod-1
   spec:
      containers:
        - name: test-container
          image: busybox
          command: [ "/bin/sh", "-c", "env" ]
          env:
            - name: SPECIAL_LEVEL_KEY
              valueFrom:              ##Use valueFrom to denote that env references the value of a ConfigMap.
                configMapKeyRef:
                  name: special-config               ##The name of the referenced ConfigMap.
                  key: SPECIAL_LEVEL                 ##The key of the referenced key-value pair.
      restartPolicy: Never

Use all key-value pairs of a ConfigMap to define multiple environment variables for a pod

1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of a cluster or click Details in the Actions column. The details page of the cluster appears.
4. In the left-side navigation pane, click Workload.
5. In the upper-right corner of the Deployments tab, click Create from Template.
6. Select the sample template or enter a custom template, and click Create.

   To use all key-value pairs of a ConfigMap to define multiple environment variables for a pod, you can use the envFrom parameter. The keys of the ConfigMap are used as the names of the environment variables.

   The following code block is an example:

   apiVersion: v1
   kind: Pod
   metadata:
      name: config-pod-2
   spec:
      containers:
        - name: test-container
          image: busybox
          command: [ "/bin/sh", "-c", "env" ]
          envFrom:                ##All key-value pairs of the special-config ConfigMap are referenced.
          - configMapRef:
              name: special-config
      restartPolicy: Never

Use a ConfigMap to set command line parameters

1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of a cluster or click Details in the Actions column. The details page of the cluster appears.
4. In the left-side navigation pane, click Workload.
5. In the upper-right corner of the Deployments tab, click Create from Template.
6. Select the sample template or enter a custom template, and click Create.

   You can use ConfigMaps to define the commands or parameter values for a container by using the environment variable replacement syntax $(VAR_NAME).

   The following code block is an example:

   apiVersion: v1
   kind: Pod
   metadata:
      name: config-pod-3
   spec:
      containers:
        - name: test-container
          image: busybox
          command: [ "/bin/sh", "-c", "echo $(SPECIAL_LEVEL_KEY) $(SPECIAL_TYPE_KEY)" ]
          env:
            - name: SPECIAL_LEVEL_KEY
              valueFrom:
                configMapKeyRef:
                  name: special-config
                  key: SPECIAL_LEVEL
            - name: SPECIAL_TYPE_KEY
              valueFrom:
                configMapKeyRef:
                  name: special-config
                  key: SPECIAL_TYPE
      restartPolicy: Never

Use a ConfigMap in a volume

1. In the left-side navigation pane, click Clusters.
2. On the Clusters page, click the name of a cluster or click Details in the Actions column. The details page of the cluster appears.
3. In the left-side navigation pane, click Workload.
4. In the upper-right corner of the Deployments tab, click Create from Template.
5. Select the sample template or enter a custom template, and click Create.
   To use a ConfigMap in a volume, specify the name of the ConfigMap in the volumes section. This saves the key-value pairs of the ConfigMap to the directory specified by mountPath. In this example, the directory is /etc/config. Configuration files that are named after the keys of the key-value pairs of the ConfigMap are generated. The values of the key-value pairs are stored in the related files.

   The following code block is an example:

   apiVersion: v1
   kind: Pod
   metadata:
      name: config-pod-4
   spec:
      containers:
        - name: test-container
          image: busybox
          command: [ "/bin/sh", "-c", "ls /etc/config/" ]   ##List the files in the directory.
          volumeMounts:
          - name: config-volume
            mountPath: /etc/config
      volumes:
        - name: config-volume
          configMap:
            name: special-config
      restartPolicy: Never

   After you run the pod, the following output is returned:

   SPECIAL_TYPE
   SPECIAL_LEVEL