cloud-container-engine/umn/source/configuration_center/using_a_configmap.rst

original_name

cce_01_0015.html

Using a ConfigMap

• Setting Workload Environment Variables <cce_01_0015__section1737733192813>
• Setting Command Line Parameters <cce_01_0015__section17930105710189>
• Attaching a ConfigMap to the Workload Data Volume <cce_01_0015__section1490261161916>

The following example shows how to use a ConfigMap.

apiVersion: v1
kind: ConfigMap
metadata:
  name: cce-configmap
data:
  SPECIAL_LEVEL: Hello
  SPECIAL_TYPE: CCE

Important

When a ConfigMap is used in a pod, the pod and ConfigMap must be in the same cluster and namespace.

Setting Workload Environment Variables

When creating a workload, you can use a ConfigMap to set environment variables. The valueFrom parameter indicates the key-value pair to be referenced.

apiVersion: v1
kind: Pod
metadata:
  name: configmap-pod-1
spec:
  containers:
    - name: test-container
      image: busybox
      command: [ "/bin/sh", "-c", "env" ]
      env:
        - name: SPECIAL_LEVEL_KEY
          valueFrom:                             ## Use valueFrom to specify the value of the env that refers to the ConfigMap.
            configMapKeyRef:
              name: cce-configmap                ## Name of the referenced configuration file.
              key: SPECIAL_LEVEL                 ## Key of the referenced ConfigMap.
  restartPolicy: Never

If you need to define the values of multiple ConfigMaps as the environment variables of the pods, add multiple environment variable parameters to the pods.

env:
- name: SPECIAL_LEVEL_KEY
  valueFrom:
    configMapKeyRef:
          name: cce-configmap
          key: SPECIAL_LEVEL
- name: SPECIAL_TYPE_KEY
  valueFrom:
    configMapKeyRef:
          name: cce-configmap
          key: SPECIAL_TYPE

To add all data in a ConfigMap to environment variables, use the envFrom parameter. The keys in the ConfigMap will become names of environment variables in a pod.

apiVersion: v1
kind: Pod
metadata:
  name: configmap-pod-2
spec:
  containers:
    - name: test-container
      image: busybox
      command: [ "/bin/sh", "-c", "env" ]
      envFrom:
      - configMapRef:
          name: cce-configmap
  restartPolicy: Never

Setting Command Line Parameters

You can use a ConfigMap to set commands or parameter values for a container by using the environment variable substitution syntax $(VAR_NAME). The following shows an example.

apiVersion: v1
kind: Pod
metadata:
  name: configmap-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: cce-configmap
              key: SPECIAL_LEVEL
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: cce-configmap
              key: SPECIAL_TYPE
  restartPolicy: Never

After the pod runs, the following information is displayed:

Hello CCE

Attaching a ConfigMap to the Workload Data Volume

A ConfigMap can also be used in the data volume. You only need to attach the ConfigMap to the workload when creating the workload. After the mounting is complete, a configuration file with key as the file name and value as the file content is generated.

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

After the pod is run, the SPECIAL_LEVEL and SPECIAL_TYPE files are generated in the /etc/config directory. The contents of the files are Hello and CCE, respectively. Also, the following file names will be displayed.

SPECIAL_TYPE
SPECIAL_LEVEL

To mount a ConfigMap to a data volume, you can also perform operations on the CCE console. When creating a workload, set advanced settings for the container, choose Data Storage > Local Volume, click Add Local Volume, and select ConfigMap. For details, see ConfigMap <cce_01_0053__en-us_topic_0000001199341206_section18638191594712>.