The following example shows how to use a ConfigMap.

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

When a ConfigMap is used in a workload, the workload and ConfigMap must be in the same cluster and namespace.
When a ConfigMap is mounted as a data volume and the ConfigMap is updated, Kubernetes updates the data in the data volume at the same time.
For a ConfigMap data volume mounted in subPath mode, Kubernetes cannot automatically update data in the data volume when the ConfigMap is updated.
When a ConfigMap is used as an environment variable, data is not automatically updated when the ConfigMap is updated. To update the data, restart the pod.

Configuring Environment Variables of a Workload

Using the CCE console

Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane, choose Workloads. In the dialog box displayed, click Create Workload in the upper right corner.
When creating a workload, click Environment Variables in the Container Settings area, and click Add Variable.
- Added from ConfigMap: Select a ConfigMap to import all of its keys as environment variables.
- Added from ConfigMap key: Import a key in a ConfigMap as the value of an environment variable.
  - Variable Name: name of an environment variable in the workload. The name can be customized and is set to the key name selected in the ConfigMap by default.
  - Variable Value/Reference: Select a ConfigMap and the key to be imported. The corresponding value is imported as a workload environment variable.
  For example, after you import the value Hello of SPECIAL_LEVEL in ConfigMap cce-configmap as the value of workload environment variable SPECIAL_LEVEL, an environment variable named SPECIAL_LEVEL with its value Hello exists in the container.
Configure other workload parameters and click Create Workload.
After the workload runs properly, log in to the container and run the following statement to check whether the ConfigMap has been set as an environment variable of the workload:
```
printenv SPECIAL_LEVEL
```
The example output is as follows:
```
Hello
```

Using kubectl

Use kubectl to access the cluster. For details, see Connecting to a Cluster Using kubectl.

Create a file named nginx-configmap.yaml and edit it.

vi nginx-configmap.yaml

Content of the YAML file:

Added from ConfigMap: 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 the workload.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-configmap
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-configmap
  template:
    metadata:
      labels:
        app: nginx-configmap
    spec:
      containers:
      - name: container-1
        image: nginx:latest
        envFrom:                      # Use envFrom to specify a ConfigMap to be referenced by environment variables.
        - configMapRef:
            name: cce-configmap       # Name of the referenced ConfigMap.
      imagePullSecrets:
      - name: default-secret

Added from ConfigMap key: When creating a workload, you can use a ConfigMap to set environment variables and use the valueFrom parameter to reference the key-value pair in the ConfigMap separately.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-configmap
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-configmap
  template:
    metadata:
      labels:
        app: nginx-configmap
    spec:
      containers:
      - name: container-1
        image: nginx:latest
        env:                             # Set the environment variable in the workload.
        - name: SPECIAL_LEVEL           # Name of the environment variable in the workload.
          valueFrom:                    # Specify a ConfigMap to be referenced by the environment variable.
            configMapKeyRef:
              name: cce-configmap       # Name of the referenced ConfigMap.
              key: SPECIAL_LEVEL        # Key in the referenced ConfigMap.
        - name: SPECIAL_TYPE            # Add multiple environment variables to import them at the same time.
          valueFrom:
            configMapKeyRef:
              name: cce-configmap
              key: SPECIAL_TYPE
      imagePullSecrets:
      - name: default-secret

Create a workload.
kubectl apply -f nginx-configmap.yaml
View the environment variables in the pod.
1. Run the following command to view the created pod:
```
kubectl get pod | grep nginx-configmap
```
  Expected output:
```
nginx-configmap-***   1/1     Running   0              2m18s
```
2. Run the following command to view the environment variables in the pod:
```
kubectl exec nginx-configmap-*** -- printenv SPECIAL_LEVEL SPECIAL_TYPE
```
  Expected output:
```
Hello
CCE
```
  The ConfigMap has been set as environment variables of the workload.

Configuring Command Line Parameters

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

Using the CCE console

Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane, choose Workloads. In the dialog box displayed, click Create Workload in the upper right corner.
When creating a workload, click Environment Variables in the Container Settings area, and click Add Variable. In this example, select Added from ConfigMap.
- Added from ConfigMap: Select a ConfigMap to import all of its keys as environment variables.
Click Lifecycle in the Container Settings area, click the Post-Start tab on the right, and set the following parameters:
- Processing Method: CLI
- Command: Enter the following three command lines. SPECIAL_LEVEL and SPECIAL_TYPE are the environment variable names in the workload, that is, the key names in the cce-configmap ConfigMap.
```
/bin/bash
-c
echo $SPECIAL_LEVEL $SPECIAL_TYPE > /usr/share/nginx/html/index.html
```
Configure other workload parameters and click Create Workload.
After the workload runs properly, log in to the container and run the following statement to check whether the ConfigMap has been set as an environment variable of the workload:
```
cat /usr/share/nginx/html/index.html
```
The example output is as follows:
```
Hello CCE
```

Using kubectl

Use kubectl to access the cluster. For details, see Connecting to a Cluster Using kubectl.

Create a file named nginx-configmap.yaml and edit it.

vi nginx-configmap.yaml

As shown in the following example, the cce-configmap ConfigMap is imported to the workload. SPECIAL_LEVEL and SPECIAL_TYPE are the environment variable names in the workload, that is, the key names in the cce-configmap ConfigMap.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-configmap
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-configmap
  template:
    metadata:
      labels:
        app: nginx-configmap
    spec:
      containers:
      - name: container-1
        image: nginx:latest
        lifecycle:
          postStart:
            exec:
              command: [ "/bin/sh", "-c", "echo $SPECIAL_LEVEL $SPECIAL_TYPE > /usr/share/nginx/html/index.html" ]
        envFrom:                      # Use envFrom to specify a ConfigMap to be referenced by environment variables.
        - configMapRef:
            name: cce-configmap       # Name of the referenced ConfigMap.
      imagePullSecrets:
        - name: default-secret

Create a workload.
kubectl apply -f nginx-configmap.yaml
After the workload runs properly, the following content is entered into the /usr/share/nginx/html/index.html file in the container:
1. Run the following command to view the created pod:
```
kubectl get pod | grep nginx-configmap
```
  Expected output:
```
nginx-configmap-***   1/1     Running   0              2m18s
```
2. Run the following command to view the environment variables in the pod:
```
kubectl exec nginx-configmap-*** -- cat /usr/share/nginx/html/index.html
```
  Expected output:
```
Hello CCE
```

Mounting a ConfigMap to the Workload Data Volume

The data stored in a ConfigMap can be referenced in a volume of type ConfigMap. You can mount such a volume to a specified container path. The platform supports the separation of workload codes and configuration files. ConfigMap volumes are used to store workload configuration parameters. Before that, create ConfigMaps in advance. For details, see Creating a ConfigMap.

Using the CCE console

Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane, choose Workloads. In the dialog box displayed, click Create Workload in the upper right corner.
When creating a workload, click Data Storage in the Container Settings area. Click Add Volume and select ConfigMap from the drop-down list.

Select parameters for mounting a ConfigMap volume, as shown in Table 1.

**Table 1** Mounting a ConfigMap volume
Parameter	Description
ConfigMap	Select the desired ConfigMap. A ConfigMap must be created beforehand. For details, see Creating a ConfigMap.
Mount Path	Enter a mount point. After the ConfigMap volume is mounted, a configuration file with the key as the file name and value as the file content is generated in the mount path of the container. This parameter specifies a container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. This may lead to container errors. Mount the volume to an empty directory. If the directory is not empty, ensure that there are no files that affect container startup. Otherwise, the files will be replaced, which leads to a container startup failure or workload creation failure. NOTICE: If the container is mounted to a high-risk directory, use an account with minimum permissions to start the container. Otherwise, high-risk files on the host may be damaged.
Subpath	Enter a subpath of the mount path. A subpath is used to mount a local volume so that the same data volume is used in a single pod. If this parameter is left blank, the root path is used by default. The subpath can be the key and value of a ConfigMap or secret. If the subpath is a key-value pair that does not exist, the data import does not take effect. The data imported by specifying a subpath will not be updated along with the ConfigMap/secret updates.
Permission	Read-only, indicating that data volume in the path is read-only.

After the configuration, click Create Workload.
After the workload runs properly, the SPECIAL_LEVEL and SPECIAL_TYPE files will be generated in the /etc/config directory in this example. The contents of the files are Hello and CCE, respectively.

Access the container and run the following statement to view the SPECIAL_LEVEL or SPECIAL_TYPE file in the container:
```
cat /etc/config/SPECIAL_LEVEL
```
Expected output:
```
Hello
```

Using kubectl

Use kubectl to access the cluster. For details, see Connecting to a Cluster Using kubectl.

Create a file named nginx-configmap.yaml and edit it.

vi nginx-configmap.yaml

As shown in the following example, after the ConfigMap volume is mounted, a configuration file with the key as the file name and value as the file content is generated in the /etc/config directory of the container.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-configmap
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-configmap
  template:
    metadata:
      labels:
        app: nginx-configmap
    spec:
      containers:
      - name: container-1
        image: nginx:latest
        volumeMounts:
        - name: config-volume
          mountPath: /etc/config            # Mount to the /etc/config directory.
          readOnly: true
    volumes:
    - name: config-volume
      configMap:
        name: cce-configmap                 # Name of the referenced ConfigMap.

Create a workload.
kubectl apply -f nginx-configmap.yaml
After the workload runs properly, the SPECIAL_LEVEL and SPECIAL_TYPE files will be generated in the /etc/config directory. The contents of the files are Hello and CCE, respectively.
1. Run the following command to view the created pod:
```
kubectl get pod | grep nginx-configmap
```
  Expected output:
```
nginx-configmap-***   1/1     Running   0              2m18s
```
2. Run the following command to view the SPECIAL_LEVEL or SPECIAL_TYPE file in the pod:
```
kubectl exec nginx-configmap-*** -- cat /etc/config/SPECIAL_LEVEL
```
  Expected output:
```
Hello
```

Using a ConfigMap

Configuring Environment Variables of a Workload

Configuring Command Line Parameters

Mounting a ConfigMap to the Workload Data Volume