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 is updated, Kubernetes updates the data in the data volume at the same time.
When a ConfigMap data volume mounted in subPath mode is updated, Kubernetes cannot automatically update the data in the data volume.
When a ConfigMap is used as an environment variable, data can not be automatically updated when the ConfigMap is updated. To update the data, you need to restart the pod.

Setting Workload Environment Variables

Using the console

Log in to the CCE console and access the cluster console.
In the navigation pane, choose Workloads. Then, click Create Workload.
When creating a workload, click Environment Variables in the Container Settings area, and click .
- 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, access the container and run the following command 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

According to Connecting to a Cluster Using kubectl, configure the kubectl command to connect an ECS to the cluster.

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 a pod.

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 a 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 environment variables in the workload.
        - name: SPECIAL_LEVEL           # Name of the environment variable in the workload.
          valueFrom:                    # Use valueFrom to specify an environment variable to reference a ConfigMap.
            configMapKeyRef:
              name: cce-configmap       # Name of the referenced ConfigMap.
              key: SPECIAL_LEVEL        # Key in the referenced ConfigMap.
        - name: SPECIAL_TYPE            # Add multiple environment variables. Multiple environment variables can be imported 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 an environment variable of the workload.

Setting 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 console

Log in to the CCE console and access the cluster console.
In the navigation pane, choose Workloads. Then, click Create Workload.
When creating a workload, click Environment Variables in the Container Settings area, and click . 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, access the container and run the following command 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

According to Connecting to a Cluster Using kubectl, configure the kubectl command to connect an ECS to the cluster.

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 environment variable names, that is, 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
```

Attaching 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, you need to create ConfigMaps in advance. For details, see Creating a ConfigMap.

Using the console

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

Set the local volume type to ConfigMap and set parameters for adding a local volume, as shown in Table 1.

**Table 1** Mounting a ConfigMap volume
Parameter	Description
Option	Select the desired ConfigMap name. A ConfigMap must be created in advance. For details, see Creating a ConfigMap.
Add Container Path	Configure the following parameters: Container Path: Enter the path of the container, for example, /tmp. This parameter indicates the 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 action may cause container errors. You are advised to mount the container to an empty directory. If the directory is not empty, ensure that there are no files affecting container startup in the directory. Otherwise, such files will be replaced, resulting in failures to start the container and create the workload. NOTICE: When the container is mounted to a high-risk directory, you are advised to use an account with minimum permissions to start the container; otherwise, high-risk files on the host machine may be damaged. subPath: Enter a subpath, for example, tmp. A subpath is used to mount a local volume so that the same data volume is used in a single pod. 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. Set the permission to Read-only. Data volumes in the path are read-only. You can click to add multiple paths and subpaths.

Using kubectl

According to Connecting to a Cluster Using kubectl, configure the kubectl command to connect an ECS to the cluster.

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 are 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-*** -- /etc/config/SPECIAL_LEVEL
```
  Expected output:
```
Hello
```

Using a ConfigMap

Setting Workload Environment Variables

Setting Command Line Parameters

Attaching a ConfigMap to the Workload Data Volume