ConfigMap¶

ConfigMap (ConfigMap) is an API object of Kubernetes, which is used to save non-confidential data into key-value pairs, and can store configurations that other objects need to use. When used, the container can use it as an environment variable, a command-line argument, or a configuration file in a storage volume. By using ConfigMaps, configuration data and application code can be separated, providing a more flexible way to modify application configuration.

scenes to be used¶

You can use ConfigMaps in Pods. There are many usage scenarios, mainly including:

• Use ConfigMaps to set the environment variables of the container

• Use ConfigMaps to set the command line parameters of the container

• Use ConfigMaps as container data volumes

Use ConfigMaps to set the environment variables of the container¶

You can use the ConfigMap as the environment variable of the container through the graphical interface or the terminal command line.

Graphical interface operation¶

When creating a workload through an image, you can set environment variables for the container by selecting Import ConfigMaps or Import ConfigMap Key Values on the Environment Variables interface.

1. Enter the Image Creation Workload page, in the Container Configuration step, select the Environment Variables configuration, and click the Add Environment Variable button.

2. Select ConfigMap Import or ConfigMap Key Value Import in the environment variable type.

   • When the environment variable type is selected as ConfigMap import, enter variable name, prefix name, ConfigMap name in sequence.

   • When the environment variable type is selected as ConfigMap key-value import, enter variable name, ConfigMap name, and key name in sequence.

Command line operation¶

You can set ConfigMaps as environment variables when creating a workload, using the valueFrom parameter to refer to the Key/Value in the ConfigMap.

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 reference ConfigMap
            configMapKeyRef:
              name: kpanda-configmap ##Referenced configuration file name
              key: SPECIAL_LEVEL ##referenced ConfigMap key
  restartPolicy: Never

Use ConfigMaps to set the command line parameters of the container¶

You can use ConfigMaps to set the command or parameter value in the container, and use the environment variable substitution syntax $(VAR_NAME) to do so. As follows.

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: kpanda-configmap
              key: SPECIAL_LEVEL
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: kpanda-configmap
              key: SPECIAL_TYPE
  restartPolicy: Never

After the Pod runs, the output is as follows.

Hello Kpanda

Use the ConfigMap as the data volume of the container¶

You can use the ConfigMap as the environment variable of the container through the graphical interface or the terminal command line.

Graphical operation¶

When creating a workload through an image, you can use the ConfigMap as the data volume of the container by selecting the storage type as "ConfigMap" on the "Data Storage" interface.

1. Enter the Image Creation Workload page, in the Container Configuration step, select the Data Storage configuration, and click the Add button in the Node Path Mapping list .

2. Select ConfigMap in the storage type, and enter container path, subpath and other information in sequence.

Command line operation¶

To use a ConfigMap in a Pod's storage volume.

Here is an example Pod that mounts a ConfigMap as a volume:

apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  -name: mypod
    image: redis
    volumeMounts:
    - name: foo
      mountPath: "/etc/foo"
      readOnly: true
  volumes:
  - name: foo
    configMap:
      name: myconfigmap

If there are multiple containers in a Pod, each container needs its own volumeMounts block, but you only need to set one spec.volumes block per ConfigMap.

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