Use configuration items¶

Configuration item (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 configuration items, configuration data and application code can be separated, providing a more flexible way to modify application configuration.

scenes to be used¶

You can use configuration items in Pods. There are many use cases, mainly including:

• Use configuration items to set the environment variables of the container

• Use configuration items to set the command line parameters of the container

• Use configuration items as container data volumes

Set the environment variables of the container¶

You can use the configuration item 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 Configuration Items or Import Configuration Item Key Values on the Environment Variables interface.

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

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

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

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

Command line operation¶

You can set configuration items 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: # (1)
             configMapKeyRef:
               name: kpanda-configmap # (2)
               key: SPECIAL_LEVEL # (3)
   restartPolicy: Never

1. Use valueFrom to specify the value of the env reference configuration item
2. Referenced configuration file name
3. Referenced configuration item key

Set the command line parameters of the container¶

You can use configuration items 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

Used as container data volume¶

You can use the configuration item 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 configuration item as the data volume of the container by selecting the storage type as "Configuration Item" on the "Data Storage" interface.

1. Go to the Image Creation Workload page, in the Container Configuration step, select the Data Storage configuration, and click Add in theNode Path Mappinglist button.

2. Select Configuration Item 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.

Comments