website/content/en/docs/tasks/inject-data-application/define-environment-variable-container.md

title	content_template	weight
Define Environment Variables for a Container	templates/task	20

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This page shows how to define environment variables for a container in a Kubernetes Pod.

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Define an environment variable for a container

When you create a Pod, you can set environment variables for the containers that run in the Pod. To set environment variables, include the env or envFrom field in the configuration file.

In this exercise, you create a Pod that runs one container. The configuration file for the Pod defines an environment variable with name DEMO_GREETING and value "Hello from the environment". Here is the configuration file for the Pod:

{{< code file="envars.yaml" >}}

1. Create a Pod based on the YAML configuration file:

   kubectl create -f https://k8s.io/docs/tasks/inject-data-application/envars.yaml
   

2. List the running Pods:

   kubectl get pods -l purpose=demonstrate-envars
   

   The output is similar to this:

    NAME            READY     STATUS    RESTARTS   AGE
    envar-demo      1/1       Running   0          9s
   

3. Get a shell to the container running in your Pod:

   kubectl exec -it envar-demo -- /bin/bash
   

4. In your shell, run the printenv command to list the environment variables.

   root@envar-demo:/# printenv
   

   The output is similar to this:

    NODE_VERSION=4.4.2
    EXAMPLE_SERVICE_PORT_8080_TCP_ADDR=10.3.245.237
    HOSTNAME=envar-demo
    ...
    DEMO_GREETING=Hello from the environment
    DEMO_FAREWELL=Such a sweet sorrow
   

5. To exit the shell, enter exit.

{{< note >}} Note: The environment variables set using the env or envFrom field will override any environment variables specified in the container image. {{< /note >}}

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• Learn more about environment variables.
• Learn about using secrets as environment variables.
• See [EnvVarSource](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#envvarsource-v1-core).

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