website/docs/tasks/configure-pod-container/define-environment-variable-container.md

title
Defining Environment Variables for a Container

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This page shows how to define environment variables when you run a container in a Kubernetes Pod.

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Defining 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 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:

{% include code.html language="yaml" file="envars.yaml" ghlink="/docs/tasks/configure-pod-container/envars.yaml" %}

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

    kubectl create -f http://k8s.io/docs/tasks/configure-pod-container/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
   

5. To exit the shell, enter exit.

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• Learn more about environment variables.
• Learn about using secrets as environment variables.
• See EnvVarSource.

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