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

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+---
+title: Define Environment Variables for a Container
+content_template: templates/task
+---
+
+{{% capture overview %}}
+
+This page shows how to define environment variables when you run a container
+in a Kubernetes Pod.
+
+{{% /capture %}}
+
+
+{{% capture prerequisites %}}
+
+{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
+
+{{% /capture %}}
+
+
+{{% capture steps %}}
+
+## 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
+
+1. 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
+
+1. Get a shell to the container running in your Pod:
+
+       kubectl exec -it envar-demo -- /bin/bash
+
+1. 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
+
+1. 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 >}}
+
+{{% /capture %}}
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+
+* Learn more about [environment variables](/docs/tasks/configure-pod-container/environment-variable-expose-pod-information/).
+* Learn about [using secrets as environment variables](/docs/user-guide/secrets/#using-secrets-as-environment-variables).
+* See [EnvVarSource](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#envvarsource-v1-core).
+
+{{% /capture %}}
+
+
+