> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Configure Environment Variables in Applications
> This article explores configuring environment variables for applications in Kubernetes, including Docker examples and using ConfigMaps and Secrets for better management.
In this article, we'll explore how to configure environment variables for applications deployed with Kubernetes. First, we review a basic Docker example that establishes an environment variable, then we demonstrate how to specify environment variables directly within a Kubernetes pod manifest. This guide is essential for developers looking to streamline container configuration and deployment.
## Setting Environment Variables Using Docker
When running a Docker container, you can set environment variables using the `-e` flag. For example, the command below sets the `APP_COLOR` environment variable to "pink":
```bash theme={null}
docker run -e APP_COLOR=pink simple-webapp-color
```
This command assigns the value "pink" to `APP_COLOR` while launching the `simple-webapp-color` container.
## Configuring Environment Variables in Kubernetes Pods
Kubernetes allows you to define environment variables within your pod definitions. In the pod manifest, environment variables are listed under the `env` property, which is an array. Each entry in the array should specify:
* `name`: The name of the environment variable.
* `value`: The corresponding value assigned to that environment variable.
Below is an example pod definition that explicitly sets the environment variable:
```yaml theme={null}
apiVersion: v1
kind: Pod
metadata:
name: simple-webapp-color
spec:
containers:
- name: simple-webapp-color
image: simple-webapp-color
ports:
- containerPort: 8080
env:
- name: APP_COLOR
value: pink
```
In this configuration, the container running the `simple-webapp-color` image will have `APP_COLOR` set to "pink".
## Leveraging ConfigMaps and Secrets for Environment Variables
Instead of hardcoding values into your pod manifest, you can enhance flexibility and security by referencing external configuration sources such as ConfigMaps or Secrets. This approach simplifies maintenance and helps protect sensitive information.
To define an environment variable directly, use:
```yaml theme={null}
env:
- name: APP_COLOR
value: pink
```
To reference a ConfigMap for the environment variable, update the definition as follows:
```yaml theme={null}
env:
- name: APP_COLOR
valueFrom:
configMapKeyRef:
name: app-config
key: color
```
Similarly, to source the environment variable from a Secret, configure it like this:
```yaml theme={null}
env:
- name: APP_COLOR
valueFrom:
secretKeyRef:
name: app-secrets
key: color
```
In both cases, Kubernetes retrieves the value for `APP_COLOR` from the specified external resource.
Using ConfigMaps and Secrets promotes better security practices and easier management of configuration drift. Ensure these objects are updated consistently with your application requirements.
Avoid hardcoding sensitive data directly into your manifests. Always use Secrets when dealing with sensitive information such as passwords or API keys.
## Summary
In this article, we covered:
* How to set environment variables using a Docker command.
* Defining environment variables within Kubernetes pod definitions.
* The benefits of leveraging ConfigMaps and Secrets for managing environment configurations.
For additional details and best practices, visit [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/).
That concludes this guide. In our next article, we will explore more advanced Kubernetes configuration techniques, further enhancing your container orchestration capabilities.