> ## 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.
# Environment Variables
> This article explains how to set environment variables in Kubernetes Pods using direct assignment and external sources like ConfigMaps and Secrets.
Kubernetes lets you inject configuration data into Pods via environment variables. This declarative approach mirrors Docker’s `-e` flag but offers tighter integration with Kubernetes primitives like ConfigMaps and Secrets.
## Why Use Environment Variables?
* Decouple configuration from container images
* Simplify application customization across environments
* Secure sensitive data using Secrets
## Prerequisites
* A running Kubernetes cluster
* `kubectl` configured against your cluster
* Basic knowledge of Pods and YAML manifests
***
## 1. Direct Assignment with `value`
To set an environment variable directly in your Pod spec, use the `env` array under the container definition:
```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
```
This makes `APP_COLOR=pink` available inside the container.
Direct assignment is ideal for non-sensitive, static configuration values.
You can replicate this behavior in Docker with:
```bash theme={null}
docker run -e APP_COLOR=pink simple-webapp-color
```
***
## 2. Decoupling Config with `valueFrom`
Rather than embedding values in your Pod spec, you can reference external sources:
```yaml theme={null}
env:
# From a ConfigMap
- name: APP_COLOR
valueFrom:
configMapKeyRef:
name: my-configmap
key: color.value
# From a Secret
- name: DB_PASSWORD
valueFrom:
secretKeyRef:
name: my-secret
key: db.password
```
Secrets are only base64-encoded by default and not encrypted at rest. Use encryption providers or external secret stores for stronger security.
***
## 3. Comparison at a Glance
| Configuration Source | Field | When to Use |
| -------------------- | --------------------------- | ------------------------------------------------ |
| Direct | `value` | Static, non-sensitive values |
| ConfigMap | `valueFrom.configMapKeyRef` | Application settings shared across Pods |
| Secret | `valueFrom.secretKeyRef` | Sensitive data (passwords, tokens, certificates) |
***
## 4. References
* [Kubernetes: Assign Environment Variables to Containers](https://kubernetes.io/docs/tasks/inject-data-application/define-environment-variable-container/)
* [Docker Environment Variables](https://docs.docker.com/engine/reference/run/#env-environment-variables)
* [ConfigMap Documentation](https://kubernetes.io/docs/concepts/configuration/configmap/)
* [Secrets Documentation](https://kubernetes.io/docs/concepts/configuration/secret/)