Configuring Environment Variables in Applications

In this lesson you’ll learn how to set environment variables for containers running in Kubernetes and how that maps from the typical Docker -e pattern.

Quick comparison: Docker vs Kubernetes

When running a container locally with Docker you can pass environment variables using -e:

# Pass APP_COLOR to a container with Docker
docker run -e APP_COLOR=pink simple-webapp-color

In Kubernetes, you configure environment variables inside the container spec of a Pod, Deployment, or other workload manifest using the env (or envFrom) fields.

Use env for individual variables (static or referenced), and envFrom to import all keys from a ConfigMap or Secret. The same env configuration works inside any workload that has a containers spec (Pod, Deployment, ReplicaSet, etc.).

Basic example — key/value in a Pod manifest

Add an env array to the container spec. Each item uses name and value. This example shows a direct, static environment variable:

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"

Notes:

env is an array, so each environment variable is prefixed with -.
The same env entries can be put into a containers entry inside a Deployment manifest.

Referencing ConfigMaps and Secrets

Instead of hardcoding values, reference keys from a ConfigMap or Secret using valueFrom. This is the preferred pattern for separating configuration and secrets from container images. Example referencing a key from a ConfigMap:

env:
- name: APP_COLOR
  valueFrom:
    configMapKeyRef:
      name: color-config
      key: APP_COLOR

Example referencing a key from a Secret:

env:
- name: APP_COLOR
  valueFrom:
    secretKeyRef:
      name: color-secret
      key: APP_COLOR

Importing all keys with envFrom

If you want to expose every key from a ConfigMap or Secret as environment variables, use envFrom. This will create one environment variable per key in the referenced object.

envFrom:
- configMapRef:
    name: color-config
# or
- secretRef:
    name: color-secret

When to use each approach

Method	Use case	Example
Static `env` with `value`	Simple, unchanging values or demos	See Pod manifest above
`valueFrom.configMapKeyRef`	Single config key from a ConfigMap	`configMapKeyRef: name: color-config key: APP_COLOR`
`valueFrom.secretKeyRef`	Single secret key (sensitive)	`secretKeyRef: name: color-secret key: APP_COLOR`
`envFrom`	Import all keys from a ConfigMap or Secret (convenient but broad)	`envFrom: - configMapRef: name: color-config`

Security reminder

Secrets in Kubernetes are base64-encoded, not encrypted by default (see Kubernetes documentation: https://kubernetes.io/docs/concepts/configuration/secret/). Treat them as sensitive and consider using appropriate secrets management (encryption at rest, RBAC controls, or external secret stores) for production workloads.

Links and references

Kubernetes ConfigMap: https://kubernetes.io/docs/concepts/configuration/configmap/
Kubernetes Secret: https://kubernetes.io/docs/concepts/configuration/secret/
Kubernetes Pods and Containers: https://kubernetes.io/docs/concepts/workloads/pods/

That’s it — you’ve seen the common patterns to inject environment variables into containers in Kubernetes and when to use static values, ConfigMaps, Secrets, or envFrom.

Introduction

Core Concepts

Scheduling

Logging & Monitoring

Application Lifecycle Management

Cluster Maintenance

Security

Storage

Networking

Design and Install a Kubernetes Cluster

Install "Kubernetes the kubeadm way"

Troubleshooting

Helm Basics (2025 Updates)

Kustomize Basics (2025 Updates)

Other Topics

Mock Exams

Configuring Environment Variables in Applications

Quick comparison: Docker vs Kubernetes

Basic example — key/value in a Pod manifest

Referencing ConfigMaps and Secrets

Importing all keys with envFrom

When to use each approach

Security reminder

Links and references

Watch Video

​Quick comparison: Docker vs Kubernetes

​Basic example — key/value in a Pod manifest

​Referencing ConfigMaps and Secrets

​Importing all keys with envFrom

​When to use each approach

​Security reminder

​Links and references

Watch Video

Quick comparison: Docker vs Kubernetes

Basic example — key/value in a Pod manifest

Referencing ConfigMaps and Secrets

Importing all keys with envFrom

When to use each approach

Security reminder

Links and references