Tasks

Step-by-step instructions for performing operations with Kubernetes.

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Defining Environment Variables for a Container

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

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube.

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 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:

envars.yaml
apiVersion: v1
kind: Pod
metadata:
  name: envar-demo
  labels:
    purpose: demonstrate-envars
spec:
  containers:
  - name: envar-demo-container
    image: gcr.io/google-samples/node-hello:1.0
    env:
    - name: DEMO_GREETING
      value: "Hello from the environment"
  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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