Black lives matter.
We stand in solidarity with the Black community.
Racism is unacceptable.
It conflicts with the core values of the Kubernetes project and our community does not tolerate it.
We stand in solidarity with the Black community.
Racism is unacceptable.
It conflicts with the core values of the Kubernetes project and our community does not tolerate it.
This page shows how to define environment variables for a container in a Kubernetes Pod.
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, or you can use one of these Kubernetes playgrounds:
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 manifest for the
Pod:
pods/inject/envars.yaml
|
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|
Create a Pod based on that manifest:
kubectl apply -f https://k8s.io/examples/pods/inject/envars.yaml
List the running Pods:
kubectl get pods -l purpose=demonstrate-envars
The output is similar to:
NAME READY STATUS RESTARTS AGE
envar-demo 1/1 Running 0 9s
Get a shell to the container running in your Pod:
kubectl exec -it envar-demo -- /bin/bash
In your shell, run the printenv
command to list the environment variables.
# Run this in the shell inside the container
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
To exit the shell, enter exit
.
Note: The environment variables set using theenv
orenvFrom
field override any environment variables specified in the container image.
Note: The environment variables can reference each other, and cycles are possible, pay attention to the order before using
Environment variables that you define in a Pod's configuration can be used
elsewhere in the configuration, for example in commands and arguments that
you set for the Pod's containers.
In the example configuration below, the GREETING
, HONORIFIC
, and
NAME
environment variables are set to Warm greetings to
, The Most Honorable
, and Kubernetes
, respectively. Those environment variables
are then used in the CLI arguments passed to the env-print-demo
container.
apiVersion: v1
kind: Pod
metadata:
name: print-greeting
spec:
containers:
- name: env-print-demo
image: bash
env:
- name: GREETING
value: "Warm greetings to"
- name: HONORIFIC
value: "The Most Honorable"
- name: NAME
value: "Kubernetes"
command: ["echo"]
args: ["$(GREETING) $(HONORIFIC) $(NAME)"]
Upon creation, the command echo Warm greetings to The Most Honorable Kubernetes
is run on the container.