# Define Environment Variable Values Using An Init Container
LLMS index: [llms.txt](/llms.txt)
---
FEATURE STATE:
Kubernetes v1.35 [beta](enabled by default)
This page show how to configure environment variables for containers in a Pod via file.
## Before you begin
You need to have a Kubernetes cluster, and the kubectl command-line tool must
be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a
cluster, you can create one by using
minikube
or you can use one of these Kubernetes playgrounds:
Your Kubernetes server must be at or later than version v1.34.
To check the version, enter kubectl version.
## How the design works
In this exercise, you will create a Pod that sources environment variables from files,
projecting these values into the running container.
apiVersion: v1
kind: Pod
metadata:
name: envfile-test-pod
spec:
initContainers:
- name: setup-envfile
image: nginx
command: ['sh', '-c', "echo \"DB_ADDRESS=\'address\'\nREST_ENDPOINT=\'endpoint\'\" > /data/config.env"]
volumeMounts:
- name: config
mountPath: /data
containers:
- name: use-envfile
image: nginx
command: [ "/bin/sh", "-c", "env" ]
env:
- name: DB_ADDRESS
valueFrom:
fileKeyRef:
path: config.env
volumeName: config
key: DB_ADDRESS
optional: false
restartPolicy: Never
volumes:
- name: config
emptyDir: {}
In this manifest, you can see the `initContainer` mounts an `emptyDir` volume and writes environment variables to a file within it,
and the regular containers reference both the file and the environment variable key
through the `fileKeyRef` field without needing to mount the volume.
When `optional` field is set to false, the specified `key` in `fileKeyRef` must exist in the environment variables file.
The volume will only be mounted to the container that writes to the file
(`initContainer`), while the consumer container that consumes the environment variable will not have the volume mounted.
The env file format adheres to the [kubernetes env file standard](/docs/tasks/inject-data-application/define-environment-variable-via-file/#env-file-syntax).
During container initialization, the kubelet retrieves environment variables
from specified files in the `emptyDir` volume and exposes them to the container.
Note:
All container types (initContainers, regular containers, sidecars containers,
and ephemeral containers) support environment variable loading from files.
While these environment variables can store sensitive information,
emptyDir volumes don't provide the same protection mechanisms as
dedicated Secret objects. Therefore, exposing confidential environment variables
to containers through this feature is not considered a security best practice.
