Kubernetes equivalent of env-file in Docker

You can populate a container's environment variables through the use of Secrets or ConfigMaps. Use Secrets when the data you are working with is sensitive (e.g. passwords), and ConfigMaps when it is not.

In your Pod definition specify that the container should pull values from a Secret:

apiVersion: v1kind: Podmetadata:   labels:     context: docker-k8s-lab    name: mysql-pod  name: mysql-podspec:   containers:  - image: "mysql:latest"    name: mysql    ports:     - containerPort: 3306    envFrom:      - secretRef:         name: mysql-secret

Note that this syntax is only available in Kubernetes 1.6 or later. On an earlier version of Kubernetes you will have to specify each value manually, e.g.:

env: - name: MYSQL_USER  valueFrom:    secretKeyRef:      name: mysql-secret      key: MYSQL_USER

(Note that env take an array as value)

And repeating for every value.

Whichever approach you use, you can now define two different Secrets, one for production and one for dev.

dev-secret.yaml:

apiVersion: v1kind: Secretmetadata:  name: mysql-secrettype: Opaquedata:  MYSQL_USER: bXlzcWwK  MYSQL_PASSWORD: bXlzcWwK  MYSQL_DATABASE: c2FtcGxlCg==  MYSQL_ROOT_PASSWORD: c3VwZXJzZWNyZXQK

prod-secret.yaml:

apiVersion: v1kind: Secretmetadata:  name: mysql-secrettype: Opaquedata:  MYSQL_USER: am9obgo=  MYSQL_PASSWORD: c2VjdXJlCg==  MYSQL_DATABASE: cHJvZC1kYgo=  MYSQL_ROOT_PASSWORD: cm9vdHkK

And deploy the correct secret to the correct Kubernetes cluster:

kubectl config use-context devkubectl create -f dev-secret.yamlkubectl config use-context prodkubectl create -f prod-secret.yaml

Now whenever a Pod starts it will populate its environment variables from the values specified in the Secret.

A new update for Kubernetes(v1.6) allows what you asked for(years ago).

You can now use the envFrom like this in your yaml file:

  containers:  - name: django    image: image/name    envFrom:      - secretRef:         name: prod-secrets

Where development-secrets is your secret, you can create it by:

kubectl create secret generic prod-secrets --from-env-file=prod/env.txt`

Where the txt file content is a key-value:

DB_USER=username_hereDB_PASSWORD=password_here

The docs are still lakes of examples, I had to search really hard on those places:

• Secrets docs, search for --from-file - shows that this option is available.
• The equivalent ConfigMap docs shows an example on how to use it.

Note: there's a difference between --from-file and --from-env-file when creating secret as described in the comments below.

When defining a pod for Kubernetes using a YAML file, there's no direct way to specify a different file containing environment variables for a container. The Kubernetes project says they will improve this area in the future (see Kubernetes docs).

In the meantime, I suggest using a provisioning tool and making the pod YAML a template. For example, using Ansible your pod YAML file would look like:

file my-pod.yaml.template:

apiVersion: v1kind: Pod...spec:  containers:  ...    env:    - name: MYSQL_ROOT_PASSWORD      value: {{ mysql_root_pasword }}    ...

Then your Ansible playbook can specify the variable mysql_root_password somewhere convenient, and substitute it when creating the resource, for example:

file my-playbook.yaml:

- hosts: my_hosts  vars_files:   - my-env-vars-{{ deploy_to }}.yaml  tasks:  - name: create pod YAML from template    template: src=my-pod.yaml.template dst=my-pod.yaml  - name: create pod in Kubernetes    command: kubectl create -f my-pod.yaml

file my-env-vars-prod.yaml:

mysql_root_password: supersecret

file my-env-vars-test.yaml:

mysql_root_password: notsosecret

Now you create the pod resource by running, for example:

ansible-playbook -e deploy=test my-playbook.yaml