How to pull environment variables with Helm charts - kubernetes

Question

I have my deployment.yaml file within the templates directory of Helm charts with several environment variables for the container I will be running using Helm.
Now I want to be able to pull the environment variables locally from whatever machine the helm is ran so I can hide the secrets that way.
How do I pass this in and have helm grab the environment variables locally when I use Helm to run the application?
Here is some part of my deployment.yaml file
...
...
spec:
restartPolicy: Always
containers:
- name: sample-app
image: "sample-app:latest"
imagePullPolicy: Always
env:
- name: "USERNAME"
value: "app-username"
- name: "PASSWORD"
value: "28sin47dsk9ik"
...
...
How can I pull the value of USERNAME and PASSWORD from local environment variables when I run helm?
Is this possible? If yes, then how do I do this?

Answer 1

You can export the variable and use it while running helm install.
Before that, you have to modify your chart so that the value can be set while installation.
Skip this part, if you already know, how to setup template fields.
As you don't want to expose the data, so it's better to have it saved as secret in kubernetes.
First of all, add this two lines in your Values file, so that these two values can be set from outside.
username: root
password: password
Now, add a secret.yaml file inside your template folder. and, copy this code snippet into that file.
apiVersion: v1
kind: Secret
metadata:
name: {{ .Release.Name }}-auth
data:
password: {{ .Values.password | b64enc }}
username: {{ .Values.username | b64enc }}
Now tweak your deployment yaml template and make changes in env section, like this
...
...
spec:
restartPolicy: Always
containers:
- name: sample-app
image: "sample-app:latest"
imagePullPolicy: Always
env:
- name: "USERNAME"
valueFrom:
secretKeyRef:
key: username
name: {{ .Release.Name }}-auth
- name: "PASSWORD"
valueFrom:
secretKeyRef:
key: password
name: {{ .Release.Name }}-auth
...
...
If you have modified your template correctly for --set flag,
you can set this using environment variable.
$ export USERNAME=root-user
Now use this variable while running helm install,
$ helm install --set username=$USERNAME ./mychart
If you run this helm install in dry-run mode, you can verify the changes,
$ helm install --dry-run --set username=$USERNAME --debug ./mychart
[debug] Created tunnel using local port: '44937'
[debug] SERVER: "127.0.0.1:44937"
[debug] Original chart version: ""
[debug] CHART PATH: /home/maruf/go/src/github.com/the-redback/kubernetes-yaml-drafts/helm-charts/mychart
NAME: irreverant-meerkat
REVISION: 1
RELEASED: Fri Apr 20 03:29:11 2018
CHART: mychart-0.1.0
USER-SUPPLIED VALUES:
username: root-user
COMPUTED VALUES:
password: password
username: root-user
HOOKS:
MANIFEST:
---
# Source: mychart/templates/secret.yaml
apiVersion: v1
kind: Secret
metadata:
name: irreverant-meerkat-auth
data:
password: password
username: root-user
---
# Source: mychart/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: irreverant-meerkat
labels:
app: irreverant-meerkat
spec:
replicas: 1
template:
metadata:
name: irreverant-meerkat
labels:
app: irreverant-meerkat
spec:
containers:
- name: irreverant-meerkat
image: alpine
env:
- name: "USERNAME"
valueFrom:
secretKeyRef:
key: username
name: irreverant-meerkat-auth
- name: "PASSWORD"
valueFrom:
secretKeyRef:
key: password
name: irreverant-meerkat-auth
imagePullPolicy: IfNotPresent
restartPolicy: Always
selector:
matchLabels:
app: irreverant-meerkat
You can see that the data of username in secret has changed to root-user.
I have added this example into github repo.
There is also some discussion in kubernetes/helm repo regarding this. You can see this issue to know about all other ways to use environment variables.

Answer 2

you can pass env key value from the value yaml by setting the deployment yaml as below :
spec:
restartPolicy: Always
containers:
- name: sample-app
image: "sample-app:latest"
imagePullPolicy: Always
env:
{{- range $name, $value := .Values.env }}
- name: {{ $name }}
value: {{ $value }}
{{- end }}
in the values.yaml :
env:
- name: "USERNAME"
value: ""
- name: "PASSWORD"
value: ""
when you install the chart you can pass the username password value
helm install chart_name --name release_name --set env.USERNAME="app-username" --set env.PASSWORD="28sin47dsk9ik"

Answer 3

For those looking to use data structures instead lists for their env variable files, this has worked for me:
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
env:
{{- range $key, $val := .Values.env }}
- name: {{ $key }}
value: {{ $val | quote }}
{{- end }}
values.yaml:
env:
FOO: "BAR"
USERNAME: "CHANGEME"
PASWORD: "CHANGEME"
That way I can access specific values by name in other parts of the helm chart and pass the sensitive values via helm command line.

Answer 4

To get away from having to set each secret manually, you can use:
export MY_SECRET=123
envsubst < values.yaml | helm install my-release . --values -
where ${MY_SECRET} is referenced in your values.yaml file like:
mychart:
secrets:
secret_1: ${MY_SECRET}

Answer 5

Helm 3.1 supports post rendering (https://helm.sh/docs/topics/advanced/#post-rendering) which passes the manifest to a script before it is actually send to Kubernetes API. Post rendering allows to manipulate the manifest in multiple ways (e.g. use kustomize on top of Helm).
The simplest form of a post renderer which replaces predefined environment values could look like this:
#!/bin/sh
envsubst <&0
Note this will replace every occurance of $<VARNAME> which could collide with variables in the templates like shell scripts in liveness probes. So better explicitly define the variables you want to get replaced: envsubst '${USERNAME} ${PASSWORD}' <&0
Define your env variables in the shell:
export USERNAME=john PASSWORD=my-secret
In the tempaltes (e.g. secret.yaml) use the values defined in the values.yaml:
apiVersion: v1
kind: Secret
metadata:
name: {{ .Release.Name }}-auth
data:
username: {{ .Values.username }}
password: {{ .Values.password }}
Note that you can not apply string transformations like b64enc on the strings as the get injected in the manifest after Helm has already processed all YAML files. Instead you can encode them in the post renderer if required.
In the values.yaml use the variable placeholders:
...
username: ${USERNAME}
password: ${PASSWORD}
The parameter --post-renderer is supported in several Helm commands e.g.
helm install --dry-run --post-renderer ./my-post-renderer.sh my-chart
By using the post renderer the variables/placeholders automatically get replaced by envsubst without additional scripting.

Answer 6

i guess the question is how to lookup for env variable inside chart by looking at the env variables it-self and not by passing this with --set.
for example: i have set a key "my_db_password" and want to change the values by looking at the value in env variable is not supported.
I am not very sure on GO template, but I guess this is disabled as what they explain in helm documentation. "We removed two for security reasons: env and expandenv (which would have given chart authors access to Tiller’s environment)." https://helm.sh/docs/developing_charts/#know-your-template-functions

Answer 7

I think one simple way is just set the value directly. for example, in your Values.yml, you want pass the service name:
...
myapp:
service:
name: ""
...
Your service.yml just use this value as usual:
{{ .Values.myapp.service.name }}
Then to set the value, use --set, like: --set myapp.service.name=hello
Then, for example, if you want to use the environment variable, do export before that:
#set your env variable
export MYAPP_SERVICE=hello
#pass it to helm
helm install myapp --set myapp.service.name=$MYAPP_SERVICE.
If you do debug like:
helm install myapp --set myapp.service.name=$MYAPP_SERVICE --debug --dry-run ./myapp
You can see this information at the beginning of your yml which your "hello" was set.
USER-SUPPLIED VALUES:
myapp:
service:
name: hello

Answer 8

As an alternative to pass local environment variables, I like to store these kind of sensitive values in a folder ignored by your VCS, and use Helm .Files object to read them and provide the values to your templates.
In my opinion, the advantage is that it doesn't require the host that will operate the Helm chart to set any OS specific environment variable, and makes the chart self-contained whilst not exposing these values.
# In a folder not committed, e.g. <chart_base_directory>/secrets
username: app-username
password: 28sin47dsk9ik
Then in your chart templates:
# In deployment.yaml file
---
apiVersion: v1
kind: Secret
metadata:
name: {{ .Release.Name }}-auth
stringData::
{{ .Files.Get "<chart_base_directory>/secrets" | indent 2 }}
As a result, everything the Chart needs is accessible from within the directory where you define everything else. And instead of setting system-wide env vars, it just needs a file.
This file can be generated automatically, or copied from a committed template with dummy values. Helm will also fire an error early on install/update if this isn't defined, as opposed to creating your secret with username="" and password="" if your env vars haven't been defined, which only becomes obvious once your changes are applied to the cluster.