Advanced Helm Charts- How to create the Templates

4 min readJul 5, 2021

Topics to be covered

Built In Objects
Read values for Template
Set Values to Template
Template functions
Template Pipelines and Control flow if Else

How to create Helm Charts

helm create mychart ( it will create a new chart)

rm -rf mychart/templates* (for removing the default template)

Now we will learn to create the helm charts, updating the templates. And we will also learn how to install and uninstall the chart.

Under Templates create a configmap.yaml as below:

apiVersion: v1
kind: ConfigMap
metadata:
name: mychart-configmap
data:
myvalue: “Sample Config Map”

helm install helm-demo-configmap ./mychart (for installing the helm charts)

helm uninstall helm-demo-configmap (for uninstalling the helm charts)

Built In Objects

Now we are going to introduce the template using double flower brackets. We can also pass the values in values.yaml but we have some builtin objects.

Ref Link: Click Here

apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name}}-configmap
data:
myvalue: “Sample Config Map”

helm install releasename-test ./mychart (for installing the chart using .Release.Name as defined above)

helm get manifest releasename-test (use to list the charts)

Note: The derivative is replaced with the name which we have given(releasename-test) . Above is the template derivative(.Release.Name) example using the built in objects.

Read values for Template

Now we will learn how to use our own values

Remove the default field’s values in value.yaml and add your own. And it will substitute the new values in the configmap.yaml

In values.yaml we pass this value cat mychart/values.yaml

costCode: CC6721

helm install — debug — dry-run firstdryrun ./mychart (we are using dryrun so that it will just reflect the changes instead of applying)

Till now we have learned how to read values from templates. Also we got to know how to use dry run.

Set Values to Template

In the below example we have replaced the costcode with some other value. As set is having the more precedence so it will replace the value in configmap.yaml

helm install — dry-run — debug — set costCode=00000 valueteg ./mychart/

We can use this when we want to use the custom value for a specific release.

Template functions

Function plays a very important role which dynamically changes the values

apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name}}-configmap
data:
myvalue: “Sample Config Map”
costCode: {{ .Values.costCode }}
Zone: {{ quote .Values.infra.zone }}
Region: {{ quote .Values.infra.region }}
ProjectCode: {{ upper .Values.projectCode }}

In which upper is used to convert the values from lower to upper and quote is used to add the quotes

Here is the Reference Link : Click Here

Here are the values for the above template: cat mychart/values.yaml

costCode: CC6721
projectCode: aacbbff
infra:
zone: a,b,c
region: us-e

helm install — dry-run — debug valuesteg ./mychart

Below is the output after applying the chart

Template Pipelines

apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name}}-configmap
data:
myvalue: “Sample Config Map”
costCode: {{ .Values.costCode }}
Zone: {{ quote .Values.infra.zone }}
Region: {{ quote .Values.infra.region }}
ProjectCode: {{ upper .Values.projectCode }}
pipeline: {{ .Values.projectCode | upper | quote }}
now: {{ now | date “2021–06–02” | quote }}
contact: {{ .Values.contact | default “1–1800–5665–890” | quote }}

In the now field, now is used for date we can use this in above format and in contact field, default pick those values which we pass in template if it is available or not in values.yaml

helm install — dry-run — debug valuesteg ./mychart

We have used the values.yaml from the Template functions in this case but will get some more info in our output