Helm Intermediate Guide¶

Move beyond the basics and master the power of Helm's templating engine.

📝 Templating Engine¶

Helm uses the Go Template language. Templates are located in the templates/ directory and are combined with values.yaml to generate valid Kubernetes manifests.

The Scope (`.`)¶

The dot . represents the current context. In the top scope, it contains: * .Values (from values.yaml) * .Release (Name, Namespace, Service) * .Chart (Metadata from Chart.yaml) * .Capabilities (Kubernetes cluster versions)

apiVersion: v1
kind: Pod
metadata:
  name: {{ .Release.Name }}-app

🔄 Flow Control¶

If / Else¶

Control what gets rendered based on values.

{{- if .Values.ingress.enabled }}
kind: Ingress
metadata:
  name: example
{{- else }}
# Ingress is disabled
{{- end }}

Note: The - trims whitespace (newlines) before or after the bracket.

With¶

Changes the scope (.) to a specific object to avoid repetition.

{{- with .Values.image }}
image: {{ .repository }}:{{ .tag }}
{{- end }}

Range (Loops)¶

Iterate over lists or maps.

env:
{{- range .Values.env }}
  - name: {{ .name }}
    value: {{ .value }}
{{- end }}

⚓ Helm Hooks¶

Hooks allow you to intervene at specific points in a release's life cycle. Common use cases include: * pre-install/post-install: Run database migrations or seed data. * pre-delete: Clean up external resources.

Define a hook using an annotation:

apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-migrate"
  annotations:
    "helm.sh/hook": pre-install,pre-upgrade
    "helm.sh/hook-delete-policy": hook-succeeded

🛠️ Debugging Templates¶

Dry Run¶

Simulate an install and check for validation errors.

helm install myapp . --dry-run

Template Render¶

Print the raw generated YAML to stdout (useful for inspecting logic).

helm template myapp .

With debug info:

helm template myapp . --debug

📦 Named Templates (`_helpers.tpl`)¶

To reuse logic (like standard labels), define named templates in a file starting with _ (usually _helpers.tpl).

Definition:

{{/* _helpers.tpl */}}
{{- define "mychart.labels" -}}
app: {{ .Chart.Name }}
version: {{ .Chart.Version }}
managed-by: {{ .Release.Service }}
{{- end }}

Usage:

metadata:
  labels:
    {{- include "mychart.labels" . | nindent 4 }}

🧠 Quick Quiz¶

#

What templating engine does Helm use?

👉 Take the Helm Intermediate Quiz

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