Chart structure

Learn the Helm chart directory structure.

Chart structure

A chart is a specific folder layout. helm create produces a sample skeleton:

magaza/
  Chart.yaml          # name, version, description
  values.yaml         # default values
  templates/          # YAMLs with Go templates
    deployment.yaml
    service.yaml
    _helpers.tpl      # shared template pieces
    NOTES.txt         # post-install message
  charts/             # dependent charts

# Chart.yaml
apiVersion: v2
name: magaza
version: 0.1.0        # chart version
appVersion: "1.4.2"   # application version

Templates

The files under templates/ use the Go template language. {{ .Values.x }} reads from values.yaml, {{ .Release.Name }} from the release name, {{ .Chart.AppVersion }} from Chart.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-web
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
        - name: web
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"

Exercise A chart skeleton

Two steps: write the command creating a chart skeleton named magaza; then write the Chart.yaml contents: apiVersion: v2, name: magaza, version: 0.1.0, appVersion: "1.4.2".

Show example solution

helm create magaza

# Chart.yaml
apiVersion: v2
name: magaza
version: 0.1.0
appVersion: "1.4.2"

Test yourself

What is the difference between version and appVersion in Chart.yaml?
- appVersion is the Kubernetes version
- version is the Helm version
- version is the chart package's version, appVersion the application inside it
- They are the same
Show answer

version is the chart package's version, appVersion the application inside it — When the templates change, version goes up; when the image changes, appVersion.

Read the value from values.yaml.

  replicas: {{ .____.replicaCount }}

Show answer

  replicas: {{ .Values.replicaCount }}

Match.

Chart.yaml

Chart information
values.yaml

Default values
templates/

Templated YAML
.Release.Name

Release name

Next lesson: helm install

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