Helm charts are packages of pre-configured Kubernetes resources. They allow you to define, install, and upgrade even the most complex Kubernetes applications. This tutorial will guide you through the process of creating a basic Helm chart.

Prerequisites:

• Helm installed on your system.
• kubectl configured to connect to your Kubernetes cluster.

1. Setting up the Chart Structure

Use the helm create command to generate a basic chart structure:

helm create my-first-chart

This will create a directory named my-first-chart with the following structure:

my-first-chart/
├── charts/
├── templates/
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   └── service.yaml
├── Chart.yaml
└── values.yaml

• charts/: Contains chart dependencies (subcharts).
• templates/: Holds Kubernetes manifest templates.
• Chart.yaml: Contains metadata about the chart.
• values.yaml: Defines default values for the templates.

2. Understanding Chart.yaml

Open my-first-chart/Chart.yaml and examine its contents:

apiVersion: v2
name: my-first-chart
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"

• apiVersion: The API version of the chart.
• name: The name of the chart.
• description: A brief description of the chart.
• type: The type of the chart (application or library).
• version: The chart’s version.
• appVersion: The version of the application being deployed.

Modify these values as needed for your application.

3. Modifying values.yaml

Open my-first-chart/values.yaml and add or modify values as required. For example:

replicaCount: 1
image:
  repository: nginx
  pullPolicy: IfNotPresent
  tag: "1.16.0"
service:
  type: ClusterIP
  port: 80

These values will be used to populate the templates in the templates/ directory.

4. Editing the Deployment Template

Open my-first-chart/templates/deployment.yaml and modify it to match your application’s requirements. For example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-deployment
  labels:
    app: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Release.Name }}
  template:
    metadata:
      labels:
        app: {{ .Release.Name }}
    spec:
      containers:
      - name: {{ .Release.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        imagePullPolicy: {{ .Values.image.pullPolicy }}
        ports:
        - containerPort: {{ .Values.service.port }}

• {{ .Release.Name }}: Accesses the release name.
• {{ .Values.replicaCount }}: Accesses the replicaCount value from values.yaml.
• {{ .Values.image.repository }}: Accesses the image.repository value.
• {{ .Values.image.tag }}: Accesses the image.tag value.
• {{ .Values.image.pullPolicy }}: access the pull policy of the image.
• {{ .Values.service.port }}: Accesses the service port.

5. Editing the Service Template

Open my-first-chart/templates/service.yaml and modify it:

apiVersion: v1
kind: Service
metadata:
  name: {{ .Release.Name }}-service
  labels:
    app: {{ .Release.Name }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: {{ .Values.service.port }}
      protocol: TCP
  selector:
    app: {{ .Release.Name }}

6. Installing the Chart

Navigate to the chart’s directory:

cd my-first-chart

Install the chart:

helm install my-release .

• my-release: The release name.
• .: The current directory (where the chart is located).

Verify the deployment:

kubectl get deployments
kubectl get services

7. Upgrading the Chart

• Modify values.yaml or templates/ as needed.
• Upgrade the release:

helm upgrade my-release .

Verify the changes:

kubectl get deployments

8. Packaging the Chart

Package the chart:

helm package .

This will create a .tgz file that can be distributed.

9. Installing a packaged chart

Install the packaged chart:

helm install my-release my-first-chart-0.1.0.tgz

10. Uninstalling the release

helm uninstall my-release