Helm Charts Anatomy

Introduction

Helm is a package manager for Kubernetes that helps you define, install, and manage Kubernetes applications. Helm uses a packaging format called charts. This lesson provides a detailed overview of Helm charts, their structure, and best practices for usage.

Key Concepts

• **Chart**: A collection of files that describe a related set of Kubernetes resources.
• **Release**: An instance of a chart running in a Kubernetes cluster.
• **Repository**: A place where charts are stored and shared.
• **Values**: Configuration values that modify chart behavior.

Chart Structure

A Helm chart has a specific directory structure. Below is an example of a simple chart structure:

mychart/
├── Chart.yaml
├── values.yaml
├── charts/
├── templates/
│   ├── deployment.yaml
│   └── service.yaml
            

Each component is explained as follows:

• Chart.yaml: Contains metadata about the chart (name, version, etc.).
• values.yaml: Default values for the templates in the chart.
• charts/: Directory for dependencies of the chart.
• templates/: Contains Kubernetes manifest files that will be rendered into valid YAML.

Templates

Templates are files that use the Go template language to allow for dynamic content. For example, a basic deployment template can look like this:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-nginx
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    metadata:
      labels:
        app: {{ .Release.Name }}-nginx
    spec:
      containers:
      - name: nginx
        image: "nginx:{{ .Values.image.tag }}"
            

Values.yaml

The values.yaml file allows users to configure their charts without modifying the templates. Here’s an example:

replicaCount: 2
image:
  repository: nginx
  tag: stable
            

Best Practices

• Keep your charts versioned and use semantic versioning.
• Document your charts and provide example values.
• Use templates wisely to minimize duplication.
• Test your charts regularly with `helm lint` and `helm install --dry-run`.

FAQ