Helm

Introduction

Helm is the package manager for Kubernetes. It streamlines installing and managing Kubernetes applications by packaging related resources into charts — versioned, shareable bundles of pre-configured Kubernetes resource definitions.

Key Concepts

• Chart — A Helm package containing all resource definitions necessary to run an application, tool, or service inside a Kubernetes cluster.
• Repository — A place where charts can be collected and shared (e.g., ArtifactHub).
• Release — An instance of a chart running in a Kubernetes cluster. One chart can be installed many times, each creating a new release.
• Values — Configuration that can be overridden at install/upgrade time to customize a chart's behavior.

Architecture

Helm 3 uses a client-only architecture (no Tiller). The Helm client interacts directly with the Kubernetes API server and stores release metadata as Secrets or ConfigMaps in the target namespace.

┌──────────┐     ┌────────────────┐     ┌──────────────┐
│ Helm CLI │────▶│ Kubernetes API │────▶│ etcd (state) │
└──────────┘     └────────────────┘     └──────────────┘
      │
      ▼
┌──────────────┐
│ Chart Repos  │
│ / OCI Registry│
└──────────────┘

Common Operations

# Add a chart repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

# Search for charts
helm search repo nginx
helm search hub prometheus

# Install a chart
helm install my-release bitnami/nginx -n my-namespace --create-namespace

# Install with custom values
helm install my-release bitnami/nginx -f custom-values.yaml

# List releases
helm list -A

# Upgrade a release
helm upgrade my-release bitnami/nginx --set replicaCount=3

# Rollback to a previous revision
helm rollback my-release 1

# Uninstall a release
helm uninstall my-release -n my-namespace

# Template rendering (dry-run)
helm template my-release bitnami/nginx -f values.yaml

Chart Development

# Create a new chart scaffold
helm create my-chart

# Lint a chart for issues
helm lint my-chart/

# Package a chart for distribution
helm package my-chart/

# Push to OCI registry
helm push my-chart-0.1.0.tgz oci://registry.example.com/charts

Chart Structure

my-chart/
├── Chart.yaml          # Chart metadata (name, version, dependencies)
├── values.yaml         # Default configuration values
├── charts/             # Dependency charts
├── templates/          # Kubernetes manifest templates
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── _helpers.tpl    # Template helpers / named templates
│   └── NOTES.txt       # Post-install usage notes
└── .helmignore         # Patterns to ignore when packaging

CLI Reference

Reference:

1. Official Website
2. Repository
3. ArtifactHub