Helm: The Package Manager

Deploying a single Pod is easy. Deploying a production application - which needs a Deployment, Service, Ingress, ConfigMap, Secret, and HPA - is hard.

Managing that same application across Dev, Staging, and Production (with different replica counts and image tags for each) is a nightmare.

Helm solves this. It is the "apt-get" or "npm" for Kubernetes. It allows you to bundle related YAML files into a single package called a Chart.

Think of your Kubernetes YAML files as "Cookies."

  • Without Helm: You hand-craft every single cookie (YAML file). If you need 10 cookies, you write 10 files. If you want to change the flavor, you edit 10 files.
  • With Helm: You create a Mold (Template).
    • You pour "dough" (Configuration Values) into the mold.
    • Helm presses the button and generates perfect YAML files for you every time.

Core Concepts

Term Definition
Chart The package itself. A directory containing templates and metadata. (The "Mold")
Values The configuration settings. (The "Dough"). Defined in values.yaml.
Release An instance of a Chart running in your cluster. (The "Cookie"). You can install the same chart 5 times to get 5 different releases.
Repository A place to store and share Charts (like Docker Hub, but for Helm).

Helm Architecture (v3+)

Forget Tiller. In the old days (Helm v2), there was a component called Tiller that ran inside your cluster with full admin rights. It was a massive security hole.

Helm v3 is client-only. When you run helm install, the Helm binary on your laptop:

  1. Reads your local charts/values.
  2. Generates the final YAML manifests.
  3. Talks directly to the Kubernetes API to apply them.
  4. Stores the "state" of the release in a Kubernetes Secret (in the same namespace).

The Directory Structure

When you run helm create my-chart, you get this standard layout:

my-chart/
  Chart.yaml          # Metadata (Name, Version, Dependencies)
  values.yaml         # Default configuration (The "Variables")
  charts/             # Sub-charts (Dependencies go here)
  templates/          # The Logic
    deployment.yaml   # A Deployment, but with {{ placeholders }}
    service.yaml      # A Service, but with {{ placeholders }}
    _helpers.tpl      # Reusable code snippets

The Templating Engine

Helm uses the Go Templating language. This is what makes it powerful.

1. The Template (templates/deployment.yaml) Instead of hardcoding "nginx", you use a variable.

apiVersion: apps/v1
kind: Deployment
spec:
  replicas: {{ .Values.replicaCount }}
  containers:
    - name: my-app
      image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"

2. The Values (values.yaml) You define the defaults here.

replicaCount: 3
image:
  repository: nginx
  tag: 1.21

3. The Result (Rendered Manifest) Helm combines them to create valid Kubernetes YAML.

apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 3
  containers:
    - name: my-app
      image: "nginx:1.21"

Daily Commands (Cheat Sheet)

1. Installation

Install a chart from a repo (like Bitnami).

helm repo add bitnami https://charts.bitnami.com/bitnami
helm install my-redis bitnami/redis

2. Customizing Values

You almost never use the default values. You override them.

# Option A: Command line flags (good for quick tests)
helm install my-web ./my-chart --set replicaCount=5

# Option B: Custom values file (Best Practice)
helm install my-web ./my-chart -f values-prod.yaml

3. Upgrading (Day 2 Operations)

Changed a value? Just run upgrade. Helm calculates the "diff" and patches the resources.

helm upgrade my-web ./my-chart -f values-prod.yaml

4. Rollbacks (The "Undo" Button)

Did your upgrade break production? Helm keeps a history of every release.

helm history my-web
# REVISION    UPDATED     STATUS      CHART
# 1           ...         SUPERSEDED  my-chart-1.0
# 2           ...         DEPLOYED    my-chart-1.1

# Rollback to revision 1 immediately
helm rollback my-web 1

Managing Dependencies

In Helm v3, you declare dependencies in Chart.yaml (not requirements.yaml).

# Chart.yaml
dependencies:
  - name: postgresql
    version: 10.x.x
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled

Then run:

helm dependency build

This downloads the postgres chart into your charts/ folder automatically.

Summary

  • Helm is the standard for packaging Kubernetes apps.
  • It separates Configuration (values.yaml) from Code (templates/).
  • It handles Dependencies (installing a database alongside your app).
  • It provides Revision History and Rollbacks out of the box.
  • Pro Tip: Always use --dry-run --debug before installing a complex chart to see exactly what YAML will be generated without actually applying it.