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Helm Chart Basics

Helm Repositories

By default, Helm does not come with pre-configured repositories. You must add them manually.

Add Stable Repo

helm repo add stable https://charts.helm.sh/stable

Chart Dependencies

Dependencies allow a chart to build upon other charts. They are defined in Chart.yaml and stored in the charts/ directory.

Defining Dependencies

In parentchart/Chart.yaml: 

apiVersion: v2
name: parentchart
version: 1.0.0
dependencies:
  - name: apache
    version: 1.2.3
    repository: https://example.com/charts
  - name: mysql
    version: 3.2.1
    repository: https://another.example.com/charts

Using Aliases

You can install the same chart multiple times with different names using alias. 

dependencies:
  - name: redis
    version: 1.0.0
    repository: https://charts.bitnami.com/bitnami
    alias: redis-cache
  - name: redis
    version: 1.0.0
    repository: https://charts.bitnami.com/bitnami
    alias: redis-queue

Tags and Conditions

You can control the installation of dependencies using tags and condition in Chart.yaml.

  • Condition: Values path (e.g., subchart.enabled). First valid path wins.
  • Tags: Group dependencies (e.g., front-end, back-end).

Priority: condition > tags.

# Chart.yaml
dependencies:
  - name: frontend
    condition: frontend.enabled
    tags:
      - web-tier

# Enable via CLI
helm install myapp . --set frontend.enabled=false

Passing Values to Subcharts

Global Values

The global key in values.yaml is accessible by all charts (parent and subcharts). 

global:
  app: MyWordPress

Subchart Values

Pass values to a specific subchart by using its name as a key. 

mysql:       # dependency name
  auth:
    rootPassword: secret

Value Validation (values.schema.json)

You can modify values.schema.json to enforce types and required fields for your values. 

{
  "$schema": "https://json-schema.org/draft-07/schema#",
  "required": ["image", "port"],
  "properties": {
    "port": { "type": "integer" },
    "image": { "type": "string" }
  }
}

Custom Resource Definitions (CRDs)

Helm has specific limitations for managing CRDs in the crds/ folder:

  1. Install Only: Helm installs them, but never upgrades or deletes them.
  2. Global Scope: Deleting a CRD wipes data across all namespaces, so Helm avoids touching them for safety.
  3. No Templating: Files in crds/ are plain YAML; templating is not supported.

🧠 Quick Quiz

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Which command installs a chart?

👉 Take the Helm Basics Quiz

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