Master Helm: A Complete Guide to Kubernetes Package Management

Overview

Helm is the package manager for Kubernetes, similar to apt‑get/yum. Helm repositories contain only chart manifests; container images are provided by image registries such as Docker Hub.

Official documentation: https://v3.helm.sh/zh/docs/

Helm Architecture

Helm Installation

# Download package
wget https://get.helm.sh/helm-v3.9.4-linux-amd64.tar.gz
# Extract archive
tar -xf helm-v3.9.4-linux-amd64.tar.gz
# Create symlink
ln -s /opt/helm/linux-amd64/helm /usr/local/bin/helm
# Verify
helm version
helm help

Helm Components and Terminology

Helm

– client tool for creating, packaging, and managing charts. Chart – a Helm package containing all Kubernetes resources needed for an application. Release – an instance of a chart deployed in a cluster. Repository – a storage location for sharing charts.

Chart Structure

Directory Layout

# helm create nginx
tree nginx

nginx/
├── charts   # dependent charts
├── Chart.yaml   # chart metadata
├── templates/
│   ├── deployment.yaml
│   ├── _helpers.tpl
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── NOTES.txt
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests/
│       └── test-connection.yaml
└── values.yaml   # default values

Chart.yaml Fields

apiVersion: chart API version (required)
name: chart name (required)
version: semantic version (required)
kubeVersion: compatible Kubernetes version (optional)
description: one‑line description (optional)
type: chart type (optional)
keywords: list of keywords (optional)
home: project home URL (optional)
sources: list of source URLs (optional)
dependencies: list of required charts (optional)
maintainers: list of maintainers (optional)
icon: URL of an SVG or PNG icon (optional)
appVersion: version of the contained application (optional)
deprecated: boolean flag (optional)
annotations: custom metadata (optional)

Note: Starting with v3.3.2, additional fields are no longer allowed. Custom metadata should be added to annotations .

Dependencies

Dependencies are defined in the dependencies list of Chart.yaml. Example:

dependencies:
  - name: apache
    version: "1.2.3"
    repository: "https://example.com/charts"
    condition: subchart1.enabled
    tags:
      - front-end
    import-values:
      - data

Run helm dependency update to download the specified charts.

Templates and Values

Templates are written in Go templating language with Sprig functions and live in the templates/ directory. Values are supplied via values.yaml, additional -f files, or --set arguments.

Built‑in Objects

Release

– provides .Name, .Namespace, .IsInstall, .IsUpgrade, etc. Values – the merged values from all sources. Chart – metadata from Chart.yaml. Files – access to non‑ignored files in the chart. Capabilities – Kubernetes version and API capabilities.

Common Functions

Examples include quote, default, printf, trim, upper, lower, replace, date, and many type‑conversion and list functions.

Control Structures

Use if / else, with, and range for conditional rendering and loops. Example of a range over a list of pizza toppings:

toppings: |-
{{- range .Values.pizzaToppings }}
- {{ . | title | quote }}
{{- end }}

Named Templates

Define reusable snippets with {{ define "mychart.labels" }} … {{ end }} and include them via {{ template "mychart.labels" . }} or {{ include "mychart.labels" . | indent 4 }} to preserve indentation.

NOTES.txt

The templates/NOTES.txt file provides post‑install instructions to users. It is processed as a template but rendered as plain text.

Debugging

Useful commands: helm lint, helm install --dry-run --debug, helm template --debug, and helm get manifest. Comment out problematic sections and re‑run to isolate errors.

For the full reference, see the original article: https://www.cnblogs.com/liugp/p/16659802.html