Helm

Package manager for Kubernetes that helps you manage Kubernetes applications.

Basic Commands

COMMAND	DESCRIPTION
helm search repo <keyword>	Search for charts
helm repo add <name> <url>	Add chart repository
helm repo list	List repositories
helm repo update	Update repositories
helm install <release> <chart>	Install a chart
helm upgrade <release> <chart>	Upgrade a release
helm uninstall <release>	Uninstall a release
helm list	List releases

Release Management

COMMAND	DESCRIPTION
helm status <release>	Show release status
helm history <release>	Show release history
helm rollback <release> <revision>	Rollback to revision
helm get values <release>	Show release values
helm get manifest <release>	Show Kubernetes manifests
helm get all <release>	Show all information
helm ls --all-namespaces	List all releases

Chart Development

COMMAND	DESCRIPTION
helm create <name>	Create a new chart
helm lint <chart>	Lint a chart
helm package <chart>	Package a chart
helm dependency update	Update chart dependencies
helm template <release> <chart>	Render templates locally

Values & Configuration

COMMAND	DESCRIPTION
helm install -f values.yaml <release> <chart>	Install with custom values
helm install --set key=value <release> <chart>	Set individual values
helm install --set-file key=path <release> <chart>	Set values from file
helm show values <chart>	Show default values

Useful Flags

FLAG	DESCRIPTION
-n <namespace>	Specify namespace
--create-namespace	Create namespace if needed
--dry-run	Simulate install without making changes
--debug	Enable verbose output
--wait	Wait until resources are ready
--timeout 5m	Set timeout duration
--version <version>	Install specific chart version

Chart Structure

mychart/
├── Chart.yaml          # Chart metadata
├── values.yaml         # Default values
├── values.schema.json  # Values schema
├── charts/             # Chart dependencies
├── templates/          # Template files
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── _helpers.tpl    # Template helpers
│   └── NOTES.txt       # Usage notes
└── README.md           # Chart documentation

Chart.yaml

apiVersion: v2
name: mychart
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"

keywords:
  - mychart
  - kubernetes

maintainers:
  - name: Your Name
    email: your@email.com

dependencies:
  - name: postgresql
    version: 10.x.x
    repository: https://charts.bitnami.com/bitnami

Template Functions

Basic Functions

{{ .Values.replicaCount }}
{{ .Release.Name }}
{{ .Chart.Name }}
{{ .Values.image.repository }}:{{ .Values.image.tag }}

Conditionals

{{- if .Values.enabled }}
# Only rendered if enabled is true
{{- end }}

{{- if ne .Values.service.type "LoadBalancer" }}
# Only if service type is NOT LoadBalancer
{{- end }}

{{- if or .Values.featureA .Values.featureB }}
# If featureA OR featureB is true
{{- end }}

Loops

{{- range .Values.list }}
- name: {{ .name }}
  port: {{ .port }}
{{- end }}

{{- range $key, $value := .Values.dict }}
{{ $key }}: {{ $value }}
{{- end }}

Default Values

image: {{ .Values.image.repository | default "nginx" }}

String Manipulation

# Upper case
{{ "hello" | upper }}

# Lower case
{{ "HELLO" | lower }}

# Title case
{{ "hello world" | title }}

# Trim
{{ "  hello  " | trim }}

# Quote
{{ "hello" | quote }}

Common Templates

Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "mychart.fullname" . }}
  labels:
    {{- include "mychart.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      {{- include "mychart.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "mychart.selectorLabels" . | nindent 8 }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: {{ .Values.service.port }}
              protocol: TCP

Service

apiVersion: v1
kind: Service
metadata:
  name: {{ include "mychart.fullname" . }}
  labels:
    {{- include "mychart.labels" . | nindent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    {{- include "mychart.selectorLabels" . | nindent 4 }}

ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ include "mychart.fullname" . }}-config
  labels:
    {{- include "mychart.labels" . | nindent 4 }}
data:
  {{- toYaml .Values.config | nindent 2 }}

Secret

apiVersion: v1
kind: Secret
metadata:
  name: {{ include "mychart.fullname" . }}-secret
  labels:
    {{- include "mychart.labels" . | nindent 4 }}
type: Opaque
data:
  password: {{ .Values.secret.password | b64enc }}

Helper Functions

Common helpers.tpl

{{/*
Expand the name of the chart.
*/}}
{{- define "mychart.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create chart name and version as used by the chart label.
*/}}
{{- define "mychart.chart" -}}
{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create default fully qualified app name.
*/}}
{{- define "mychart.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- if contains $name .Release.Name }}
{{- .Release.Name | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}
{{- end }}

{{/*
Create chart name and version.
*/}}
{{- define "mychart.labels" -}}
helm.sh/chart: {{ include "mychart.chart" . }}
{{ include "mychart.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{/*
Selector labels
*/}}
{{- define "mychart.selectorLabels" -}}
app.kubernetes.io/name: {{ include "mychart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

Examples

Install with custom values

helm install myapp ./mychart -f values-prod.yaml

Install from repository

helm install myapp bitnami/nginx --set service.type=LoadBalancer

Upgrade a release

helm upgrade myapp ./mychart -f values.yaml

Rollback

helm rollback myapp 1

Template rendering (dry-run)

helm template myapp ./mychart -f values.yaml

Show chart info

helm show chart bitnami/nginx
helm show values bitnami/nginx
helm show readme bitnami/nginx

Best Practices

• Use semantic versioning for charts
• Document all values in README
• Use values.schema.json for validation
• Include NOTES.txt for post-install instructions
• Use helper functions for common labels and names
• Keep templates simple and readable
• Use proper indentation
• Add comments for complex logic
• Test charts with helm lint and helm template
• Use dependencies instead of copying code
• Follow Kubernetes best practices

TIP

Use helm diff upgrade <release> <chart> to preview changes before upgrading (requires helm-diff plugin).