Helm Charts

Package and deploy Kubernetes applications using Helm, the package manager for Kubernetes.

When to Use This Skill

Use this skill when:

Creating reusable Kubernetes application packages
Deploying applications with configurable values
Managing Helm releases and upgrades
Using third-party Helm charts
Implementing chart versioning and repositories

Prerequisites

Helm 3.x installed
kubectl configured with cluster access
Basic Kubernetes knowledge

Chart Structure

mychart/
├── Chart.yaml          # Chart metadata
├── values.yaml         # Default configuration values
├── charts/             # Chart dependencies
├── templates/          # Kubernetes manifest templates
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── secret.yaml
│   ├── _helpers.tpl    # Template helpers
│   ├── NOTES.txt       # Post-install notes
│   └── tests/
│       └── test-connection.yaml
└── .helmignore         # Files to ignore

Chart.yaml

apiVersion: v2
name: myapp
description: A Helm chart for MyApp
type: application
version: 1.0.0
appVersion: "2.0.0"
keywords:
  - myapp
  - web
maintainers:
  - name: DevOps Team
    email: devops@example.com
dependencies:
  - name: postgresql
    version: "12.x.x"
    repository: "https://charts.bitnami.com/bitnami"
    condition: postgresql.enabled

values.yaml

replicaCount: 2

image:
  repository: myapp
  tag: ""  # Defaults to appVersion
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: false
  className: nginx
  hosts:
    - host: myapp.example.com
      paths:
        - path: /
          pathType: Prefix
  tls: []

resources:
  limits:
    cpu: 500m
    memory: 256Mi
  requests:
    cpu: 100m
    memory: 128Mi

postgresql:
  enabled: true
  auth:
    database: myapp

Templates

Deployment Template

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      {{- include "myapp.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "myapp.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: 8080
          {{- with .Values.resources }}
          resources:
            {{- toYaml . | nindent 12 }}
          {{- end }}
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: {{ include "myapp.fullname" . }}-secrets
                  key: database-url

Helper Functions

# templates/_helpers.tpl
{{/*
Expand the name of the chart.
*/}}
{{- define "myapp.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

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

{{/*
Common labels
*/}}
{{- define "myapp.labels" -}}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
{{ include "myapp.selectorLabels" . }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

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

Conditional Resources

# templates/ingress.yaml
{{- if .Values.ingress.enabled -}}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
  {{- with .Values.ingress.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
spec:
  ingressClassName: {{ .Values.ingress.className }}
  {{- if .Values.ingress.tls }}
  tls:
    {{- range .Values.ingress.tls }}
    - hosts:
        {{- range .hosts }}
        - {{ . | quote }}
        {{- end }}
      secretName: {{ .secretName }}
    {{- end }}
  {{- end }}
  rules:
    {{- range .Values.ingress.hosts }}
    - host: {{ .host | quote }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ .path }}
            pathType: {{ .pathType }}
            backend:
              service:
                name: {{ include "myapp.fullname" $ }}
                port:
                  number: {{ $.Values.service.port }}
          {{- end }}
    {{- end }}
{{- end }}

Helm Commands

Installing Charts

# Install from local chart
helm install myapp ./mychart

# Install with custom values
helm install myapp ./mychart -f custom-values.yaml

# Install with value overrides
helm install myapp ./mychart \
  --set replicaCount=3 \
  --set image.tag=2.0.0

# Install in specific namespace
helm install myapp ./mychart -n production --create-namespace

# Dry run to preview
helm install myapp ./mychart --dry-run --debug

Managing Releases

# List releases
helm list
helm list -A  # All namespaces

# Upgrade release
helm upgrade myapp ./mychart
helm upgrade myapp ./mychart -f new-values.yaml

# Rollback
helm rollback myapp 1
helm history myapp

# Uninstall
helm uninstall myapp

Chart Development

# Create new chart
helm create mychart

# Lint chart
helm lint ./mychart

# Template locally (debug)
helm template myapp ./mychart

# Package chart
helm package ./mychart

# Update dependencies
helm dependency update ./mychart

Repositories

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

# Update repositories
helm repo update

# Search charts
helm search repo postgresql
helm search hub prometheus

# Install from repo
helm install postgres bitnami/postgresql

# Show chart info
helm show values bitnami/postgresql

Advanced Features

Hooks

# templates/pre-install-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: {{ include "myapp.fullname" . }}-migration
  annotations:
    "helm.sh/hook": pre-install,pre-upgrade
    "helm.sh/hook-weight": "-5"
    "helm.sh/hook-delete-policy": hook-succeeded
spec:
  template:
    spec:
      containers:
      - name: migrate
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        command: ["./migrate.sh"]
      restartPolicy: Never

Tests

# templates/tests/test-connection.yaml
apiVersion: v1
kind: Pod
metadata:
  name: "{{ include "myapp.fullname" . }}-test-connection"
  annotations:
    "helm.sh/hook": test
spec:
  containers:
    - name: wget
      image: busybox
      command: ['wget']
      args: ['{{ include "myapp.fullname" . }}:{{ .Values.service.port }}']
  restartPolicy: Never

# Run tests
helm test myapp

Library Charts

# Chart.yaml
apiVersion: v2
name: mylib
type: library
version: 1.0.0

# Using library chart
dependencies:
  - name: mylib
    version: "1.x.x"
    repository: "file://../mylib"

OCI Registry Support

# Login to registry
helm registry login registry.example.com

# Push chart to OCI registry
helm push mychart-1.0.0.tgz oci://registry.example.com/charts

# Pull from OCI registry
helm pull oci://registry.example.com/charts/mychart --version 1.0.0

# Install from OCI
helm install myapp oci://registry.example.com/charts/mychart

Common Issues

Issue: YAML Indentation Errors

Problem: Template renders with wrong indentation Solution: Use nindent helper function

{{- toYaml .Values.resources | nindent 12 }}

Issue: Values Not Applying

Problem: Custom values not reflected Solution: Check value paths, use --debug flag

helm template myapp ./mychart --debug

Issue: Dependency Errors

Problem: Chart dependencies not found Solution: Run helm dependency update

Issue: Release Already Exists

Problem: Cannot install, release exists Solution: Use helm upgrade --install

helm upgrade --install myapp ./mychart

Best Practices

Use semantic versioning for charts
Provide comprehensive default values
Document all values in values.yaml with comments
Use helper templates for repeated patterns
Implement chart tests
Use .helmignore to exclude unnecessary files
Pin dependency versions
Use helm lint in CI pipelines

Related Skills

kubernetes-ops - K8s fundamentals
argocd-gitops - GitOps with Helm
kustomize - Alternative templating

helm-charts