19 - Helm & Package Management

What Is Helm?

Helm is the package manager for Kubernetes (like apt for Ubuntu or brew for macOS). It lets you:

• Package multiple K8s resources into a single "chart"
• Template manifests with configurable values
• Manage releases (install, upgrade, rollback)
• Share charts via repositories

Key Concepts

Chart Structure

my-app/
├── Chart.yaml          # Chart metadata (name, version, dependencies)
├── values.yaml         # Default configuration values
├── charts/             # Dependencies (sub-charts)
├── templates/          # Kubernetes manifest templates
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── _helpers.tpl    # Template helpers
│   ├── NOTES.txt       # Post-install instructions
│   └── tests/
│       └── test-connection.yaml
├── .helmignore         # Files to exclude
└── README.md

Chart.yaml

yaml
apiVersion: v2
name: my-app
description: My web application
type: application    # or "library"
version: 1.2.0       # Chart version (SemVer)
appVersion: "3.1.0"  # App version
dependencies:
  - name: postgresql
    version: "13.x.x"
    repository: "https://charts.bitnami.com/bitnami"
    condition: postgresql.enabled

values.yaml

yaml
# Default values that users can override
replicaCount: 3

image:
  repository: myapp
  tag: "v3.1.0"
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: true
  className: nginx
  hosts:
    - host: app.example.com
      paths:
        - path: /
          pathType: Prefix
  tls:
    - secretName: app-tls
      hosts:
        - app.example.com

resources:
  requests:
    cpu: 250m
    memory: 256Mi
  limits:
    cpu: 500m
    memory: 512Mi

postgresql:
  enabled: true
  auth:
    database: myapp

Template Example

yaml
# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "my-app.fullname" . }}
  labels:
    {{- include "my-app.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      {{- include "my-app.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "my-app.selectorLabels" . | nindent 8 }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - containerPort: 8080
          {{- with .Values.resources }}
          resources:
            {{- toYaml . | nindent 12 }}
          {{- end }}

Helm Commands

Repository Management

bash
# Add a chart repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx

# Update repos
helm repo update

# Search for charts
helm search repo nginx
helm search hub wordpress    # Search Artifact Hub

Installing Charts

bash
# Install a chart
helm install my-release bitnami/nginx

# Install with custom values
helm install my-release bitnami/nginx -f custom-values.yaml

# Install with inline overrides
helm install my-release bitnami/nginx \
  --set replicaCount=3 \
  --set service.type=LoadBalancer

# Install in specific namespace
helm install my-release bitnami/nginx -n production --create-namespace

# Dry run (see what would be created)
helm install my-release bitnami/nginx --dry-run --debug

# Template only (render manifests without installing)
helm template my-release bitnami/nginx -f values.yaml

Managing Releases

bash
# List installed releases
helm list
helm list -n production
helm list --all-namespaces

# Get release info
helm status my-release
helm get values my-release        # Deployed values
helm get manifest my-release      # Deployed manifests
helm history my-release           # Revision history

# Upgrade a release
helm upgrade my-release bitnami/nginx -f new-values.yaml
helm upgrade --install my-release bitnami/nginx  # Install if doesn't exist

# Rollback
helm rollback my-release 1        # Rollback to revision 1
helm rollback my-release          # Rollback to previous

# Uninstall
helm uninstall my-release
helm uninstall my-release --keep-history  # Keep history for rollback

Creating Charts

bash
# Create a new chart scaffold
helm create my-app

# Lint (check for errors)
helm lint my-app/

# Package for distribution
helm package my-app/
# Creates my-app-1.2.0.tgz

# Push to OCI registry
helm push my-app-1.2.0.tgz oci://ghcr.io/myorg/charts

Helm Template Syntax (Go Templates)

yaml
# Variables
{{ .Values.image.tag }}
{{ .Release.Name }}
{{ .Chart.AppVersion }}

# Conditionals
{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
...
{{- end }}

# Loops
{{- range .Values.ingress.hosts }}
- host: {{ .host }}
{{- end }}

# Default values
{{ .Values.image.tag | default "latest" }}

# Pipelines
{{ .Values.name | upper | quote }}

# Include template helpers
{{ include "my-app.fullname" . }}

# toYaml (convert values to YAML)
{{- toYaml .Values.resources | nindent 12 }}

# With (set context)
{{- with .Values.nodeSelector }}
nodeSelector:
  {{- toYaml . | nindent 8 }}
{{- end }}

Alternatives to Helm

Kustomize (Built into kubectl)

bash
# Base
base/
├── kustomization.yaml
├── deployment.yaml
└── service.yaml

# Overlay (per environment)
overlays/
├── dev/
│   └── kustomization.yaml    # patches for dev
├── staging/
│   └── kustomization.yaml
└── production/
    └── kustomization.yaml

yaml
# overlays/production/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../base
namePrefix: prod-
patches:
  - patch: |-
      - op: replace
        path: /spec/replicas
        value: 5
    target:
      kind: Deployment
      name: web-app

bash
kubectl apply -k overlays/production/

FAANG Interview Angle

Common questions:

1. "What is Helm and why would you use it?"
2. "How do you manage different environments with Helm?"
3. "Compare Helm vs Kustomize"
4. "How do you handle secrets in Helm charts?"
5. "How do you rollback a Helm release?"

Key answers:

• Helm packages K8s manifests into reusable charts with templating and versioning
• Multiple values files (values-dev.yaml, values-prod.yaml) or --set overrides
• Helm: templates with Go syntax, good for distributing apps. Kustomize: patches, good for env overlays
• helm-secrets plugin, SOPS encryption, or reference external secrets by name
• helm rollback <release> <revision> -- Helm keeps history of all releases

Official Links

• Helm Documentation
• Artifact Hub (chart registry)
• Chart Best Practices
• Helm Template Guide
• Kustomize

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