Mastering Helm Charts: Build a Fully Customizable Ghost Blog Deployment

Helm is easy to use, but creating a custom Chart package can be challenging due to Go template syntax. This guide walks through building a full Helm Chart for the Ghost blog application, a Node.js‑based open‑source platform.

Application

Ghost can be started with a simple Docker command, then accessed at http://localhost:2368. To run two replicas in a Kubernetes cluster, apply the following resource manifests:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ghost
spec:
  selector:
    matchLabels:
      app: ghost-app
  replicas: 2
  template:
    metadata:
      labels:
        app: ghost-app
    spec:
      containers:
      - name: ghost-app
        image: ghost
        ports:
        - containerPort: 2368

apiVersion: v1
kind: Service
metadata:
  name: ghost
spec:
  type: NodePort
  ports:
  - protocol: TCP
    targetPort: 2368
    port: 80

Apply them with kubectl apply -f ghost/deployment.yaml ghost/service.yaml and access Ghost via http://<nodeip>:31950.

Basic Template

Create a new chart with helm create my-ghost. Remove unused scaffold files and edit templates/deployment.yaml to use values such as {{ .Values.replicaCount }} for replicas and environment variables for configuration.

Naming Templates

Use the generated _helpers.tpl to replace fixed resource names with the chart or release name, ensuring multiple installations in the same namespace are possible.

Version Compatibility

Kubernetes version changes affect Ingress API versions. The guide shows how to detect the cluster version with .Capabilities.APIVersions.Has and render the appropriate Ingress manifest for networking.k8s.io/v1, v1beta1, or extensions/v1beta1.

Ingress

Add an Ingress template that adapts to the detected API version, uses ingressClassName for stable versions or the kubernetes.io/ingress.class annotation for older ones, and conditionally includes pathType when supported.

Persistence

Enable data persistence with a PVC. The chart conditionally creates a PersistentVolumeClaim when persistence.enabled is true, otherwise uses emptyDir. Values control storage class, access mode, and size.

Customization

Additional customizations include update strategies, node selectors, affinity, tolerations, resource limits, and optional liveness, readiness, and startup probes, all driven by values and rendered with toYaml for proper indentation.

Sharing Charts

Package the chart with helm package, host the .tgz and an index.yaml on GitHub Pages, and add the repository with helm repo add helm101 https://cnych.github.io/helm101/. Users can then search and install the chart via Helm.