Alright, let's walk through how to bring your existing Kubernetes application under Helm management—since you're already accessing the app via a Rancher-managed namespace, this process should fit right into your setup. Here's a step-by-step guide tailored to your scenario:

Step 1: Create a Base Helm Chart #

First, you need a Helm chart to act as the management template for your app. Start by generating a blank chart structure:

helm create my-app-chart

Navigate into the new my-app-chart directory. You'll notice a templates folder (where resource definitions live) and a values.yaml file (for configurable parameters). We'll use these to mirror your existing app's setup.

Step 2: Align the Chart with Your Existing App Resources #

Since your app is already running in the cluster, you need to make sure the Helm chart's definitions match your current resources exactly—this prevents Helm from creating duplicate resources or making unintended changes.

• First, export all your app's existing resources to a local file for reference:

  kubectl get all -n <your-rancher-namespace> -o yaml > existing-app-resources.yaml
  

• Split these resources into individual YAML files in the my-app-chart/templates directory (e.g., deployment.yaml, service.yaml, ingress.yaml).
• Replace hardcoded values (like image tags, resource limits) with Helm template variables. For example, change my-app-image:v2.3 to {{ .Values.image.repository }}:{{ .Values.image.tag }}, then define those values in values.yaml:

  image:
    repository: my-app-image
    tag: v2.3
  

This makes future updates (like version bumps) much easier.

Step 3: Dry Run to Validate the Chart #

Before you let Helm take over, run a dry run to confirm the resources Helm generates match your existing app perfectly:

helm install my-app-release ./my-app-chart --namespace <your-rancher-namespace> --dry-run --debug

Check the output YAML—you'll see Helm adds standard labels (like app.kubernetes.io/name) which are safe, but ensure all other configurations match your existing resources exactly.

Step 4: Let Helm Take Over Your Existing App #

Now you can officially register your existing app as a Helm release. Use the helm install command, and Helm will recognize the existing resources as part of this release:

helm install my-app-release ./my-app-chart --namespace <your-rancher-namespace>

If your namespace isn't already created (though you said you can access it via Rancher, so it should be), add --create-namespace to the command.

Verify the release was created successfully:

helm list -n <your-rancher-namespace>

You should see my-app-release listed. Use helm get all my-app-release -n <your-rancher-namespace> to confirm all your app's resources are now tracked by Helm.

Step 5: Test Helm Management Workflows #

Now that Helm is managing your app, try out common operations to ensure everything works:

• Check release status: helm status my-app-release -n <your-rancher-namespace>
• Upgrade the app (e.g., update the image tag in values.yaml):

  helm upgrade my-app-release ./my-app-chart -n <your-rancher-namespace>
  

• Roll back to a previous version:

  helm rollback my-app-release <revision-number> -n <your-rancher-namespace>
  

  (Get revision numbers with helm history my-app-release -n <your-rancher-namespace>)

Key Notes to Keep in Mind #

• Avoid making direct changes to your app's resources via kubectl or Rancher now—all updates should go through Helm to keep the release state consistent.
• If your app uses ConfigMaps or Secrets, add those to the templates directory too, or generate them via values.yaml for better management.
• Rancher's namespace permissions will apply to Helm operations as well—since you can run kubectl get pods in the namespace, Helm will have the same access.

内容的提问来源于stack exchange，提问作者Rajesh