Helm Basics

Helm, the package manager for Kubernetes.⌗

Where ever we hear about application deployment in kubernetes, we hear about an addon, Helm. So what is this Helm? Why so much hype? And how to use that?

Introduction⌗

You can deploy application in kubernetes using yaml. For example, deployment, service, hpa. The list goes on and on. But when you’re sharing the template, for example, with one of your friend, he/she might need to customize the service type from LoadBalancer to NodePort. Or change the name from “Bob’s awsome app” to “Alice’s awsome app”. This task will be little daunting, if you have 100’s or even 10’s of services.

Helm is a templating format/engine for the kubernetes application, so that you can share the generic structure of the application to any one in a customizable manner.

Code⌗

Deploying Hello-World application using kubernetes yaml.

First let’s create an nginx deployment, which will create nginx deployment and a service type LoadBalancer

Note: if you don’t have kubernetes cluster, use k3d to create one. Refer here.

kubectl apply -f - << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
      - name: name
        image: rancher/hello-world
        resources:
          requests:
            cpu: 100m
            memory: 200Mi
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: hello-world
  namespace: default
spec:
  type: ClusterIP
  ports:
  - port: 80
    targetPort: 8
  selector:
    app: hello-world
EOF

Download Helm

Linux

 sudo su
 which helm &> /dev/null
 if [[ $? -ne 0 ]]; then
     echo "helm not installed. Installing it..."
     curl -ssl https://get.helm.sh/helm-v3.8.0-linux-amd64.tar.gz -o /tmp/helm.tar.gz
     tar -xf /tmp/helm.tar.gz
     chmod +x linux-amd64/helm
     sudo cp linux-amd64/helm /usr/local/bin/helm
     rm -rf linux-amd64/helm /tmp/helm.tar.gz
 fi
 exit

From Chocolatey (Windows)

choco install kubernetes-helm

From Homebrew (macOS)

brew install helm

Deploy Hello-World application using helm.
```
# Creating helm chart
helm create hello-world
```
```
# Installing helm chart
helm install my-hello-world --namespace default ./hello-world
```
But when you inspect the deployment, you’ll see the container image is nginx, rather than rancher/hello-world
```
kubectl describe deploment Hello-World
```
This is because when you did helm create hello-world, Helm created a template with some boilerplate code.

Structure of a helm chart.

❯ tree hello-world
hello-world
├── charts              # directory to put sub-charts
├── Chart.yaml          # Information about the chart
├── templates           # Folder containes the yaml's which will be templated
│   ├── deployment.yaml
│   ├── _helpers.tpl    # helm's helper function for advanced templating
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── NOTES.txt       # Information about the appiction usage
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests           # If you have any test cases for your application
│       └── test-connection.yaml
└── values.yaml         # File which we'll use to override the defaults

3 directories, 10 files

Customizing Helm chart for our application needs
```
# Customizing the boilerplate
vim values.yaml
```
Edit the following sections in values.yaml

Note: Yaml syntax is space sensitive. So make sure your spaces are proper.
```
# Changing the image from nginx to `rancher/hello-world`
image:
  repository: rancher/hello-world
```
Note: use :wq! for save and quit from vim
Upgrading our application with helm.
```
helm upgrade my-hello-world --namespace default
```
After the upgrade completes,
```
kubectl describe deploment Hello-World
```
Now you can see the rancher/hello-world image, not the default nginx image

Now, if you want, you can change the service.type from ClusterIP to LoadBalancer to expose the application, externally.

Happy Helming!!!