Learn Helm

Learn how to use Helm to install any application on Kubernetes.

Install Helm

Install Helm client on your workstation

Every Helm release provides command line binary for any operating system. These versions can be manually downloaded and installed.

Get your desired latest version of Helm:

wget https://get.helm.sh/helm-v3.10.3-linux-amd64.tar.gz

Extract the tarball archive to your local filesystem:

tar -xvzf helm-v3.10.3-linux-amd64.tar.gz

Install helm client in /usr/local/bin:

sudo install -m 755 linux-amd64/helm /usr/local/bin/helm

Check helm command:

helm version

Output:

version.BuildInfo{Version:"v3.10.3", GitCommit:"835b7334cfe2e5e27870ab3ed4135f136eecc704", GitTreeState:"clean", GoVersion:"go1.18.9"}

As the last step add autocompletion bash functions to your shell:

helm completion bash
source <(helm completion bash)
echo "source <(helm completion bash)" >> ~/.bashrc

Generate Helm chart template

Helm can also be used for generating chart templates:

helm create example

Check the structure of the Helm chart package directory:

sudo apt-get install tree
tree example

Output:

example/
├── charts
├── Chart.yaml
├── templates
│   ├── deployment.yaml
│   ├── _helpers.tpl
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── NOTES.txt
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

3 directories, 10 files

note

To get more info about Helm Chart Templates you go to official documentation

Verify Helm lint for example package:

helm lint example/

Test example Helm Chart installation:

helm install --create-namespace --namespace test example ./example/ --dry-run --debug

See created Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example
  labels:
    helm.sh/chart: example-0.1.0
    app.kubernetes.io/name: example
    app.kubernetes.io/instance: example
    app.kubernetes.io/version: "1.16.0"
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: example
      app.kubernetes.io/instance: example
  template:
    metadata:
      labels:
        app.kubernetes.io/name: example
        app.kubernetes.io/instance: example
    spec:
      serviceAccountName: example
      securityContext:
        {}
      containers:
        - name: example
          securityContext:
            {}
          image: "nginx:1.16.0"
          imagePullPolicy: IfNotPresent
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
          livenessProbe:
            httpGet:
              path: /
              port: http
          readinessProbe:
            httpGet:
              path: /
              port: http
          resources:
            {}

Then we can try to install it on the Kubernetes cluster:

helm install --create-namespace --namespace test example ./example/

Verify the status of the example application on Kubernetes:

kubectl get deploy,rs,pods -n test
kubectl get svc -n test

Now we can check the example application release using Helm:

helm list -n test
helm status -n test example
helm history -n test example

Since the NGiNX image used in this example is outdated, let's upgrade the example app with a new image:

helm upgrade -n test example ./example/ --set image.tag="1.23.2"

Let's verify the application release once again:

helm list -n test
helm status -n test example
helm history -n test example

To check image version and status application we can use:

kubectl get deploy,rs,pods -n test -o wide

Develop simple Helm chart

Generate new Helm chart:

helm create myapp

Remove unnecessary files:

rm myapp/charts myapp/templates/* myapp/values.yaml -r

Go into myapp directory and edit Chart.yaml:

Chart.yaml

apiVersion: v2
name: myapp
description: A Helm chart for Kubernetes

type: application

version: 0.1.0

appVersion: "v1.0"

Go into the templates subdirectory and generate the deployment.yaml manifest:

cd templates
kubectl create deployment myapp --image=ghcr.io/mjura/myapp:v1.0 --replicas=3 --dry-run=client -o yaml > deployment.yaml

Edit deployment.yaml manifest:

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: myapp
  name: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - image: "{{ .Values.image }}:{{ .Chart.AppVersion }}"
        name: myapp

Go to main myapp directory:

cd ..

and create values.yaml:

values.yaml

replicaCount: 3

image: ghcr.io/mjura/myapp

Check the myapp Helm chart directory tree:

cd ..
tree myapp

Output:

myapp/
├── Chart.yaml
├── templates
│   └── deployment.yaml
└── values.yaml

Validate the myapp Helm chart:

helm lint ./myapp

Output:

==> Linting ./myapp/
[INFO] Chart.yaml: icon is recommended

1 chart(s) linted, 0 chart(s) failed

Try to generate and perform a dry run of the myapp installation:

helm install --create-namespace --namespace myapp release-name ./myapp --debug --dry-run

See created Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: myapp
  name: release-name
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - image: "ghcr.io/mjura/myapp:v1.0"
        name: myapp

To install myapp, just execute:

helm install --create-namespace --namespace myapp release-name ./myapp

Check the status of the application installation:

helm list -n myapp
helm status -n myapp release-name
helm history -n myapp release-name

Check the list of Deployments and Pods:

kubectl get deploy,rs,pods -n myapp
kubectl logs -n myapp -l app=myapp

Clean up:

kubectl delete ns test myapp