Helm Basics by example

Installation and Verification

Its easier to understand the principles of helm by executing a simple example. Let’s search the web for a sample Who-am-i application that just responds with the requests headers

https://www.google.de/search?q=helm+chart+who-am-i

We are using one of the first matches and add the repo as suggested:

helm repo add halkeye https://halkeye.github.io/helm-charts/

Note that this is just a very simple chart. It just illustrates operations. We will see the major benefits when installing more complex charts later. The real power is helms templating solution which substitutes the charts placeholders with parameters during installation.

Before executing an installation its very easy to check what it will do.
Just replace helm install ... with helm template ...

Verify

Now lets evaluate the charts rendered templates before installation. No operation is performed, its just output of the manifests to be executed on install:

helm template whoami halkeye/whoami --version 0.3.2

Console output:

# Source: whoami/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: whoami
  labels:
    app.kubernetes.io/name: whoami
    helm.sh/chart: whoami-0.3.2
    app.kubernetes.io/instance: whoami
    app.kubernetes.io/version: "v1.4.0"
    app.kubernetes.io/managed-by: Helm
spec:
  type: ClusterIP
  ports:
    - port: 80
      targetPort: http
      protocol: TCP
      name: http
  selector:
    app.kubernetes.io/name: whoami
    app.kubernetes.io/instance: whoami
---
# Source: whoami/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: whoami
  labels:
    app.kubernetes.io/name: whoami
    helm.sh/chart: whoami-0.3.2
    app.kubernetes.io/instance: whoami
    app.kubernetes.io/version: "v1.4.0"
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: whoami
      app.kubernetes.io/instance: whoami
  template:
    metadata:
      labels:
        app.kubernetes.io/name: whoami
        app.kubernetes.io/instance: whoami
    spec:
      containers:
        - name: whoami
          image: "containous/whoami:v1.4.0"
          imagePullPolicy: IfNotPresent
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
          livenessProbe:
            httpGet:
              path: /health
              port: http
          readinessProbe:
            httpGet:
              path: /health
              port: http
          resources:
            {}

or pull the chart to a local folder for local analysis and modification

helm pull halkeye/whoami --version 0.3.2

Install

kubectl create namespace whoami
helm install whoami halkeye/whoami -n whoami --version 0.3.2

Installer responds with

NAME: whoami
LAST DEPLOYED: Tue Jul  7 10:57:26 2020
NAMESPACE: whoami
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
1. Get the application URL by running these commands:
  export POD_NAME=$(kubectl get pods --namespace whoami -l "app=whoami,release=whoami" -o jsonpath="{.items[0].metadata.name}")
  echo "Visit http://127.0.0.1:8080 to use your application"
  kubectl port-forward $POD_NAME 8080:80

Prove the results

For well-maintained repos as the stable or bitnami we installed earlier the usage instructions are usually properly maintained and accurate but in this case we need a few modifications to make it work. Execute:

export POD_NAME=$(kubectl get pods -l "app.kubernetes.io/name=whoami" -n whoami -o jsonpath="{.items[0].metadata.name}")
kubectl port-forward $POD_NAME 8080:80 -n whoami --address=0.0.0.0

Opening http://192.168.1.100:8080 in a browser
(or execute curl http://192.168.1.100:8080 in a terminal) results in:

Hostname: whoami-7b6ff5b56d-675pv
IP: 127.0.0.1
IP: ::1
IP: 10.1.43.16
IP: fe80::3c45:2eff:fe04:aef3
RemoteAddr: 127.0.0.1:38018
GET / HTTP/1.1
Host: 192.168.1.100:8080
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/81.0.4044.138 Chrome/81.0.4044.138 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cache-Control: max-age=0
Connection: keep-alive
Upgrade-Insecure-Requests: 1

Checking charts installed

Get a list of installed charts

helm list --all-namespaces

NAME      	NAMESPACE     	REVISION	UPDATED                                 	STATUS  	CHART              	APP VERSION
metallb   	metallb-system	1       	2020-07-03 17:49:28.611030201 +0200 CEST	deployed	metallb-0.12.0     	0.8.1      
nginx-helm	ingress-nginx 	1       	2020-07-03 17:58:48.486130759 +0200 CEST	deployed	ingress-nginx-2.9.1	0.33.0     
whoami    	whoami       	1       	2020-07-07 13:30:21.940717018 +0200 CEST	deployed	whoami-0.3.2       	v1.4.0     

Uninstall a chart

helm uninstall whoami --namespace=whoami

Checking repos installed

Get a list of installed repos

helm repo list

NAME         	URL                                             
stable       	https://kubernetes-charts.storage.googleapis.com
bitnami      	https://charts.bitnami.com/bitnami              
ingress-nginx	https://kubernetes.github.io/ingress-nginx      
halkeye      	https://halkeye.github.io/helm-charts/          

Uninstall a repository

helm repo remove halkeye