Getting Started With Helm

Helm is a tool for managing Kubernetes packages which allows to create, scale and maintain complex applications easily. To learn more about Helm and its architecture, click here.

Helm Logo — helm.sh

Installing Helm

To install helm, kubernetes must be installed and minikube should be running.
Open up the terminal type the following commands.

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3
chmod 700 get_helm.sh
./get_helm.sh

To verify the Helm installation, type helm version and press enter, you should see the helm version.

Creating PostgreSQL Chart

Type the following command.

$ mkdir helm-tutorial
$ cd helm-tutorial
$ helm create postgres
Creating postgres

You should see a directory named postgres which the following structure.

$ cd postgres
$ ls
charts  Chart.yaml  templates  values.yaml

Now lets start defining our deployment, but first delete the deployment.yml file and create and new one.

$ rm templates/deployment.yaml
$ vi templates/deployment.yaml

Paste the following code.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.postgres.name }}
  labels:
    app: {{ .Values.postgres.name }}
    group: {{ .Values.postgres.group }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Values.postgres.name }}
  template:
    metadata:
      labels:
        app: {{ .Values.postgres.name }}
        group: {{ .Values.postgres.group }}
    spec:
      volumes:
        - name: {{ .Values.postgres.volume.name }}
          persistentVolumeClaim:
            claimName: {{ .Values.postgres.volume.pvc.name }}
      containers:
        - name: {{ .Values.postgres.name }}
          image: {{ .Values.postgres.container.image }}  
          ports:
            - containerPort: {{ .Values.postgres.container.port }}
          envFrom:
            - configMapRef:
                name: {{ .Values.postgres.config.name }}
          volumeMounts:             
            - name: {{ .Values.postgres.volume.name }}
              mountPath: {{ .Values.postgres.volume.mountPath }}

To create the persistent volume claim, create a file called pvc.yml.

$ vi templates/pvc.yaml

Copy the following content.

---
apiVersion: v1
kind: {{ .Values.postgres.volume.kind }}
metadata:
  name: {{ .Values.postgres.volume.pvc.name }}
spec:
  accessModes:
    - {{ .Values.postgres.volume.pvc.accessMode }}
  resources:
    requests:
      storage: {{ .Values.postgres.volume.pvc.storage }}

To expose postgres we have to define a service, by first deleting the service.yml file and create and new one.

$ rm templates/service.yaml
$ vi templates/service.yaml

Copy the following content.

---
apiVersion: v1
kind: Service
metadata:
  name: {{ .Values.postgres.name }}
  labels: 
    group: {{ .Values.postgres.group }}
spec:
  type: {{ .Values.postgres.service.type }}
  selector:             
    app: {{ .Values.postgres.name }}
  ports:
    - port: {{ .Values.postgres.service.port }}       
      targetPort: {{ .Values.postgres.container.port }}

To provide configurations through a file, create a file called config.yml.

$ vi templates/config.yaml

Copy the following content.

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Values.postgres.config.name }}
  labels:
    group: {{ .Values.postgres.group }}
data: 
{{- range .Values.postgres.config.data }}
  {{ .key }}: {{ .value }}
{{- end}}

lets provide default values, by first deleting the values.yml file and create and new one.

$ rm values.yaml
$ vi values.yaml

Copy the following content.

---
replicaCount: 1
postgres:
  name: postgres
  group: db
  container:
    image: postgres:9.6-alpine
    port: 5432
  service:
    type: ClusterIP
    port: 5432
  volume:
    name: postgres-storage
    kind: PersistentVolumeClaim
    mountPath: /var/lib/postgresql/data
    pvc:
      name: postgres-persistent-volume-claim
      accessMode: ReadWriteOnce
      storage: 4Gi
  config:
    name: postgres-config
    data:
       - key: POSTGRES_DB
         value: RevolutionArmy
       - key: POSTGRES_USER
         value: Revolutioner
       - key: POSTGRES_PASSWORD
         value: Revolutioner

Go outside the postgres folder, i.e. helm-tutorial and create a file to override basic configurations.

$ cd ..
$ vi override-config.yaml

Copy the following content.

postgres:
    config:
        data:
            - key: POSTGRES_DB
              value: postgres
            - key: POSTGRES_USER
              value: postgres
            - key: POSTGRES_PASSWORD
              value: postgres

Now everything is ready, we can now deploy postgres but lets clean up the unused files.

$ cd postgres/templates
$ rm _helpers.tpl
$ rm hpa.yaml
$ rm ingress.yaml
$ rm NOTES.txt
$ rm serviceaccount.yaml
$ rm -rf tests

Deploying PostgreSQL Chart

When a chart is deployed to a cluster using Helm, it is called a release.

$ helm install -f override-config.yaml postgres ./postgres

You should an output something like this.

NAME: postgres
LAST DEPLOYED: Thu Jul 30 09:31:54 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

To view all the charts, type the following

$ helm list
NAME     NAMESPACE REVISION  STATUS    CHART          APP VERSION
postgres default   1         deployed  postgres-0.1.0 1.16.0

To view all the releases, type the following ( note this will also list other k8s deployments)

$ kubectl get deployments
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
postgres   1/1     1            1           2m45s