Helm: Kubernetes Package Manager

Up to now, everything in this course came from YAML we wrote ourselves. That is the right way to learn. But suppose you want to run Prometheus, Grafana or Argo CD in your cluster. Each of them needs dozens of objects: Deployments, StatefulSets, Services, ConfigMaps, Secrets, ServiceAccounts, Roles, RoleBindings, CustomResourceDefinitions, PVCs. Writing and maintaining all of that by hand, and upgrading it later, would be a full-time job.

On Linux you never install Git by downloading its files and dependencies yourself. You run apt install git on Ubuntu, or dnf install git on Amazon Linux and Red Hat. The package manager knows what to fetch and how to set it up.

Helm is the package manager for Kubernetes. It installs, upgrades, configures and uninstalls applications in your cluster with a few commands.

Three words to know

You find charts on Artifact Hub, the community catalogue. Search for "argo-cd", "prometheus" or "grafana" and you get the repository URL and the install command. Prefer charts from the project's own organisation, marked as official or verified publisher, and sorted by stars.

Inside a chart

mychart/
├── Chart.yaml          # name, version, appVersion, description
├── values.yaml         # default settings, all of them overridable
├── templates/          # Kubernetes YAML with {{ placeholders }}
│   ├── deployment.yaml
│   ├── service.yaml
│   └── _helpers.tpl
└── charts/             # other charts this one depends on

A template looks like ordinary YAML with placeholders:

spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"

helm install fills the placeholders from values.yaml and from anything you pass with --set or -f my-values.yaml, then sends the resulting YAML to the cluster. That is why one chart can serve dev, test and production: only the values change.

Install Helm on the EKS home server

Helm is a single binary on the machine where you run kubectl. It talks to the cluster using the same kubeconfig. Nothing is installed inside the cluster for Helm itself.

The lecture uses the official install script:

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

Downloading https://get.helm.sh/helm-v3.21.3-linux-amd64.tar.gz
Verifying checksum... Done.
Preparing to install helm into /usr/local/bin
helm installed into /usr/local/bin/helm
version.BuildInfo{Version:"v3.21.3", ...}

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-4
chmod 700 get_helm.sh
./get_helm.sh

The commands you will use

A quick practice run with your own chart

You do not need a repository to try Helm. helm create generates a working sample chart that deploys nginx:

helm create telusko-chart
ls telusko-chart
helm install telusko-web ./telusko-chart
helm list
kubectl get deploy,svc,pods

Change a value during an upgrade, then look at the history and roll back:

helm upgrade telusko-web ./telusko-chart --set replicaCount=3
kubectl get pods                       # 3 pods now
helm history telusko-web
helm rollback telusko-web 1
kubectl get pods                       # back to 1 pod
helm uninstall telusko-web

helm upgrade --install installs if the release does not exist yet and upgrades if it does. Pipelines use it so the same command works on the first and every later deployment.

In the next lesson we use Helm for real: installing Argo CD with two commands instead of hundreds of lines of YAML.

Try It Yourself

1. Install Helm and run helm version. Which major version did you get?
2. Add the Argo repository, run helm repo update, and helm search repo argo. How many charts does the project publish?
3. Run helm show values argo/argo-cd | less and find the setting that controls the type of the argocd-server Service.
4. Create telusko-chart, change replicaCount to 2 in its values.yaml, and use helm template to see the rendered Deployment before installing it.
5. Install it, upgrade it twice with different values, and roll back to revision 2. Check with helm history.

Official references

• Helm: Installing Helm
• Helm: Quickstart Guide
• Helm: Charts
• Helm: Helm 3 End of Life

Written By: Shramik Masti