Helm Intro

Helm basics

It’s a client-side tool
Uses kubectl to connect to your cluster
Add repos with a URL helm repo add https://...
Update repos with helm repo update
It’s basically parametrized YAML
- Helm templates are not valid YAML, so you can’t use kubectl

Jeremy Lewi: Use Kustomize, not Helm, if you can.

Terminology

chart: an application packge
release: when you install a chart. Every release has a name.

Usage

A helm chart parameterizes YAML and exposes the parameters and their defaults on the command line for you to edit.

Add a repo

 helm repo add kiamol https://kiamol.net

Inspect default values in chart

See what versions are available

% helm search repo vweb --versions  
NAME        CHART VERSION   APP VERSION DESCRIPTION
kiamol/vweb 2.0.0           2.0.0       Simple versioned web app
kiamol/vweb 1.0.0           1.0.0       Simple versioned web app

See the default values:

% helm show values kiamol/vweb --version 1.0.0                                                                            
servicePort: 8090
replicaCount: 2

Install the chart

Override default values, and name the release ch10-vweb:

 helm install --set servicePort=8010 --set replicaCount=1 ch10-vweb kiamol/vweb --version 1.0.0

See the deployment (labels omitted in below output for brevity)

% kl get deploy --show-labels                                                                                                              
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
ch10-vweb   1/1     1            1           39s

Dry runs

There is also a --dry-run flag that will generate the YAML for you.

Update the release

Use helm upgrade :

In this case we are going to increase the replica count:

% helm upgrade --set servicePort=8010 --set replicaCount=3 ch10-vweb kiamol/vweb --version 1.0.0
Release "ch10-vweb" has been upgraded. Happy Helming!
NAME: ch10-vweb
LAST DEPLOYED: Tue Dec 13 11:10:04 2022
NAMESPACE: default
STATUS: deployed
REVISION: 2
TEST SUITE: None