Helm

The package manager for Kubernetes, e.g.

helm install wpdemo stable/wordpress

helm status wpdemo

NAME: wpdemo
LAST DEPLOYED: May 25 15:06:44 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
NOTES:
This Helm chart is deprecated

Charts

A scaffold of K8s resources that will be installed in a specific sequence along its dependencies.

Create a Chart

A typical chart contains:

mychart/
├── Chart.yml # info about the chart: version, dependencies
├── LICENSE  
├── README.md 
├── charts # dependencies are kept here
├── crds # custom resource definitions
├── templates # manifest templates to be passed into the template engine, mixed with values.yaml
│   └── NOTES.txt # for the message shown after install
├── values.schema.json # optional 
└── values.yaml # predefined values to use with templates, override with command line flag values

or create via helm create mydemo which is an minimal chart for nginx with default values. Install via `helm install mydemo ./mydemo/

tip: Use --dry-run to generate and review the manifest

Changing values in charts

1. Inline using the flag --set: Useful for testing and development
2. Passing a file with --f: Overrides the values.yml file
3. Unpack the chart and make changes permanent, make sure to bump versions

tip: Use helm show values to check what can be changed and structure

example 1:

helm install mydemo ./mydemo/ --set image.tag=latest --dry-run

example 2:

helm install mydemo ./mydemo/ -f newvalues.yaml

cat newvalues.yaml
image:
  tag: latest

Creating charts

1. Create a regular K8s resource files: deploy, svc
2. Create a Helm chart, and substitute values with placeholders such as {{.Values.deploy.name}}
3. Verify with helm show values and helm create __ __ --dry-run
4. Compare dry-run output and initial resource file

e.g.,

helm show values

Service:
  type: LoadBalancer
  port: 80
  targetPort: 2368
  nodePort: 30080
Blog:
  name: blog
  labels: blog
  replicas: 1
  image: ghost:2.6-alpine
  imagePullPolicy: Always
  containerPort: 2368
  
helm install demo ghost --set Service.type=NodePort --dry-run

# manifest with service NodePort

helm install demo ghost --set Service.type=NodePort

NAME: demo
LAST DEPLOYED: Sat Jul 26 00:54:20 2019
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

Subcharts

Are standalone charts on their own:

• Can't access main chart or other chart values
• Parent chart can override it's values
• global values can be accessed by all charts

Chart Repositories

A collection of charts with an index, it could be any repository (e.g., a GitHub repo).  Manage chart repo via commands:

• helm repo add bitnami https://charts.bitnami.com/bitnami: add a repo to your local installations
• helm repo list: See all your local repo sources
• helm repo update: Get latest updates for local repos
• helm repo delete bitnami: Remove the repo from local sources

Install from a chart repo

helm install my-nginx bitnami/nginx: Install a specific chart from a repo

helm ls
NAME            	NAMESPACE	REVISION	UPDATED                             	STATUS  	CHART      	APP VERSION
my-nginx        	default  	1       	2020-02-25 14:53:56.584043 +0800 CST	deployed	nginx-9.4.1	1.21.1

Find a chart in a repo

helm search repo nginx: Will search across all repos in your environment

NAME                            	CHART VERSION	APP VERSION	DESCRIPTION
bitnami/nginx                   	9.4.1        	1.21.1     	Chart for the nginx server
bitnami/nginx-ingress-controller	7.6.17       	0.48.1     	Chart for the nginx Ingress controller
stable/nginx-ingress            	1.41.3       	v0.34.1    	DEPRECATED! An nginx Ingress controller that us...
stable/nginx-ldapauth-proxy     	0.1.6        	1.13.5     	DEPRECATED - nginx proxy with ldapauth
stable/nginx-lego               	0.3.1        	           	Chart for nginx-ingress-controller and kube-lego
bitnami/kong                    	3.7.9        	2.5.0      	Kong is a scalable, open source API layer (aka ...
stable/gcloud-endpoints         	0.1.2        	1          	DEPRECATED Develop, deploy, protect and monitor...

Create your own repo

1. Make a public GitHub repository
2. In your local repo, place some charts as tar.gz files and generate an index:

cd my-repo
helm fetch stable/jenkins
helm fetch binami/nginx
cd ..
helm repo index ./my-repo/

3. Publish your repo as a a GitHub page and add it to your local repos

helm repo add my-repo https://myusername.github.io/my-repo

Updating a chart

Update running release (to test a change in your chart):

1. helm upgrade my-demo custom/nginx  --set image.tag='latest'
2. check new revision via helm status nginx-1625655615

to make this change permanent, update the chart, push to repo and helm update