helm

https://github.com/helm/helm

Package manager for kubernetes

• Helm packages multiple kubernetes resources in a single deployment logical object called Chart
• Helm offers a dependency management

Glossary

• a Helm Chart is a package that contains multiple k8s resources (Deployments, Configmaps, Services, Ingress, …)
• a Release is an instance of a Chart
• a Registry is a collection of Chart
• a Template is a k8s resource model using the Golang templating engine and the library Sprig

Chart

https://helm.sh/docs/topics/charts/

Chart project structure

$ helm create hello-world
$ tree
.
|-- Chart.yaml
|-- values.yaml
|-- charts/
|   `-- redis-10.2.1.tgz
`-- templates/
    |-- NOTES.txt
    |-- _helpers.tpl
    |-- hasher.yaml
    |-- rng.yaml
    |-- serviceaccount.yaml
    |-- webui.yaml
    `-- worker.yaml

• Chart.yaml: This is the main file that contains the description of our chart
• values.yaml: this is the file that contains the default values for our chart
• templates: This is the directory where Kubernetes resources are defined as templates
• charts: This is an optional directory that may contain sub-charts
• .helmignore: This is where we can define patterns to ignore when packaging (similar in concept to .gitignore)

chart.yaml

apiVersion: The chart API version (required)
name: The name of the chart (required)
version: A SemVer 2 version (required)
kubeVersion: A SemVer range of compatible Kubernetes versions (optional)
description: A single-sentence description of this project (optional)
type: The type of the chart (optional)
keywords:
  - A list of keywords about this project (optional)
home: The URL of this projects home page (optional)
sources:
  - A list of URLs to source code for this project (optional)
dependencies: # A list of the chart requirements (optional)
  - name: The name of the chart (nginx)
    version: The version of the chart ("1.2.3")
    repository: (optional) The repository URL ("https://example.com/charts") or alias ("@repo-name")
    condition: (optional) A yaml path that resolves to a boolean, used for enabling/disabling charts (e.g. subchart1.enabled )
    tags: # (optional)
      - Tags can be used to group charts for enabling/disabling together
    import-values: # (optional)
      - ImportValues holds the mapping of source values to parent key to be imported. Each item can be a string or pair of child/parent sublist items.
    alias: (optional) Alias to be used for the chart. Useful when you have to add the same chart multiple times
maintainers: # (optional)
  - name: The maintainers name (required for each maintainer)
    email: The maintainers email (optional for each maintainer)
    url: A URL for the maintainer (optional for each maintainer)
icon: A URL to an SVG or PNG image to be used as an icon (optional).
appVersion: The version of the app that this contains (optional). Needn't be SemVer. Quotes recommended.
deprecated: Whether this chart is deprecated (optional, boolean)
annotations:
  example: A list of annotations keyed by name (optional).

Public Kubernetes package registry

https://artifacthub.io/

Useful commands

# update to latest charts
helm repo update
 
# add repo
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
 
# list charts from a repo
helm search repo prometheus-community
 
# install a chart
helm install prometheus-community/prometheus --generate-name
 
# list helm releases
helm list
helm ls
 
# show configurable options with detailed comments
helm show values prometheus-community/prometheus
 
# check helm release status
helm status prometheus
 
# uninstall a releases
helm uninstall grafana
 
# upgrading a release
helm upgrade grafana grafana/grafana --set ingress.enabled=true

The format and limitation of —set.