[Kubernetes](Registry)Understand how to use helm chart in Kubernetes

Purpose

To understand How to use helm chart

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Helm chart directory structure

wordpress/
  Chart.yaml          # A YAML file containing information about the chart
  LICENSE             # OPTIONAL: A plain text file containing the license for the chart
  README.md           # OPTIONAL: A human-readable README file
  values.yaml         # The default configuration values for this chart
  values.schema.json  # OPTIONAL: A JSON Schema for imposing a structure on the values.yaml file
  charts/             # A directory containing any charts upon which this chart depends.
  crds/               # Custom Resource Definitions
  templates/          # A directory of templates that, when combined with values,
                      # will generate valid Kubernetes manifest files.
  templates/NOTES.txt # OPTIONAL: A plain text file containing short usage notes

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Find helm chart - helm search

helm search repo/hub [chartname]

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Download and install helm chart - helm fetch and install

Before install helm chart, you can change values.yaml file what you want

helm fetch [helmchart]
helm install [helmchart] .[chart-path] -n [namespace]
helm uninstall [helmchart] -n [namespace]

Option

• template debug
  1. lint : verify template and dependencies
  2. –dry-run : you can see template yaml files and error

1. helm lint prometheus-operator
2. helm install prometheus-operator

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Helm upgrade - After edit value.yaml

helm upgrade -n prometheus prometheus -f ./values.yaml ./ --dry-run

helm history -n prometheus prometheus
REVISION        UPDATED                         STATUS          CHART                           APP VERSION     DESCRIPTION
1               Fri Apr  2 13:17:14 2021        superseded      prometheus-operator-9.3.2       0.38.1          Install complete
2               Fri Apr  2 13:24:14 2021        deployed        prometheus-operator-9.3.2       0.38.1          Upgrade complete

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Do not remove resource such as pvc

metadata:
  annotations:
    "helm.sh/resource-policy": keep
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