Three Big Concepts
A Chart is a helm package.
A Repo is a place where these charts get collected and shared.
A Release is an instance of a chart running in a Kubernetes cluster.
Directory Structure
wordpress/
Chart.yaml
LICENSE
README.md
values.yaml
values.schema.json
charts/
crds/
templates/
templates/NOTES.txt
Manage Repo
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo list
helm repo remove <repo-name>
helm repo update
helm repo remove
helm repo index
Manage Chart
helm create <chart-name>
helm search repo <chart-name>
helm search repo <repo-name>
helm search hub <chart-name>
helm show/inspect all/chart/crds/readme/values <chart-name>
helm show all bitnami/wordpress
helm show values bitnami/wordpress
helm show chart bitnami/wordpress
helm show readme bitnami/wordpress
helm template <chart-name>
Managing Releases
helm install <release-name> <chart-name>/<local-chart-path>
helm list
helm uinstall <release-name>
helm history <release-name>
helm rollback <release-name> <revision>
helm get all/hooks/manifest/notes/values <release-name>
helm get manifest happy-panda
helm install --dry-run --disable-openapi-validation <release-name> <chart-name>
Helm Built-in Objects
Objects are passed into a template from the template engine. The built-in values always begin with a capital letter. This is in keeping with Go's naming convention.
Release: This object describes the release itself. It has several objects inside of it:
Release.Name
Release.Namespace
Release.IsUpgrade
Release.IsInstall
Release.Revision
Release.Service
Values: Values passed into the template from the values.yaml file and from user-supplied files. By default, Values is empty.
Chart: The contents of the Chart.yaml file. Any data in Chart.yaml will be accessible here.
Files:
Files.Get is a function for getting a file by name (.Files.Get config.ini)
Files.GetBytes is a function for getting the contents of a file as an array of bytes instead of as a string. This is useful for things like images.
Files.Glob is a function that returns a list of files whose names match the given shell glob pattern.
Files.Lines is a function that reads a file line-by-line. This is useful for iterating over each line in a file.
Files.AsSecrets is a function that returns the file bodies as Base 64 encoded strings.
Files.AsConfig is a function that returns file bodies as a YAML map.
Capabilities: This provides information about what capabilities the Kubernetes cluster supports.
Capabilities.APIVersions is a set of versions.
Capabilities.APIVersions.Has $version indicates whether a version (e.g., batch/v1) or resource (e.g., apps/v1/Deployment) is available on the cluster.
Capabilities.KubeVersion and Capabilities.KubeVersion.Version is the Kubernetes version.
Capabilities.KubeVersion.Major is the Kubernetes major version.
Capabilities.KubeVersion.Minor is the Kubernetes minor version.
Capabilities.HelmVersion is the object containing the Helm Version details, it is the same output of helm version
Capabilities.HelmVersion.Version is the current Helm version in semver format.
Capabilities.HelmVersion.GitCommit is the Helm git sha1.
Capabilities.HelmVersion.GitTreeState is the state of the Helm git tree.
Capabilities.HelmVersion.GoVersion is the version of the Go compiler used.
Template: Contains information about the current template that is being executed
Template.Name: A namespaced file path to the current template (e.g. mychart/templates/mytemplate.yaml)
Template.BasePath: The namespaced path to the templates directory of the current chart (e.g. mychart/templates).
Helm Lookup functions
template functions list: https://helm.sh/docs/chart_template_guide/function_list/
<function-name> arg1 arg2...
default "default value" .Values.<value>
lookup "apiVersion", "kind", "namespace", "name" -> resource or resource list
eg: lookup "v1" "Pod" "mynamespace" "mypod" => equivalent to: kubectl get pod mypod -n mynamespace
Operators Functions
eq, ne, lt, gt, and, or
Named Templates
{{- define "MY.NAME" }}
{{- end }}
{{- template "MY.NAME" }}
{{- template "MY.NAME" . }}
{{ include "MY.NAME" . | indent 4 }}
Helm Passing the values
There are two ways to pass values one is using values.yml file and the other is –set flag. If both are used, --set values are merged into --values with higher precedence. Overrides specified with --set are persisted in a ConfigMap. Values that have been --set can be viewed for a given release with helm get values <release-name>. Values that have been --set can be cleared by running helm upgrade with --reset-values specified.
helm install -f values.yaml local-mysql bitnami/mysql -set db.auth.username="sth", db.auth.password="supersecret"
