Built-in Objects

Helm exposes objects like .Values, .Release, .Chart, and .Capabilities that templates can read.

Syntax{{ .Release.Name }} {{ .Chart.Version }}

Beyond your own values, Helm injects several built-in objects into every template. They all hang off the root context (the dot).

The main objects

  • .Values — the merged values (from values.yaml, -f files, and --set).
  • .Release — data about this release: .Release.Name, .Release.Namespace, .Release.Revision, .Release.IsUpgrade, .Release.IsInstall.
  • .Chart — fields from Chart.yaml: .Chart.Name, .Chart.Version, .Chart.AppVersion.
  • .Capabilities — what the target cluster supports, e.g. .Capabilities.KubeVersion.
  • .Files — access to non-template files in the chart.
  • .Template — info about the current template being rendered.

Example

Example · yaml
metadata:
  name: {{ .Release.Name }}-{{ .Chart.Name }}
  namespace: {{ .Release.Namespace }}
  labels:
    chart-version: {{ .Chart.Version }}
    app-version: {{ .Chart.AppVersion }}
    revision: "{{ .Release.Revision }}"

When to use it

  • A chart author uses {{ .Release.Name }} to prefix every resource name so multiple releases of the same chart can coexist in the same namespace without name collisions.
  • A template uses {{ .Chart.AppVersion }} to embed the application version in a Pod label, making it easy to filter Pods by version in kubectl or Datadog.
  • A developer checks {{ .Capabilities.KubeVersion.Minor }} to render different apiVersion fields for PodDisruptionBudget depending on whether the cluster supports the newer policy/v1 API.

More examples

Use Release and Chart objects

Uses built-in .Release and .Chart objects to generate unique names and standard labels without hardcoding values.

Example · yaml
# templates/deployment.yaml
metadata:
  name: {{ .Release.Name }}-app
  namespace: {{ .Release.Namespace }}
  labels:
    helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
    app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}

Capabilities version check

Selects the correct PodDisruptionBudget apiVersion based on the cluster's Kubernetes version using .Capabilities.

Example · yaml
{{- if semverCompare ">=1.21-0" .Capabilities.KubeVersion.GitVersion }}
apiVersion: policy/v1
{{- else }}
apiVersion: policy/v1beta1
{{- end }}
kind: PodDisruptionBudget

Files object for config data

Reads a static file from the chart directory using the .Files built-in object and embeds its content in a ConfigMap.

Example · yaml
# templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Release.Name }}-config
data:
  app.conf: |
    {{- .Files.Get "files/app.conf" | nindent 4 }}

Related

helm go templateshelm values file

Discussion

  • Be the first to comment on this lesson.