Helm Chart Reference

The values passed into the chart via values.yaml, --set flags, or -f overrides. This is the primary source of chart configuration.

image: {{ .Values.image.repository }}:{{ .Values.image.tag }}

Metadata about the release. Key fields: .Release.Name, .Release.Namespace, .Release.IsInstall, .Release.IsUpgrade, .Release.Revision.

app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/version: {{ .Chart.AppVersion }}

Contents of Chart.yaml. Key fields: .Chart.Name, .Chart.Version, .Chart.AppVersion, .Chart.Description.

helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}

Information about the Kubernetes cluster capabilities. Key: .Capabilities.KubeVersion.Major, .Minor, and .Capabilities.APIVersions.Has.

{{- if .Capabilities.APIVersions.Has "batch/v1/CronJob" }}
apiVersion: batch/v1
{{- end }}

Information about the current template. Key fields: .Template.Name (path), .Template.BasePath.

# Template: {{ .Template.Name }}

Renders a named template and returns the result as a string. Use over template when you need to pipe the result through further functions.

labels:
  {{- include "mychart.labels" . | nindent 4 }}

Encodes a value as a YAML string. Commonly used with nindent or indent to render nested structures from Values.

resources:
  {{- toYaml .Values.resources | nindent 2 }}

Returns the value if set and non-empty; otherwise returns the specified default. Essential for making templates resilient to missing values.

replicas: {{ .Values.replicas | default 1 }}
image: {{ .Values.image.tag | default "latest" }}

Fails template rendering with a message if a value is empty. Forces callers to provide mandatory values.

host: {{ required "A hostname is required" .Values.ingress.host }}

Wraps a string value in double quotes. Ensures YAML strings containing special characters are properly quoted.

env:
  - name: LOG_LEVEL
    value: {{ .Values.logLevel | quote }}

Like indent but prepends a newline. Pair with toYaml for clean multi-line block rendering.

spec:
  template:
    spec:
      containers:
        {{- toYaml .Values.extraContainers | nindent 8 }}

Renders a string as a Helm template. Allows values.yaml entries to contain template expressions.

{{- tpl .Values.configTemplate . }}

Queries the Kubernetes API during rendering. Returns a resource object or empty dict if not found.

{{- $secret := lookup "v1" "Secret" .Release.Namespace "my-secret" }}
{{- if $secret }}existing{{ end }}

Iterates over a list or map. Sets . to the current item (list) or provides key/value variables (map).

{{- range .Values.ports }}
- containerPort: {{ . }}
{{- end }}

Changes the scope of . to the given value. Skips the block if the value is empty — useful for optional config sections.

{{- with .Values.nodeSelector }}
nodeSelector:
  {{- toYaml . | nindent 2 }}
{{- end }}

define creates a named template block (usually in _helpers.tpl). include renders it; template renders without returning a value.

{{- define "mychart.labels" -}}
app: {{ .Chart.Name }}
release: {{ .Release.Name }}
{{- end }}

Runs before any resources are installed. Useful for schema migrations, secret seeding, or prerequisites.

annotations:
  "helm.sh/hook": pre-install
  "helm.sh/hook-weight": "-5"
  "helm.sh/hook-delete-policy": hook-succeeded

Runs after all installation resources are created. Commonly used for smoke tests or post-setup config.

annotations:
  "helm.sh/hook": post-install
  "helm.sh/hook-delete-policy": before-hook-creation

Runs before an upgrade is applied. Suitable for draining jobs, backup tasks, or locking checks.

annotations:
  "helm.sh/hook": pre-upgrade

Runs after a successful upgrade. Use for cache warming, notification sending, or validation.

annotations:
  "helm.sh/hook": post-upgrade
  "helm.sh/hook-delete-policy": hook-succeeded

Marks a Pod manifest as a Helm test. Run with helm test <RELEASE>. Pod must exit 0 for the test to pass.

annotations:
  "helm.sh/hook": test
spec:
  containers:
    - name: test-conn
      image: busybox
      command: ['wget', 'http://{{ .Release.Name }}-svc']