Subcharts & Dependencies

A chart can depend on other charts (subcharts), letting you compose an app from reusable pieces.

Real applications are built from parts — a web app plus a database, a cache, a message queue. Helm lets a chart depend on other charts, called subcharts.

Two ways to get a subchart

  • Declare it in Chart.yaml under dependencies and let Helm fetch it.
  • Drop a chart directly into the charts/ folder.

When you install the parent, all subcharts install too, as part of the same release.

A parent chart depending on subcharts for database and cacheparent chartweb apppostgresqlredisrabbitmqsubcharts
The parent chart pulls in database, cache, and queue subcharts as dependencies.

Example

Example · yaml
# Chart.yaml
apiVersion: v2
name: my-app
version: 0.1.0
dependencies:
  - name: postgresql
    version: "15.5.0"
    repository: https://charts.bitnami.com/bitnami
  - name: redis
    version: "19.0.0"
    repository: https://charts.bitnami.com/bitnami

When to use it

  • A developer declares the official Bitnami PostgreSQL chart as a dependency so their application chart installs the database automatically without requiring operators to run two separate helm install commands.
  • A platform team composes a full observability stack chart that depends on Grafana, Prometheus, and Loki subcharts, allowing one helm install to set up the entire monitoring suite.
  • A chart maintainer pins dependency versions with a semver constraint in Chart.yaml so the chart is tested against a known range of subchart versions and unexpected updates cannot break production.

More examples

Declare a dependency in Chart.yaml

Lists postgresql and redis as dependencies with semver constraints; alias lets you reference the subchart as 'db' in values.

Example · yaml
# Chart.yaml
apiVersion: v2
name: myapp
version: 1.0.0
dependencies:
  - name: postgresql
    version: "13.x.x"
    repository: https://charts.bitnami.com/bitnami
    alias: db
  - name: redis
    version: ">=17.0.0"
    repository: https://charts.bitnami.com/bitnami

Fetch and install dependencies

Runs dependency update to pull the declared subcharts into charts/, then installs the parent chart which includes all dependencies.

Example · bash
helm dependency update ./myapp
# Downloads charts into myapp/charts/
helm install my-release ./myapp -n production

List resolved dependencies

Shows each declared dependency, its resolved version, repository URL, and whether the chart archive is present in charts/.

Example · bash
helm dependency list ./myapp

Related

helm dependency updatehelm conditions tags

Discussion

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