Helm Chart
Understanding Helm charts, their role in Kubernetes package management, and how they simplify the process of deploying, managing, and scaling applications
What is a Helm Chart? Definition and explanation
Helm Chart Definition
A Helm chart is a collection of files that define, configure, and install a Kubernetes application. It consists of a set of templates, values, and other resources that are used to create the necessary Kubernetes resources for an application. Helm charts are used to package, distribute, and manage applications within Kubernetes clusters.
Helm is the de facto package manager for Kubernetes, and charts are its package format. Instead of applying dozens of raw YAML manifests by hand, you install a chart with a single helm install command and customize it through values.
What is a Helm Chart used for?
A Helm chart packages everything an application needs to run on Kubernetes: resource definitions, dependencies, and configuration defaults. Because the same chart can be installed with different values per environment, it keeps deployments consistent across development, staging, and production, and makes upgrades and rollbacks repeatable.
Example Helm Chart structure
mychart/ Chart.yaml # Required: Chart metadata (name, version, description, etc.) LICENSE # Optional: License information README.md # Optional: Documentation for the chart values.yaml # Default configuration values values.schema.json # Optional: JSON schema for validating values charts/ # Directory for chart dependencies templates/ # Kubernetes manifests and templates deployment.yaml service.yaml _helpers.tpl # Reusable template snippets NOTES.txt # Optional: Usage notes shown post-installKey Components of a Helm Chart
- Templates: Define the Kubernetes resources needed (like Deployments, Services, etc.) using Go templating. This enables customization of properties like replica count, container images, and resource limits by inserting specific values during installation.
- Values:
values.yamlholds default settings for your application. This central file allows for easy customization of templates, and you can override these defaults for different environments. - Chart.yaml: The metadata file, listing the chart’s name, version, description, and any dependencies, which supports versioning and compatibility management.
- values.schema.json: An optional schema file that validates the structure and types of the values users provide.
How are Helm Charts distributed?
Charts are published to chart repositories or, since Helm 3.8, to any OCI-compliant container registry:
helm push mychart-1.0.0.tgz oci://registry.example.com/chartshelm install myrelease oci://registry.example.com/charts/mychart --version 1.0.0Storing charts next to container images in the same registry simplifies distribution, especially for vendors shipping applications to self-hosted or air-gapped customer environments, where both the chart and its images have to be delivered together.
One thing chart authors shipping to customers learn quickly: a chart that works on your cluster may fail on a customer’s older or restricted Kubernetes version. See our guide on building a Kubernetes compatibility matrix for your Helm chart.
