Helm Website Documentation

Helm is a package manager for Kubernetes that allows teams to collaborate on creating, installing, and managing applications.

Core capabilities include:

• Finding prepackaged software (charts).
• Creating and hosting custom packages.
• Installing packages into any Kubernetes cluster.
• Querying clusters to view installed and running packages.
• Managing the lifecycle of packages (update, delete, rollback, or view history).

Helm is the package manager for Kubernetes. It allows you to define, install, and upgrade applications on a Kubernetes cluster, ranging from single containers to complex applications with many interdependent parts.

Key Capabilities:

• Install and manage applications: Deploy pre-packaged applications (like databases or monitoring stacks) using charts instead of manual manifests.
• Package and share applications: Bundle Kubernetes resources into versioned charts for distribution.
• Environment-specific configuration: Use the same chart across different environments (dev, staging, prod) by supplying different configuration values.
• Safe upgrades and rollbacks: Move releases to new versions and return to previous revisions if an upgrade fails.
• Dependency management: Declare and automatically install other charts that your application requires.

The Helm Go SDK allows custom software to programmatically manage Kubernetes deployments using Helm charts. The SDK is functionally separated from the Helm CLI and is designed for use in standalone tooling.

Key packages include:

• pkg/action: The primary "client" package for performing Helm actions (e.g., install, list, upgrade). This is the same package used by the Helm CLI.
• pkg/chart and pkg/chartutil: Helpers for loading and manipulating Helm charts.
• pkg/cli: Handlers for standard Helm environment variables and subpackages for managing output and values files.
• pkg/release: Defines the Release object and its various statuses.

Full API documentation is available at https://pkg.go.dev/helm.sh/helm/v4.

The Chart Template Developer's Guide is designed to teach developers how to use Helm's template language to generate Kubernetes manifest files. Manifest files are YAML-formatted resource descriptions that Kubernetes consumes.

Key areas covered in this guide include:

• The Helm template language: Understanding the syntax and logic used within templates.
• Using values: How to inject configuration data into your templates.
• Template techniques: Advanced patterns and methods for working with templates.
• Debugging: How to troubleshoot and inspect the output of your templates.

Helm provides several core commands for managing Kubernetes packages (charts):

• helm search: Search for charts in repositories.
• helm pull: Download a chart to your local directory for inspection.
• helm install: Upload and deploy a chart to a Kubernetes cluster.
• helm list: List the current releases of charts in your cluster.

The helm plugin command is used to manage client-side Helm plugins. You can use it to install, list, uninstall, update, package, or verify plugins.

Note that helm plugin is a parent command; specific actions like install or list are subcommands with their own specific flags and behaviors.

The helm registry command is used to manage authentication for OCI registries. It provides subcommands to log in to or log out from a registry, allowing Helm to interact with private container registries for chart storage and retrieval.

To perform specific authentication tasks, use the following subcommands:

• helm registry login: Authenticate with a specific registry.
• helm registry logout: Remove authentication credentials for a registry.

For detailed usage of these subcommands, refer to the specific helm registry login and helm registry logout documentation.

The helm repo command is used to manage chart repositories. It provides subcommands to add, list, remove, update, and index repositories.

Available subcommands include:

• add: Add a new chart repository.
• list: List all currently configured chart repositories.
• remove: Remove one or more chart repositories.
• update: Update local information of available charts from the repositories.
• index: Generate an index file from a directory containing packaged charts.

Helm v4 introduces several architectural improvements and new capabilities compared to v3, focusing on extensibility and modern Kubernetes patterns. Key features include:

• Redesigned Plugin System: Now supports WebAssembly (Wasm) based plugins.
• Post-renderers: These are now implemented as plugins.
• Server-Side Apply: Native support for Kubernetes server-side apply.
• Improved Resource Watching: Enhanced support for waiting based on kstatus.
• Local Content-based Caching: Improved performance for items like charts.
• Modern Logging: Uses slog, allowing the SDK to integrate with modern logging frameworks.
• Reproducible Builds: Support for reproducible and idempotent builds of chart archives.
• Updated SDK API: Includes support for multiple chart API versions (with an experimental v3 chart API version planned).

A HIP (Helm Improvement Proposal) is a design document used to propose major new features, collect community input on specific issues, or document design decisions for the Helm project.

HIPs are maintained as Markdown files in a versioned repository, providing a historical record of the proposal's evolution. They are heavily influenced by Python's PEP system but adapted for the Helm community's scale.

Helm plugins extend core functionality without requiring Go code in the Helm core. There are three primary plugin types:

1. CLI plugins (cli/v1): Add new helm sub-commands. They can leverage Helm-specific configuration and context.
2. Getter plugins (getter/v1): Extend storage and download behavior, allowing Helm to fetch Charts and Plugins from locations beyond local filesystems, OCI registries, or HTTP repositories (e.g., S3 buckets).
3. Postrenderer plugins (postrenderer/v1): Allow modification of Chart-rendered manifests after rendering but before they are sent to the Kubernetes API. This is useful for modifying community charts you do not own.

Starting with Helm 4, the plugin system uses apiVersion: v1 to facilitate easier addition of new plugin types in the future.