How do you perform chart updates in Helm?

Updating charts in Helm is performed with the command helm upgrade.

Main flags used during the upgrade:

• --install: If a release with the specified name does not exist, Helm will install it. Convenient for idempotency.
• --version <chart_version>: Specifies a particular chart version for the upgrade. If not specified, the latest stable version is used.
• --values <values_file>: Overrides default values in values.yaml using the specified file. Can be used multiple times.
• --set <key=value>: Overrides default values directly in the command line. Useful for small changes.
• --namespace <namespace>: Specifies the namespace where the release is located.
• --atomic: Rolls back the upgrade if it fails (e.g., due to deployment issues).
• --wait: Waits until all release resources are ready before declaring success.

Example usage:

# Upgrade the release 'my-release' in the 'default' namespace
# using a new chart version './mychart'
# and overriding 'image.tag' from 'values.yaml'
helm upgrade my-release ./mychart --namespace default --values values.yaml --set image.tag=latest

The upgrade process includes:

1. Helm downloads the specified chart version.
2. Applies overridden values (from --values files and --set flags).
3. Generates Kubernetes manifests based on chart templates and final values.
4. Sends these manifests to the Kubernetes API server.
5. Kubernetes performs a rolling update for deployed resources (e.g., Deployment).
6. When using --atomic, if deployment fails, Helm automatically rolls back to the previous working release version.

Helm keeps a history of all releases, allowing rollbacks with the helm rollback command.