The helm rollback command is the designated tool for reverting a Helm release to a previous revision. When a new version of an application deployed via Helm introduces a bug, helm rollback allows an operator to quickly and safely return the application to its last known-good state. This command increments the release revision number and updates the Kubernetes resources to match the state of the specified older revision, effectively undoing the problematic upgrade.

B. helm upgrade --force: This command is used for upgrading a release. While you could technically "upgrade" to an older chart version, rollback is the idiomatic and intended command for reverting.

C. helm template: This command renders chart templates locally for inspection and debugging. It does not interact with or modify a live Kubernetes cluster deployment.

D. helm uninstall: This command completely removes the release and all its associated resources from the cluster, which is not the goal of restoring a previous stable version.

1. Helm Documentation

"helm rollback": The official documentation explicitly states

"This command rolls a release back to a previous revision." It is the primary command for the scenario described.

Source: Helm Project Documentation

helmrollback.md. Available at: https://helm.sh/docs/helm/helmrollback/

2. Helm Documentation

"Using Helm": The official guide on managing releases describes the lifecycle

including upgrades and rollbacks. It positions helm rollback as the standard procedure for reverting a faulty helm upgrade.

Source: Helm Project Documentation

"Using Helm"

Section: "Upgrading a Release and Recovering on Failure". Available at: https://helm.sh/docs/intro/usinghelm/#upgrading-a-release-and-recovering-on-failure

3. The Linux Foundation

"Introduction to Helm (LFS171x)": This course

offered via edX

covers the fundamentals of managing applications with Helm. The module on "Managing Charts and Releases" details the use of helm rollback to revert to a previous release version as a core operational task.

Source: The Linux Foundation

edX Course LFS171x

Chapter 4: Managing Charts and Releases.