update the kep to move to remove cgroup v1 support as our end goal

Author: kannon92

keps/sig-node/5573-cgroup-v1-unsupported/README.md

@@ -1,4 +1,4 @@
-# KEP-5573: Move cgroup v1 to unsupported
+# KEP-5573: Remove cgroup v1
 
 <!-- toc -->
 - [Release Signoff Checklist](#release-signoff-checklist)
@@ -9,18 +9,18 @@
 - [Proposal](#proposal)
   - [Risks and Mitigations](#risks-and-mitigations)
 - [Design Details](#design-details)
-  - [Enable fail-cgroup-v1 by default](#enable-fail-cgroup-v1-by-default)
+  - [Enable FailCgroupV1 by default](#enable-failcgroupv1-by-default)
   - [Update warning messages and events](#update-warning-messages-and-events)
   - [Documentation updates](#documentation-updates)
+  - [Removal of cgroup v1](#removal-of-cgroup-v1)
   - [Test Plan](#test-plan)
       - [Prerequisite testing updates](#prerequisite-testing-updates)
       - [Unit tests](#unit-tests)
       - [Integration tests](#integration-tests)
       - [e2e tests](#e2e-tests)
   - [Graduation Criteria](#graduation-criteria)
-    - [Alpha](#alpha)
     - [Beta](#beta)
-    - [GA](#ga)
+    - [Stable](#stable)
   - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
   - [Version Skew Strategy](#version-skew-strategy)
 - [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire)
@@ -75,7 +75,11 @@ Items marked with (R) are required *prior to targeting to a milestone / release*
 
 ## Summary
 
-Formally move cgroup v1 into an unsupported state in Kubernetes, building upon the maintenance mode introduced in KEP-4569. This enhancement will disable cgroup v1 support by default and provide clear messaging that cgroup v1 is no longer supported.
+Remove cgroup v1 support from Kubernetes codebase, building upon the maintenance mode introduced in KEP-4569. This enhancement will remove cgroup v1 support.
+
+This KEP will have a phased approach where beta will prevent kubelet from starting on a cgroup v1 node.
+
+In n+3 releases, we will remove the cgroup v1 code.
 
 ## Motivation
 
@@ -84,10 +88,10 @@ Following the transition of cgroup v1 support to maintenance mode in KEP-4569, t
 The motivation builds on the rationale established in KEP-4569:
 - The Linux kernel community has made cgroup v2 the focus for new features
 - Major Linux distributions are phasing out cgroup v1 support
-- systemd and other critical components are moving beyond cgroup v1
+- [systemd](https://github.com/systemd/systemd/releases/tag/v258) and other critical components are moving beyond cgroup v1
 - cgroup v2 offers better functionality, more consistent interfaces, and improved scalability
 
-By formally moving cgroup v1 to unsupported status, Kubernetes provides a clear signal to the community about the deprecation path and encourages migration to the more secure and efficient cgroup v2 technology.
+By removing cgroup v1, Kubernetes provides a clear signal to the community about the removal path and encourages migration to the more secure and efficient cgroup v2 technology.
 
 ### Goals
 
@@ -103,15 +107,16 @@ By formally moving cgroup v1 to unsupported status, Kubernetes provides a clear
 
 6. **Remove testing cgroup v1**: Moving to unsupported means that Kubernetes will no longer run tests on cgroup v1 nodes.
 
+7. **Remove cgroup v1 code**: Removing the code is the next logic step once we stop testing it. This will clean up
+the codebase.
+
 ### Non-Goals
 
-- Complete removal of cgroup v1 code (this will be addressed in a future KEP)
-- Breaking existing clusters that explicitly enable cgroup v1 support
-- Removing the ability to override the default behavior
+NA.
 
 ## Proposal
 
-This proposal builds upon the foundation laid by KEP-4569 (Moving cgroup v1 support into maintenance mode) and formally transitions cgroup v1 from maintenance mode to unsupported status.
+This proposal builds upon the foundation laid by KEP-4569 (Moving cgroup v1 support into maintenance mode) and formally removes cgroup v1 code from kubelet.
 
 ### Risks and Mitigations
 
@@ -180,6 +185,14 @@ Update all relevant documentation across the Kubernetes ecosystem:
 - Release notes
 - Blog posts about the transition
 
+### Removal of cgroup v1
+
+<UNRESOLVED @haircommander>
+Once all supported releases of Kubernetes have `FailCGroupV1` set to true, we can begin the removal of the cgroup v1 support.
+
+In this section, we should call the places where we are going to remove cgroup v1.
+</UNRESOLVED>
+
 ### Test Plan
 
 <!--
@@ -249,13 +262,17 @@ We expect no non-infra related flakes in the last month as a GA graduation crite
 
 ### Graduation Criteria
 
-#### GA
+#### Beta
 
 - Default value for `FailCgroupV1` changed to `true`
 - Updated warning messages and events for unsupported status
 - Documentation updates in kubernetes/enhancements repository
 - All e2e testing removed for cgroup v1.
 
+#### Stable
+
+- Remove all cgroup v1 related code.
+
 ### Upgrade / Downgrade Strategy
 
 <!--
@@ -460,7 +477,7 @@ This feature operates at the kubelet level and does not depend on API server or
 
 ## Implementation History
 
-- **2025-09-26**: KEP for moving cgroup v1 to unsupported status created
+- **2025-09-26**: KEP for removing cgroup v1 created
 
 ## Drawbacks
 

keps/sig-node/5573-cgroup-v1-unsupported/kep.yaml

@@ -16,7 +16,7 @@ approvers:
   - "@dchen1107"
 
 # The target maturity stage in the current dev cycle for this KEP.
-stage: stable
+stage: beta
 
 see-also: [
   "keps/sig-node/4569-cgroup-v1-maintenance-mode/README.md",
@@ -29,7 +29,7 @@ latest-milestone: "v1.35"
 
 # The milestone at which this feature was, or is targeted to be, at each stage.
 milestone:
-  stable: "v1.35"
+  beta: "v1.35"
 
 # The following PRR answers are required at alpha release
 # List the feature gate name and the components for which it must be enabled