What happened?

First, I ensured (and reconfigured grub) to use cgroups V2:
in /etc/default/grub,
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=vg0/lv_root rhgb quiet systemd.unified_cgroup_hierarchy=1"

I then verified it is running cgroups V2:
[root@docktest01 ~]# cd /sys/fs/cgroup/
[root@docktest01 cgroup]# ll
total 0
-r--r--r-- 1 root root 0 Dec 19 17:17 cgroup.controllers
-rw-r--r-- 1 root root 0 Dec 19 17:18 cgroup.max.depth
-rw-r--r-- 1 root root 0 Dec 19 17:18 cgroup.max.descendants
-rw-r--r-- 1 root root 0 Dec 19 17:17 cgroup.procs
-r--r--r-- 1 root root 0 Dec 19 17:18 cgroup.stat
-rw-r--r-- 1 root root 0 Dec 19 17:18 cgroup.subtree_control
-rw-r--r-- 1 root root 0 Dec 19 17:18 cgroup.threads
-rw-r--r-- 1 root root 0 Dec 19 17:18 cpu.pressure
-r--r--r-- 1 root root 0 Dec 19 17:18 cpuset.cpus.effective
-r--r--r-- 1 root root 0 Dec 19 17:18 cpuset.mems.effective
-r--r--r-- 1 root root 0 Dec 19 17:18 cpu.stat
drwxr-xr-x 2 root root 0 Dec 19 17:17 init.scope
-rw-r--r-- 1 root root 0 Dec 19 17:18 io.pressure
-r--r--r-- 1 root root 0 Dec 19 17:18 io.stat
-r--r--r-- 1 root root 0 Dec 19 17:18 memory.numa_stat
-rw-r--r-- 1 root root 0 Dec 19 17:18 memory.pressure
--w------- 1 root root 0 Dec 19 17:18 memory.reclaim
-r--r--r-- 1 root root 0 Dec 19 17:18 memory.stat
drwxr-xr-x 120 root root 0 Dec 19 17:17 system.slice
drwxr-xr-x 4 root root 0 Dec 31 15:05 user.slice

And the kernel version is:
[root@docktest01 cgroup]# uname -r
4.18.0-477.58.1.el8_8.x86_64

However, when I run kubadm init it tells me that this kernel version is not supported, but then claims that the version it is running meets the requirments:
[root@docktest01 ~]# kubeadm init --pod-network-cidr 10.62.76.0/24 .
.
error execution phase preflight: [preflight] Some fatal errors occurred:
[ERROR SystemVerification]: kernel release 4.18.0-477.58.1.el8_8.x86_64 is unsupported. Recommended LTS version from the 4.x series is 4.19. Any 5.x or 6.x versions are also supported. For cgroups v2 support, the minimal version is 4.15 and the recommended version is 5.8+

So, while on one hand it states the minimum kernel version for cgroups V2 support is 4.15+, it is failing with a kernel version of 4.18, and via verification, the system is indeed using cgroups V2.

So, where is the problem? When I first had this error, I found that the system was indeed using cgroups V1, that's why I reconfigured grub, rebuilt the config and rebooted the system, only to show that it was then using V2. But am getting this incompatibility error.

Is it finding that the system is still running cgroups V1, not V2, and therefore thinking it needs to be on a 4.19 kernel? Also, since RH has not released a 4.19 kernel, is my only option an upgrade to RHEL 9?

Please assist.

What did you expect to happen?

I expected kubeadm to initialize the master node.

How can we reproduce it (as minimally and precisely as possible)?

Repeat steps taken on RHEL 8.8, with kernel 4.18 as described above.

Anything else we need to know?

No response

Kubernetes version

$ kubectl version
Client Version: v1.32.0
Kustomize Version: v5.5.0
The connection to the server localhost:8080 was refused - did you specify the right host or port?

Cloud provider

OS version

# On Linux:
$ cat /etc/os-release
# NAME="Red Hat Enterprise Linux"
VERSION="8.8 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.8"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.8 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8::baseos"
HOME_URL="https://www.redhat.com/"
DOCUMENTATION_URL="https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 8"
REDHAT_BUGZILLA_PRODUCT_VERSION=8.8
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="8.8"
$ uname -a
# Linux docktest01 4.18.0-477.58.1.el8_8.x86_64 #1 SMP Wed May 22 13:46:53 EDT 2024 x86_64 x86_64 x86_64 GNU/Linux

# On Windows:
C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture
# paste output here

Install tools

Container runtime (CRI) and version (if applicable)

Related plugins (CNI, CSI, ...) and versions (if applicable)