Kubeadm 1.20.5 upgrade plan fails for versions < 1.19.x

Question

Unfortunately we installed the new Kubeadm version 1.20.5. Ask me not why, it was a mistake. Anyway. At the moment we are unable to do the upgrade plan. I am trying this via console.

kubeadm upgrade plan

[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[upgrade/config] FATAL: this version of kubeadm only supports deploying clusters with the control plane version >= 1.19.0. Current version: v1.18.8

I know the reason for that is, that my kubeadm only supports clusters with version >= 1.19.0 and i am on v1.18.8. But how can I fix that ? This is my kubeadm version -o json output

{
  "clientVersion": {
    "major": "1",
    "minor": "20",
    "gitVersion": "v1.20.5",
    "gitCommit": "6b1d87acf3c8253c123756b9e61dac642678305f",
    "gitTreeState": "clean",
    "buildDate": "2021-03-18T01:08:27Z",
    "goVersion": "go1.15.8",
    "compiler": "gc",
    "platform": "linux/amd64"
  }
}

Is there a way to downgrade the kubeadm version to 1.19.x ?

why not just use kubeadm 1.19.x or 1.18.x? uninstall the kubeadm 1.20.5 and install 1.19.x or 1.18.x. or you can just download the kubeadm 1.19.x or 1.18.x binary. — wineinlib, Apr 02 '21 at 09:48
you are absolutely right. silly me. i will update my question with the solution. But thank you buddy you made my day — Mchoeti, Apr 02 '21 at 16:05

score 2 · Answer 1 · edited Nov 15 '21 at 16:24

As wineinlib told me. The solution is tooooo simple.

I removed the newer version via

yum remove -y kubeadm-1.20.5-0 --disableexcludes=kubernetes

After that i installed the old version with

yum install -y kubeadm-1.18.17-0 --disableexcludes=kubernetes

And this allows me to do the upgrade and furhtermore to upgrade the cluster to the last valid 1.20 version. But to be fair i did the upgrade path in the following way. Installed latest 1.18.x version Upgraded to the latest 1.19.x version and last but not least implemented the last 1.20.x version.

Kubeadm 1.20.5 upgrade plan fails for versions < 1.19.x

1 Answers1