AKS kubernetes upgrade from v1.23.12 path

Question

We have an AKS cluster that is on kubernetes v1.23.12. I had understood that it was EoF in Sept23 but looking at https://learn.microsoft.com/en-us/azure/aks/supported-kubernetes-versions?tabs=azure-cli it would appear that v1.24.x will EoF July23 and 1.23 is already out of support.

My understanding is that when upgrading we cannot skip minor versions and must do a multi stage upgrade from 1.23 --> 1.24 --> 1.25 --> 1.26 --> 1.27 in order to get to version v1.27

My concern/question is whether with v1.24 is EOF in July23 does this block our upgrade path if we have not moved to v1.24 before it is EOF, and thus force us to upgrade at least to 1.24 before the end of July23?

So my question is two fold

1. Is my understanding that upgrades cannot skip minor versions correct meaning a v1.23 can only upgrade to v1.24 as a first step?
2. if so, then once v1.24 has gone EOF does it prevent us from upgrading the cluster from v1.23 if we have not done so prior to the v1.24 EOF date. The implication being that if so, we would have to rebuild the cluster.

Thanks in advance for your help

Daryl

Answer 1

Hello Daryl O Regan,

I will answer your questions below:

1 - Is my understanding that upgrades cannot skip minor versions correct meaning a v1.23 can only upgrade to v1.24 as a first step?

Answer: That is partially correct. You cannot skip a minor version (1.24 in this situation) as long as the version is still available. For example, I checked now in West Europe:

$az aks get-versions -l westeurope -o table

KubernetesVersion Upgrades

---

1.27.1(preview) None available

1.26.3 1.27.1(preview)

1.26.0 1.26.3, 1.27.1(preview)

1.25.6 1.26.0, 1.26.3

1.25.5 1.25.6, 1.26.0, 1.26.3

1.24.10 1.25.5, 1.25.6

1.24.9 1.24.10, 1.25.5, 1.25.6

This means that you would not be able to skip 1.24. When 1.24 will be deprecated, a cluster will be allowed to skip 1.24 and go from 1.23 to 1.25 directly.

Please read here for a better understanding: https://learn.microsoft.com/en-us/azure/aks/supported-kubernetes-versions?tabs=azure-cli#can-i-skip-multiple-aks-versions-during-cluster-upgrade
To find out when a Kubernetes version is deprecated, you can follow https://github.com/Azure/AKS/releases for announcements and https://releases.aks.azure.com/ for when a specific release propagated within a specific region.

2 - if so, then once v1.24 has gone EOF does it prevent us from upgrading the cluster from v1.23 if we have not done so prior to the v1.24 EOF date. The implication being that if so, we would have to rebuild the cluster.

Answer: As mentioned above, once 1.24 has gone EOF, you will be able to upgrade from 1.23 to 1.25 directly. However, please note as per the link sent above:
"When performing an upgrade from an unsupported version that skips two or more minor versions, the upgrade is performed without any guarantee of functionality and is excluded from the service-level agreements and limited warranty. If your version is significantly out of date, it's recommended to re-create the cluster."

Hopefully this is what you are looking for! If you have additional questions, please let us know in the comments.

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