RKE2 OS Upgrade Process

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Environment

RKE2 cluster, either standalone or Rancher provisioned.

Situation

You need to upgrade or patch your RKE2 cluster nodes operating system.

Resolution

Below are listed the steps required to upgrade or patch the underlying operating system of the RKE2 cluster nodes.

After upgrading each nodes, worker or controlplane/etcd, you should check that the node and cluster are healthy before upgrading the next node.

The steps to upgrade or patch the operating system are:

During the OS upgrade, don't stop the RKE2-Server or RKE2-agent services.
Drain worker nodes before upgrading them.
Wait for the pods to be drained and scheduled to other nodes before upgrading the drained worker.
Perform the upgrade in a rolling fashion:
1. Start upgrading a single controlplane/etcd node at a time
2. Upgrade one or more workers at a time (depending on the capacity within the cluster to reschedule workloads to other nodes)
Reboot the node after the upgrade is completed.
Uncordon the node

Draining nodes during the operating system upgrade:
Your controlplane/etcd nodes are not running with the worker role, so do not run any user workloads.
Whilst the cluster-agent scheduled on these nodes runs as Deployment of two replicas on separate nodes. As a result, you do not need to drain controlplane/etcd nodes.

Special care if Longhorn is installed:
If Longhorn is installed on the cluster, please take a look at any requirement on the longhorn documentation related to the version you are using.
Especially the part concerning the drain.
https://longhorn.io/docs/1.4.4/volumes-and-nodes/maintenance/#upgrading-kubernetes

Disclaimer

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