RKE2 OS Upgrade Process

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Environment

A Rancher-provisioned or standalone RKE2 cluster

Situation

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

Resolution

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

After upgrading each node, whether a worker or controlplane/etcd node, 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 as follows:

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 by upgrading a single controlplane/etcd node at a time
2. Upgrade one or more workers at a time (depending upon the capacity within the cluster to reschedule workloads to other nodes)
Reboot the node after the upgrade is completed
Un-cordon the node

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

Special care if Longhorn is installed:
If Longhorn is installed on the cluster, please take a look at the upgrade requirements in the Longhorn documentation related to the version you are using, in particular the section concerning draining nodes: https://longhorn.io/docs/1.6.2/maintenance/maintenance/#updating-the-node-os-or-container-runtime

Disclaimer

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