Performing a Control Plane Only update

Due to fundamental Kubernetes design, all {product-title} updates between minor versions must be serialized. You must update from {product-title} <4.y> to <4.y+1>, and then to <4.y+2>. You cannot update from {product-title} <4.y> to <4.y+2> directly. However, administrators who want to update between two even-numbered minor versions can do so incurring only a single reboot of non-control plane hosts.

Important

This update was previously known as an EUS-to-EUS update and is now referred to as a Control Plane Only update. These updates are only viable between even-numbered minor versions of {product-title}.

There are several caveats to consider when attempting a Control Plane Only update.

Control Plane Only updates are only offered after updates between all versions involved have been made available in stable channels.
If you encounter issues during or after updating to the odd-numbered minor version but before updating to the next even-numbered version, then remediation of those issues may require that non-control plane hosts complete the update to the odd-numbered version before moving forward.
You can do a partial update by updating the worker or custom pool nodes to accommodate the time it takes for maintenance.
Until the machine config pools are unpaused and the update is complete, some features and bugs fixes in <4.y+1> and <4.y+2> of {product-title} are not available.
All the clusters might update using EUS channels for a conventional update without pools paused, but only clusters with non control-plane MachineConfigPools objects can do Control Plane Only updates with pools paused.