machineset

A machineset is a resource used in the Kubernetes Cluster API to define and manage a scalable group of machines (nodes) that share the same configuration. It provides a way to provision and maintain a set of machines across different infrastructure providers, such as cloud or on‑premises, in a consistent manner.

A machineset specifies a desired number of replicas, a label selector, and a template that describes the machine to be created. The template contains provider-specific configuration, including the machine’s operating system, size or instance type, image, and bootstrap or initialization details. The template is used to create new machines that join the target cluster. The machineset operates similarly to a Kubernetes ReplicaSet, but for entire machines rather than pods.

Operation and lifecycle are driven by a machine controller. When the replicas count increases, the controller provisions new machines according to the template. When the count decreases, it deprovisions excess machines. Machine updates and upgrades may involve replacing machines if the underlying configuration changes; in many workflows this behavior is coordinated by a higher-level object such as a MachineDeployment.

In practice, a machineset is a building block within the Cluster API. A MachineDeployment may manage one or more machinesets to implement rolling updates and versioned upgrades of the node pool. The machineset itself focuses on the consistent provisioning and lifecycle management of a cohort of machines, abstracting provider details behind the template.

Status fields typically include replicas, readyReplicas, updatedReplicas, unavailableReplicas, and conditions that reflect the observed state and health of the managed machines. See also MachineDeployment, Cluster API, and provider-specific infrastructure APIs.