AttachDetach

Attachdetach refers to the attach/detach controller in Kubernetes that manages the lifecycle of persistent volume attachments to nodes. It coordinates with cloud providers and CSI drivers to ensure a volume is attached to the node where a Pod using a PVC is scheduled, and detached when the volume is no longer needed.

Operation: When a Pod uses a PVC, the attach/detach controller creates a VolumeAttachment resource for the volume and the target node. It then instructs the cloud provider API or the CSI driver to attach the underlying storage to that node. After the attach is reported complete, the kubelet on the node mounts the volume for use by the Pod. When the Pod is deleted or the volume is no longer referenced, the controller initiates detachment and, upon confirmation, detaches the device. The controller also enforces that a volume is not attached to more than one node at a time.

Scope and relationship to other components: The attach/detach controller is part of the Kubernetes control plane and historically governed in-tree volume drivers. With CSI, some drivers implement their own attach/detach logic, while the controller may still coordinate for legacy drivers or provide finalization. It relies on VolumeAttachment and PV/PVC status, as well as node information, to determine when to attach or detach.

Notes: Detachment may be affected by node availability or cloud provider constraints, which can delay or prevent detachment. Proper configuration and awareness of the underlying storage provider are important to avoid stale attachments or data integrity issues in edge cases.