VolumeAttachment

VolumeAttachment is a Kubernetes API object used to coordinate the attachment of a storage volume to a specific node. It is part of the storage.k8s.io API group and is primarily utilized by container storage interface (CSI) drivers and the Attach/Detach controller to track and manage volume attachments in the cluster. The resource records which volume is being attached, to which node, and by which driver, enabling proper orchestration of mounting and releasing volumes as pods come and go.

The VolumeAttachment object has a spec that typically includes three main fields: VolumeName, which identifies the Kubernetes volume to attach; Attacher, which indicates the driver responsible for performing the attach operation; and NodeName, which names the node to which the volume should be attached. The status portion of the object conveys the outcome of the attach operation. It includes an Attached boolean to indicate whether the volume has been successfully attached to the node, and an AttachError field that can carry error details if the attach attempt fails. Some versions may provide additional status detail, but Attached and AttachError are the core elements used by controllers to determine subsequent steps.

Lifecycle and behavior: when a pod requires a volume, the Attach/Detach controller and CSI driver work together to create and update a VolumeAttachment object. A successful attach results in status.Attached being set to true, after which the CSI driver can perform the necessary steps to make the volume available on the node. If the attach fails, AttachError is populated with diagnostic information. VolumeAttachment resources are typically managed by cluster components rather than created directly by users and are tied to the lifecycle of volumes, nodes, and CSI drivers.

In practice, VolumeAttachment helps Kubernetes coordinate volume lifecycles across nodes, enabling reliable attachment, mounting, and detachment of storage for workloads.