This page provides an storage overview specific to the Windows operating system.
Windows has a layered filesystem driver to mount container layers and create a copy filesystem based on NTFS. All file paths in the container are resolved only within the context of that container.
- With Docker, volume mounts can only target a directory in the container, and not an individual file. This limitation does not apply to containerd.
- Volume mounts cannot project files or directories back to the host filesystem.
- Read-only filesystems are not supported because write access is always required for the Windows registry and SAM database. However, read-only volumes are supported.
- Volume user-masks and permissions are not available. Because the SAM is not shared between the host & container, there's no mapping between them. All permissions are resolved within the context of the container.
As a result, the following storage functionality is not supported on Windows nodes:
- Volume subpath mounts: only the entire volume can be mounted in a Windows container
- Subpath volume mounting for Secrets
- Host mount projection
- Read-only root filesystem (mapped volumes still support
- Block device mapping
- Memory as the storage medium (for example,
- File system features like uid/gid; per-user Linux filesystem permissions
- Setting secret permissions with DefaultMode (due to UID/GID dependency)
- NFS based storage/volume support
- Expanding the mounted volume (resizefs)
Kubernetes volumes enable complex applications, with data persistence and Pod volume sharing requirements, to be deployed on Kubernetes. Management of persistent volumes associated with a specific storage back-end or protocol includes actions such as provisioning/de-provisioning/resizing of volumes, attaching/detaching a volume to/from a Kubernetes node and mounting/dismounting a volume to/from individual containers in a pod that needs to persist data.
Volume management components are shipped as Kubernetes volume plugin. The following broad classes of Kubernetes volume plugins are supported on Windows:
In-tree volume plugins
The following in-tree plugins support persistent storage on Windows nodes: