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kIOReturnUnformattedMedia
What “unformatted” should not imply
kIOReturnUnformattedMedia means that the driver or storage layer cannot use the present medium in the format expected by that operation. It does not prove that the device is physically broken, nor does it authorize an application to overwrite the medium. A newly initialized, foreign-format, encrypted, raw, or otherwise unsupported medium can lead to this state depending on the IOKit family and API.
The safe next step is inspection, not automatic formatting. Disk Arbitration can expose disk and IOMedia information that helps determine what object appeared. Formatting is a destructive state transition and should be performed only through an explicit user or management workflow that understands the target device and its current ownership.
What to investigate
- Identify whether the target is whole media, a partition, or a logical volume before making any change.
- Read current disk properties and, where appropriate, inspect partitioning and filesystem metadata with non-destructive tools.
- Check for encryption, vendor-specific formats, and media inserted into a device that supports more than one type.
- Keep the error distinct from bad-media and no-media conditions in logs and user messages.
References
- Apple IOReturn.h reference
- Apple Disk Arbitration Programming Guide
- Apple IOKit Fundamentals: Architectural Overview
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