errno 15 (ENOTBLK): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: mount was given a source that is not a block device where one is required.

Could be also:
Constant	Type	OS
ERROR_INVALID_DRIVE	Win32 error	Windows
KERN_INVALID_NAME	Kern return	Mac
ippStsLSFLowAndHigh	Intel Ipp Status	Any
ENOTBLK	errno	Mac
ENOTBLK	errno	Solaris
SPIN_LOCK_ALREADY_OWNED	BugCheck Code	Windows

Previous	Next
EAGAIN	ETXTBSY

ENOTBLK

ENOTBLK is most useful when diagnosing mount and storage setup failures. Linux mount(2) documents it for the case where the source is not a block device although the operation requires one. That points at the object named by the mount source, not at the target directory.

Do not treat this as a generic permission or filesystem-type problem. A path can exist and still be the wrong kind of special file. Check whether the source is a block device, whether a loop device or device-mapper node was expected, and whether the command accidentally passed a regular file, character device, stale symlink, or user-space mount helper argument.

Useful checks

Record the exact source and target arguments passed to mount() or the mount helper.
Check stat output for the source path and confirm block-device type.
For image files, confirm that a loop device was created and that the loop node, not the image path, was passed when a block device is required.
Compare with ENODEV, which more often points at an unsupported filesystem type or missing kernel support.

Linux mount(2) · Linux errno(3) · Linux UAPI errno definitions

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