Running a dual boot system with OS X and Windows 10 an ExFAT data exchange partition is useful.

But from time to time (after some months in my case) theExFAT partition is gone:

  • OS X and Windows 10 list a raw partition instead of an ExFAT partition

Repair in OS X using the terminal:

  • sudo su
  • diskutil list
    (this should display a “Microsoft Basic Data” partition with the size of the disappeared ExFAT partition;
    the name column is empty; the identifier like disk0s3 has to be used in the next step)
  • fsck_exfat disk0s3
    (replace disk0s3 by your ExFAT partition)
  • when asked by fsck_exfat to repair your “Main boot region” answer “y”
  • diskutil mount disk0s3
    (replace disk0s3 by your ExFAT partition)
  • now yourExFAT partition should be back in Finder
    (which can be verified on the console with: ls /Volumes)

Details taken from this discussion.

Repair attemps on Windows could use chkdsk d: /f
(replace d: with the windows drive letter of your disappeared ExFAT partition;
use <windows key> + x to open an administrative console.)

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