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Fix corrupted exFAT disk macOS/OSX
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fix_exfat_drive.md

exFAT support on macOS seems to have some bugs because my external drives with exFAT formatting will randomly get corrupted.

If Disk Utility is unable to repair, consider trying this:

  1. In Disk Utility, ensure that the drive is not mounted, eject it if it is mounted.
  2. Use diskutil list to find the right drive id.
  3. You want the id under the IDENTIFIER column, it should look like disk1s1
  4. Run sudo fsck_exfat -d <id from above>. eg sudo fsck_exfat -d disk1s3
  5. -d is debug so you'll see all your files output as they're processed.
  6. Answer YES if it gives you the prompt Main boot region needs to be updated. Yes/No?
  7. Open Disk Utility and you should be able to repair here successfully.

See the apple man page below for details on the fsck_exfat utility.

Sources/Extra Reading: https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man8/fsck_exfat.8.html https://craigsmith.id.au/2014/07/06/repairing-a-corrupted-mac-osx-exfat-partition/ https://discussions.apple.com/thread/4154638?tstart=0

@Harsha345155
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@edubskiy I tried your way but it's showing
zsh: unknown file attribute: b

I am lost.

@pmaingi
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pmaingi commented Feb 3, 2023

@krsnk — Did you try from the Terminal:
diskutil list
The volumes listed should show your disk ("rdisk2s1") and possibly its partitions.
Then, copy paste this (replace "disk2") in the example below with your disk's or partition's name (of course, remove "(but your disk)").

sudo ps -ax | grep disk2 (but your disk)

you should get the process number keeping your disk busy:
13699 ?? 11:52.83 /System/Library/Filesystems/hfs.fs/Contents/Resources/./fsck_hfs -y /dev/disk2s2
Then execute:
sudo kill 13699
In the example above, "13699" refers to the process currently busy, but it should be a different number on your machine.
After killing the process, the drive should mount, with a Finder's warning.

Thanks, man. You saved my day!

Thank you, i can now access my flash drive.

@edgarlim
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edgarlim commented Feb 3, 2023 via email

@alexisdray
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@gg4u just ran into the same issue, did you ever sort that out?
wondering whether to pull the plug and just reformat

@sergeydgr8
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I'm running into a similar issue as @gg4u where fsck_exfat fails:

--- [1] Evicted 1 buffers (262144 bytes; 16 pages)
Read      offset = 0x00000a036000  length = 0x001000
Assertion failed: (result != NULL), function fsck_exfat_cache_recycle, file fsck_exfat_cache.c, line 349.
[1]    24285 abort      sudo fsck_exfat -dy disk4s2

The debug logs show that it fails on the exact same file. Anyone have advice on how to combat this?

@fitnessbimbo
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Started with error
Checking volume.
** Checking main boot region.
fsck_exfat: Could not read boot region
** The volume could not be verified completely.

I've done all of the above with no luck. The latest error I get when I run diskutil verifyDisk /dev/disk2 is

Nonexistent, unknown, or damaged partition map scheme
If you are sure this disk contains a (damaged) APM, MBR, or GPT partition
scheme, you might be able to repair it with "diskutil repairDisk /dev/disk2"

I run diskutil repairDisk /dev/disk2 and get

Error repairing map: Input/output error (5)

Any suggestions?

@sergeydgr8
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So I figured out how to unbrick my drive, but it required loading up a VM of Windows in Parallels and directing USB over to it. Windows fixed the drive and loaded it up just fine, and after the job, it loaded up in macOS right after.

@lilyhara
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My external hard disk partition (disk2s1) can't be mounted and grayed out in disk utility.The error I get when I run
sudo fsck_exfat -d disk2s1 is

`Password:
Opening /dev/rdisk2s1
** Checking volume.
** Checking main boot region.
1953519616 total sectors; 512 bytes per sector
FAT starts at sector 2048; size 61440 sectors
7630688 clusters starting at sector 63488; 131072 bytes per cluster
Root directory starts at cluster 11
Read offset = 0x000000100000 length = 0x001000
** Checking system files.
Read offset = 0x000002020000 length = 0x020000
fsck_exfat: Couldn't read 131072 bytes at offset 33685504: Input/output error
No upper case translation table was found.
CONTINUE? Yes
Using default upper case translation table.
No main bitmap was found.
CONTINUE? Yes
**** Checking file system hierarchy.**
Directory /
Read offset = 0x000002020000 length = 0x020000
fsck_exfat: Couldn't read 131072 bytes at offset 33685504: Input/output error
Upper case translation table must be replaced.
Replace? Yes
Read offset = 0x000001f00000 length = 0x020000
fsck_exfat: Couldn't read 131072 bytes at offset 32505856: Input/output error
The volume could not be verified completely.

The disk utility gives me this error when I run first aid on the unmounted partition.

Running First Aid on “” (disk2s1)
Repairing file system.
Volume is already unmounted.
Performing fsck_exfat -y -x /dev/rdisk2s1
Checking volume.
Checking main boot region.
Checking system files.
No uppercase translation table was found.
Using default uppercase translation table.
No main bitmap was found.
Checking file system hierarchy.
Uppercase translation table must be replaced.`

Does anyone have same experience? Any suggestions? Thank you in advance :)

@minksW
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minksW commented Jul 5, 2023

halp pls

@berkeozkir
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I have been dealing with this error for almost 6 years now. My drives are big 6TB - 8TB I cannot use FAT32 for that reason I have to use exFat to make my drives compatible with both windows and Mac. The drives always mount on my windows machine but on Mac it randomly mounts. Apple needs to fix this. When I urgently have a need to access my data sometimes I cannot mount it on Mac so I have to use windows as a middle man or use virtual machine like parallels. It's interesting the Mac cannot mount but VM running on it can mount it. Anyways thanks for your help. It sucks that I always have to come here to check solutions because I forget the command prompts.

@dejanovicnenad
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dejanovicnenad commented Aug 16, 2023 •
edited
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@krsnk — Did you try from the Terminal:

diskutil list

The volumes listed should show your disk ("rdisk2s1") and possibly its partitions.

Then, copy paste this (replace "disk2") in the example below with your disk's or partition's name (of course, remove "(but your disk)").

sudo ps -ax | grep disk2 (but your disk)

you should get the process number keeping your disk busy:

13699 ?? 11:52.83 /System/Library/Filesystems/hfs.fs/Contents/Resources/./fsck_hfs -y /dev/disk2s2

Then execute:

sudo kill 13699

In the example above, "13699" refers to the process currently busy, but it should be a different number on your machine.

After killing the process, the drive should mount, with a Finder's warning.

This worked for me, but I had to use sudo kill -9 {PID} to kill the process successfully.

@Dax-87
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Dax-87 commented Nov 11, 2023

Thank you so much you saved my life.
I had 3 HDDs that failed at the same time.
With this guide I solved it.

@saxondigital
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Been fixing the OSX exFAT corruption using MS Windows 'chkdsk /r /f'

So far, has worked every time, but can take a couple hours on spinning disks.
The problem goes back many years (at least with OSX 10.11 - 10.14).

Next time (won't be long), I will try the Mac based method explained here.

@att11
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att11 commented Jan 2, 2024

Hi @scottopell, thanks, I tried this method, the result was:
** Checking volume.
** Checking main boot region.
fsck_exfat: Invalid jump or signature
Main boot region is invalid. Trying alternate boot region.
** Checking alternate boot region.
fsck_exfat: Invalid jump or signature
Alternate boot region is invalid.
** The volume could not be verified completely.

Any idea what might be wrong, how could I fix this? Thanks in advance, att

@Titencer
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Titencer commented Jan 6, 2024

  1. Use diskutil list to find the right drive id.
  2. You want the id under the IDENTIFIER column, it should look like disk1s1
  3. Run 'sudo fsck_exfat -d '. eg 'sudo fsck_exfat -d disk1s3'
  4. -d is debug so you'll see all your files output as they're processed.
  5. Answer YES if it gives you the prompt Main boot region needs to be updated. Yes/No?
  6. Open Disk Utility and you should be able to repair here successfully.

Hey! Did this after getting my 6tb ExFat drive to at least be view only. Prior to this, I tried sudo pkill -f fsck but that did not allow the drive to mount, nor be repaired through First Aid. Since running the above command, it's been going files for a couple hours now. Is this supposed to take a super long time? Worried it's just stuck in fsck_exfat again. It's view only now but I won't be able to get another hard drive for a little bit.

@Titencer
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Titencer commented Jan 6, 2024

  1. Use diskutil list to find the right drive id.
  2. You want the id under the IDENTIFIER column, it should look like disk1s1
  3. Run 'sudo fsck_exfat -d '. eg 'sudo fsck_exfat -d disk1s3'
  4. -d is debug so you'll see all your files output as they're processed.
  5. Answer YES if it gives you the prompt Main boot region needs to be updated. Yes/No?
  6. Open Disk Utility and you should be able to repair here successfully.

Hey! Did this after getting my 6tb ExFat drive to at least be view only. Prior to this, I tried sudo pkill -f fsck but that did not allow the drive to mount, nor be repaired through First Aid. Since running the above command, it's been going files for a couple hours now. Is this supposed to take a super long time? Worried it's just stuck in fsck_exfat again. It's view only now but I won't be able to get another hard drive for a little bit.

Adding to this - I'm running macOS Ventura 13.6.1 (22G313)

@ty-hei
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ty-hei commented Jan 30, 2024

Hi @scottopell, thanks, I tried this method, the result was: ** Checking volume. ** Checking main boot region. fsck_exfat: Invalid jump or signature Main boot region is invalid. Trying alternate boot region. ** Checking alternate boot region. fsck_exfat: Invalid jump or signature Alternate boot region is invalid. ** The volume could not be verified completely.

Any idea what might be wrong, how could I fix this? Thanks in advance, att

My solution is link the disk to a Windows computer, it repaired the disk auto. Unbelievable.

@livingperson
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Also had issues mentioned above. My solution was to connect it to Windows, and do the following:

Run Disk Error Checking

  1. Plug in your external hard disk.
  2. Open File Explorer by pressing the Windows keys button + E.
  3. Go to This PC.
  4. Right-click your external hard disk under Devices and drives.
  5. Select Properties
  6. Go to Tools tab.
  7. Under Error checking, click Check.
  8. If prompted, click Yes or enter the administrator password.
  9. Click Scan drive > Repair drive.
  10. Wait for the process to finish.
  11. The scanning process may take a while depending on the size of your external hard disk and the specifications of your PC.

@suebphattana
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Also had issues mentioned above. My solution was to connect it to Windows, and do the following:

Run Disk Error Checking

  1. Plug in your external hard disk.
  2. Open File Explorer by pressing the Windows keys button + E.
  3. Go to This PC.
  4. Right-click your external hard disk under Devices and drives.
  5. Select Properties
  6. Go to Tools tab.
  7. Under Error checking, click Check.
  8. If prompted, click Yes or enter the administrator password.
  9. Click Scan drive > Repair drive.
  10. Wait for the process to finish.
  11. The scanning process may take a while depending on the size of your external hard disk and the specifications of your PC.

Saved my life! thanks!

@ibassman
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ibassman commented Jun 5, 2024

So I figured out how to unbrick my drive, but it required loading up a VM of Windows in Parallels and directing USB over to it. Windows fixed the drive and loaded it up just fine, and after the job, it loaded up in macOS right after.

Hey. My external hard disk stopped working while I was switching between mac and parallel windows vm.
Can you please share how you fixed your drive? (If it doesn't involve a format)
Thanks

@TechGenius12
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Hey yall, from the far future! It would help if you added this to the OG posting.

If you're unable to kill the process via sudo command in terminal, open "Activity Monitor", search up "fsck_exfat" , and force quit the process.

The debugging process will work after you insert the "sudo fsck_exfat -d

@ellielo
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ellielo commented Sep 2, 2024 •
edited
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This issue sounds familiar to me. It’s happened to me a couple of times where my external hard drive access denied and each time, the solution ended up being different. It can be super frustrating! I recently found this blog https://www.handyrecovery.com/external-hard-drive-access-denied/ which covers all sorts of fixes and tips

@Vito89
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Vito89 commented Nov 16, 2024

Thank's a lot! It has works for me at earlier than 15.0 Sequoia version MacBooks. I have tried few laptops and after that got success at Rethina iMac Monterey version.

@theharshpat
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sudo fsck_exfat -d . eg sudo fsck_exfat -d disk1s3

This worked, thanks a lot. I had to answer "YES" a few times to allow it to fix issues. Keep an eye on the output!

@ellielo
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ellielo commented Nov 24, 2024 •
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Great thread! Thanks to everyone for the input—I’ve learned a lot from this discussion. I just wanted to add my two cents and recommend this article about the external hard drive access denied issue that I found on the blog: https://blog.7datarecovery.com/external-hard-drive-access-denied/. It provides some solid solutions and troubleshooting steps for this specific problem. If you're having trouble accessing your external drive, this guide might be just what you need. The instructions are clear, and it covers different methods to regain access. Hopefully, it’ll be helpful for anyone experiencing the same issue

@phuongnd08
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Life saver! A note is that you should eject the disk in Disk Utilities so that fsck_exfat is able to repair the disk.

@Bougakov
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yes | sudo fsck_exfat -d <id from above> would save you from watching the check to run for eternity. A yes command answers y to every prompt. Since fsck_exfat is your last hope you don't have other options so why bother examining its decisions?

@markste-in
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I have tried your suggestions @scottopell but it has not worked for me. What should I do next?

$ sudo fsck_exfat /dev/disk2s2
Password:
** Checking volume.
** Checking main boot region.
fsck_exfat: Could not read boot region
** The volume  could not be verified completely.
$ sudo fsck_exfat -d disk2s2
Password:
Opening /dev/rdisk2s2
** Checking volume.
** Checking main boot region.
fsck_exfat: Could not read boot region
** The volume  could not be verified completely.

I got the same error and struggled quite a bit with it. I almost gave up but the solution is not that hard. You actually 'just' need to overwrite the the dirty flag (at least in my case). I wrote a little script here

https://github.com/markste-in/exfat-repair

@layerstech
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image image

Running First Aid on “layers” (disk4s1)

Checking file system and repairing if necessary and if possible.
Volume is already unmounted.
Performing fsck_exfat -y -x /dev/rdisk4s1
Checking volume.
Checking main boot region.
The volume could not be verified completely.
File system check exit code is 1.
Restoring the original state found as unmounted.
File system verify or repair failed. : (-69845)

Operation failed…

Pls help to solve this error, as not able to find SSD in fider......

@kkang386
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kkang386 commented Mar 26, 2025 •
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Thanks for @cocotyty's post in 2022.
This saved my exfat drive from an inadvertent ejection:
brew install gdisk
sudo gdisk /dev/diskxyz
w

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