I bought a new HDD, formatted as exFAT with mac. I moved files from my laptop to the HDD (moved, I mean, I also deleted them). It happened with a directory it got stucked. I quit the process of copying that directory. I tried to trash and erase trash. I could not erase it. I tried eject from Finder. It could not. I unplugged - when there were no process active.

I tried to plug, and could not mount. I discover apple run fsck automatically. I kill the process, used diskutil to mount the volume, unmount and eject.

I tried to plug and mount and again. Now the volume is mounted, but Read only. S.M.A.R.T. not verified.

So I launch fsck - I don't know when it will finish, there are (estimated) about million files, HDD is 4T.

I m confident disk is ok, since brand new.

Please advice on how get rid of read-only and steps to mount exFAT external HDD properly in mac, want to prevent automatic fsck - also because fsck is taking forever, and not sure it could repare anything if in read-only mode. FSCK is stuck at checking system hierarchy:

    diskutil list

   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            499.4 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *4.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:       Microsoft Basic Data myHDD                 4.0 TB     disk1s2

sudo fsck_exfat /dev/disk1s2
fsck_exfat: Opened /dev/rdisk1s2 read-only
** Checking volume.
** Checking main boot region.
** Checking system files.
** Volume name is luigi4T.
** Checking upper case translation table.
** Checking file system hierarchy.

Mac OS 1.9.5

2 Answers 2


If your exfat drive shows up as read-only, then all you need to do is unmount the drive and then use the "mount_exfat" utility to mount the drive. Once you do this, and right click on the drive → "Get Info" will tell that you have custom access to the drive, instead of "read-only". Here are the steps:

  1. Open the terminal on your mac.

  2. Type diskutil list and you will get a listing like this:

    /dev/disk0 (internal, physical):    #:                       TYPE NAME SIZE       IDENTIFIER    0:      GUID_partition_scheme                
    *500.3 GB   disk0    1:                        EFI EFI                     209.7 MB   disk0s1    2:                 Apple_APFS Container disk1         500.1 GB   disk0s2
    /dev/disk1 (synthesized):    #:                       TYPE NAME        SIZE       IDENTIFIER    0:      APFS Container Scheme -              
    +500.1 GB   disk1
                                 Physical Store disk0s2    1:                APFS Volume Untitled - Data         407.2 GB   disk1s1    2:           APFS Volume Preboot                 82.4 MB    disk1s2    3:           APFS Volume Recovery                528.5 MB   disk1s3    4:           APFS Volume VM                      3.2 GB     disk1s4    5:           APFS Volume Untitled                10.7 GB    disk1s5
    /dev/disk2 (external, physical):    #:                       TYPE NAME SIZE       IDENTIFIER    0:      GUID_partition_scheme                
    *5.0 TB     disk2    1:                        EFI EFI                     209.7 MB   disk2s1    2:       Microsoft Basic Data Backup Plus             5.0 TB     disk2s2
  3. In the listing above, we notice that /dev/disk2s2 is our external drive. Unmount the drive by runningsudo umount /dev/disk2s2`.

  4. Now create a directory in in /Volumes by running sudo mkdir -p /Volumes/<name of your volume>

  5. Mount the hard drive to this directory your created by running sudo mount_exfat /dev/disk2s2 /Volumes/<name of your volume>.

Once this is done, you should be able to create new folders and write to your drive.

  • Please fix the formatting of your diskutil list output.
    – klanomath
    Dec 24, 2019 at 11:21
  • Thank you so much, it worked. Nov 16, 2020 at 11:41
  • This worked so well. Thanks a lot.
    – dpak23in
    Dec 26, 2020 at 17:01

Being mounted in read-only mode is necessary for fsck (which is short for File System ChecK) to run; it ensures that no processes other than fsck are tampering with the data on the disk.

If a disk is mounting read-only it's because the operating system detected a problem with it which requires repair. If you have access to a Linux or Windows machine they may be able to run the disk repair process more quickly, but regardless, something needs to go through the whole disk and repair whatever damage may have occurred by the unclean disconnection.

Simply waiting for there to be "no processes" is also insufficient to ensure that a disk is safe for removal; the operating system takes some time to flush out its write caches and other performance-enhancing processes that allow you to get more work done while the actual disk operations happen in the background. It's possible that the files were not fully transferred; hopefully you have backups of them (which is a good policy to have in any case).

  • My purpose was indeed making a backup on the HDD. I deleted already some files. fsck result:Read offset = 0x0000051c0000 length = 0x040000 0 clusters were marked used, but not referenced 0 clusters were marked used and CLUST_BAD 0 clusters were marked free, but referenced (S,"Rechecking main boot region.",0) (S,"Rechecking alternate boot region.",0) (S,"The volume %1$@ appears to be OK.",1) I ejected from diskutil, re-plugged the HDD: ps aux | grep disk1 mac automatically re-launches /System/Library/Filesystems/exfat.fs/Contents/Resources/./fsck_exfat -y /dev/rdisk1s2
    – user305883
    Mar 21, 2019 at 8:34

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