I am trying to mount an external HD with exFAT, but apparently the latest unmount was non-successful, and now the disk requires an automatic fsck. When macos tries to perform the fsck, this happens

Process:               fsck_exfat [47683]
Path:                  /System/Library/Filesystems/exfat.fs/Contents/Resources/fsck_exfat
Identifier:            fsck_exfat
Version:               90.200.1
Code Type:             X86-64 (Native)
Parent Process:        diskarbitrationd [66]
Responsible:           fsck_exfat [47683]
User ID:               0

Date/Time:             2019-04-05 00:13:11.857 +0100
OS Version:            Mac OS X 10.14.3 (18D109)
Report Version:        12
Bridge OS Version:     3.3 (16P3133)
Anonymous UUID:        972E6B24-EE1F-B5A0-2545-E9EE3AE52D78

Time Awake Since Boot: 980000 seconds

System Integrity Protection: enabled

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_CRASH (SIGABRT)
Exception Codes:       0x0000000000000000, 0x0000000000000000
Exception Note:        EXC_CORPSE_NOTIFY

Application Specific Information:
dyld3 mode
Assertion failed: (result->data == NULL), function fsck_exfat_cache_recycle, file /BuildRoot/Library/Caches/com.apple.xbs/Sources/exfat/exfat-90.200.1/fsck/fsck_exfat_cache.c, line 248.

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libsystem_kernel.dylib          0x00007fff6ff9d23e __pthread_kill + 10
1   libsystem_pthread.dylib         0x00007fff70053c1c pthread_kill + 285
2   libsystem_c.dylib               0x00007fff6ff061c9 abort + 127
3   libsystem_c.dylib               0x00007fff6fece868 __assert_rtn + 320
4   fsck_exfat                      0x00000001099961a1 0x10998e000 + 33185
5   fsck_exfat                      0x000000010999634e 0x10998e000 + 33614
6   fsck_exfat                      0x00000001099953ff 0x10998e000 + 29695
7   fsck_exfat                      0x0000000109993068 0x10998e000 + 20584
8   fsck_exfat                      0x0000000109993461 0x10998e000 + 21601
9   libdyld.dylib                   0x00007fff6fe5ded9 start + 1

Thread 1:
0   libsystem_pthread.dylib         0x00007fff700503f8 start_wqthread + 0
1   ???                             0x0000000054485244 0 + 1414025796

Thread 0 crashed with X86 Thread State (64-bit):
  rax: 0x0000000000000000  rbx: 0x00000001146785c0  rcx: 0x00007ffee6271998  rdx: 0x0000000000000000
  rdi: 0x0000000000000507  rsi: 0x0000000000000006  rbp: 0x00007ffee62719d0  rsp: 0x00007ffee6271998
   r8: 0x00000000000000f8   r9: 0xcccccccccccccccd  r10: 0x0000000000000000  r11: 0x0000000000000206
  r12: 0x0000000000000507  r13: 0x0000000109ac9000  r14: 0x0000000000000006  r15: 0x000000000000002d
  rip: 0x00007fff6ff9d23e  rfl: 0x0000000000000206  cr2: 0x00007fffa2c37188

Logical CPU:     0
Error Code:      0x02000148
Trap Number:     133

Binary Images:
       0x10998e000 -        0x109999fff  fsck_exfat (90.200.1) <5040465B-D4D0-3486-8BC0-51662BCFAD1D> /System/Library/Filesystems/exfat.fs/Contents/Resources/fsck_exfat
       0x1145c2000 -        0x114640a87  dyld (655.1) <3EBA447F-A546-366B-B302-8DC3B21A3E30> /usr/lib/dyld
    0x7fff42bd5000 -     0x7fff43022fef  com.apple.CoreFoundation (6.9 - 1562) <02A2C178-9FF6-385C-A9C5-7F4FC9D66311> /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation
    0x7fff6cf1f000 -     0x7fff6cf20ff7  libDiagnosticMessagesClient.dylib (107) <15210AC0-61F9-3F9D-A159-A009F62EB537> /usr/lib/libDiagnosticMessagesClient.dylib
    0x7fff6d2d1000 -     0x7fff6d2d2ffb  libSystem.B.dylib (1252.200.5) <C6201660-5E17-397D-BA21-C503420CD706> /usr/lib/libSystem.B.dylib
    0x7fff6d52b000 -     0x7fff6d582ff7  libc++.1.dylib (400.9.4) <B260AC33-EB9A-30C6-8746-D011B3B02B08> /usr/lib/libc++.1.dylib
    0x7fff6d583000 -     0x7fff6d598fff  libc++abi.dylib (400.17) <446F4748-8A89-3D2E-AE1C-27EEBE93A8AB> /usr/lib/libc++abi.dylib
    0x7fff6e1e7000 -     0x7fff6e44affb  libicucore.A.dylib (62109.0.1) <FEB89BD3-79C4-3208-A754-7E6BC4D38548> /usr/lib/libicucore.A.dylib
    0x7fff6ed79000 -     0x7fff6f4fffe7  libobjc.A.dylib (750.1) <804715F4-F52D-34D0-8FEC-A25DC08513C3> /usr/lib/libobjc.A.dylib
    0x7fff6fc5c000 -     0x7fff6fc6effb  libz.1.dylib (70.200.4) <15F7B40A-424C-33BB-BF2C-7E8195128B78> /usr/lib/libz.1.dylib
    0x7fff6fcdf000 -     0x7fff6fce3ff3  libcache.dylib (81) <704331AC-E43D-343A-8C24-39201142AF27> /usr/lib/system/libcache.dylib
    0x7fff6fce4000 -     0x7fff6fceeff3  libcommonCrypto.dylib (60118.220.1) <9C865644-EE9A-3662-AB77-7C8A5E561784> /usr/lib/system/libcommonCrypto.dylib
    0x7fff6fcef000 -     0x7fff6fcf6fff  libcompiler_rt.dylib (63.4) <817772E3-E836-3FFD-A39B-BDCD1C357221> /usr/lib/system/libcompiler_rt.dylib
    0x7fff6fcf7000 -     0x7fff6fd00ff3  libcopyfile.dylib (146.200.3) <5C5C4F35-DAB7-3CF1-940F-F47192AB8289> /usr/lib/system/libcopyfile.dylib
    0x7fff6fd01000 -     0x7fff6fd85fdf  libcorecrypto.dylib (602.230.1) <C78D1A87-5543-3561-BEB4-3B480BA94ECB> /usr/lib/system/libcorecrypto.dylib
    0x7fff6fe0c000 -     0x7fff6fe46ff7  libdispatch.dylib (1008.220.2) <2FDB1401-5119-3DF0-91F5-F4E105F00CD7> /usr/lib/system/libdispatch.dylib
    0x7fff6fe47000 -     0x7fff6fe76ff3  libdyld.dylib (655.1) <90C801E7-5D05-37A8-810C-B58E8C53953A> /usr/lib/system/libdyld.dylib
    0x7fff6fe77000 -     0x7fff6fe77ffb  libkeymgr.dylib (30) <A4EFD9A4-2EF3-3E18-B325-F527E3821939> /usr/lib/system/libkeymgr.dylib
    0x7fff6fe85000 -     0x7fff6fe85ff7  liblaunch.dylib (1336.240.2) <D5F0014D-CF46-3B04-9DE0-A1466DA14A2C> /usr/lib/system/liblaunch.dylib
    0x7fff6fe86000 -     0x7fff6fe8bfff  libmacho.dylib (921) <6ADB99F3-D142-3A0A-B3CE-031354766ACC> /usr/lib/system/libmacho.dylib
    0x7fff6fe8c000 -     0x7fff6fe8effb  libquarantine.dylib (86.220.1) <58524FD7-63C5-38E0-9D90-845A79551C14> /usr/lib/system/libquarantine.dylib
    0x7fff6fe8f000 -     0x7fff6fe90ff3  libremovefile.dylib (45.200.2) <BA53CA8A-9974-3A43-9265-B110B1AE470F> /usr/lib/system/libremovefile.dylib
    0x7fff6fe91000 -     0x7fff6fea8ff3  libsystem_asl.dylib (356.200.4) <33C62769-1242-3BC1-9459-13CBCDECC7FE> /usr/lib/system/libsystem_asl.dylib
    0x7fff6fea9000 -     0x7fff6fea9fff  libsystem_blocks.dylib (73) <152EDADF-7D94-35F2-89B7-E66DCD945BBA> /usr/lib/system/libsystem_blocks.dylib
    0x7fff6feaa000 -     0x7fff6ff32fff  libsystem_c.dylib (1272.200.26) <D6C701A2-9F17-308D-B6AC-9E17EF31B7DF> /usr/lib/system/libsystem_c.dylib
    0x7fff6ff33000 -     0x7fff6ff36ff7  libsystem_configuration.dylib (963.200.27) <94898525-ECC8-3CC9-B312-CBEAAC305E32> /usr/lib/system/libsystem_configuration.dylib
    0x7fff6ff37000 -     0x7fff6ff3aff7  libsystem_coreservices.dylib (66) <10818C17-70E1-328E-A3E3-C3EB81AEC590> /usr/lib/system/libsystem_coreservices.dylib
    0x7fff6ff3b000 -     0x7fff6ff41ffb  libsystem_darwin.dylib (1272.200.26) <07468CF7-982F-37C4-83D0-D5E602A683AA> /usr/lib/system/libsystem_darwin.dylib
    0x7fff6ff42000 -     0x7fff6ff48ff7  libsystem_dnssd.dylib (878.240.1) <5FEA5E1E-E80F-3616-AD33-8E936D61F31A> /usr/lib/system/libsystem_dnssd.dylib
    0x7fff6ff49000 -     0x7fff6ff95ff3  libsystem_info.dylib (517.200.9) <54B65F21-2E93-3579-9B72-6637A03245D9> /usr/lib/system/libsystem_info.dylib
    0x7fff6ff96000 -     0x7fff6ffbeff7  libsystem_kernel.dylib (4903.241.1) <CA10BC3A-5B09-32CE-B74F-BAD01755AA37> /usr/lib/system/libsystem_kernel.dylib
    0x7fff6ffbf000 -     0x7fff7000aff7  libsystem_m.dylib (3158.200.7) <AF25F8E8-194C-314F-A2D3-A424853EE796> /usr/lib/system/libsystem_m.dylib
    0x7fff7000b000 -     0x7fff7002fff7  libsystem_malloc.dylib (166.220.1) <4777DC06-F9C6-356E-82AB-86A1C6D62F3A> /usr/lib/system/libsystem_malloc.dylib
    0x7fff70030000 -     0x7fff7003bff3  libsystem_networkextension.dylib (767.240.1) <4DB0D4A2-83E7-3638-AAA0-39CECD5C25F8> /usr/lib/system/libsystem_networkextension.dylib
    0x7fff7003c000 -     0x7fff70043fff  libsystem_notify.dylib (172.200.21) <65B3061D-41D7-3485-B217-A861E05AD50B> /usr/lib/system/libsystem_notify.dylib
    0x7fff70044000 -     0x7fff7004dfef  libsystem_platform.dylib (177.200.16) <83DED753-51EC-3B8C-A98D-883A5184086B> /usr/lib/system/libsystem_platform.dylib
    0x7fff7004e000 -     0x7fff70058fff  libsystem_pthread.dylib (330.230.1) <80CC5992-823E-327E-BB6E-9D4568B84161> /usr/lib/system/libsystem_pthread.dylib
    0x7fff70059000 -     0x7fff7005cff7  libsystem_sandbox.dylib (851.230.3) <D6469A17-C13C-3538-A300-D6517BB7F249> /usr/lib/system/libsystem_sandbox.dylib
    0x7fff7005d000 -     0x7fff7005fff3  libsystem_secinit.dylib (30.220.1) <5964B6D2-19D4-3CF9-BDBC-4EB1D42348F1> /usr/lib/system/libsystem_secinit.dylib
    0x7fff70060000 -     0x7fff70067ff7  libsystem_symptoms.dylib (820.237.2) <487E1794-4C6E-3B1B-9C55-95B1A5FF9B90> /usr/lib/system/libsystem_symptoms.dylib
    0x7fff70068000 -     0x7fff7007dff7  libsystem_trace.dylib (906.220.1) <4D4BA88A-FA32-379D-8860-33838723B35F> /usr/lib/system/libsystem_trace.dylib
    0x7fff7007f000 -     0x7fff70084ffb  libunwind.dylib (35.4) <EF1A77FD-A86B-39F5-ABEA-6100AB23583A> /usr/lib/system/libunwind.dylib
    0x7fff70085000 -     0x7fff700b5fff  libxpc.dylib (1336.240.2) <EE0CDA53-6FF9-3B4E-A571-335A5FF6B6F4> /usr/lib/system/libxpc.dylib

External Modification Summary:
  Calls made by other processes targeting this process:
    task_for_pid: 0
    thread_create: 0
    thread_set_state: 0
  Calls made by this process:
    task_for_pid: 0
    thread_create: 0
    thread_set_state: 0
  Calls made by all processes on this machine:
    task_for_pid: 602965
    thread_create: 0
    thread_set_state: 0

VM Region Summary:
ReadOnly portion of Libraries: Total=234.6M resident=0K(0%) swapped_out_or_unallocated=234.6M(100%)
Writable regions: Total=356.0M written=0K(0%) resident=0K(0%) swapped_out=0K(0%) unallocated=356.0M(100%)

                                VIRTUAL   REGION 
REGION TYPE                        SIZE    COUNT (non-coalesced) 
===========                     =======  ======= 
Dispatch continuations            24.0M        2 
Kernel Alloc Once                    8K        2 
MALLOC                           276.2M       23 
MALLOC guard page                   16K        5 
MALLOC_LARGE (reserved)           46.3M        2         reserved VM address space (unallocated)
STACK GUARD                       56.0M        3 
Stack                             8712K        3 
VM_ALLOCATE                          4K        2 
__DATA                            4664K       44 
__LINKEDIT                       216.1M        4 
__TEXT                            18.5M       44 
__UNICODE                          564K        2 
shared memory                        8K        3 
===========                     =======  ======= 
TOTAL                            650.8M      126 
TOTAL, minus reserved VM space   604.5M      126 

It brings the whole system down with it. The mac reboots.

Is this a known issue? I could not find anything googling. Do you have a workaround for it?

  • 1
    Do you have software that can read and write extFS installed on your Mac (like Paragon)? extFS ist not supported by macOS out of the box and the Finder thinks the drive is formatted as exFAT (see the process name in the first line of the error message: it's fsck_exfat!). You would probably be better off checking and repairing your extFS drive on Linux instead of macOS. If you don't have a Linux computer around, you could always create a VM (for instance with VirtualBox) and install your preferred Linux distro on it. – jaume Apr 12 at 10:28
  • 1
    @jaume I am incorrect in the question. I meant exFAT, not extfs. The filesystem is exFAT (formatted under windows, and worked correctly under macos until a few days ago). Probably due to incorrect unmount, mac now tries to fsck it and crashes. – Stefano Borini Apr 12 at 13:24

This is not a problem with the drive. Newly-formatted drives get the same fsck_exfat error. It is a problem with fsck_exfat on versions of Mac OS X newer than Snow Leopard.

As man fsck_exfat says:

The fsck_exfat utility first appeared in Mac OS X 10.6.3.

I don't know how you can bypass the required automatic fsck in macos 10.14.4. It is fsck_exfat -q <disk> that quickly checks to see if the volume was "cleanly unmounted". Perhaps that is being automatically run. I don't know if booting into safe mode would stop the automatic check.

Maybe try downgrading to the version of fsck_exfat that comes with Snow Leopard and see if it still reports an error with fsck_exfat_cache.c. which fsck_exfat reports that it is located at /sbin/fsck_exfat.

If you are concerned about the external HD, use fsck_exfat that comes with an updated version of Mac OS X Snow Leopard (Mac OS X 10.6.8), or try a free version of Linux as jaume commented. You can buy a Snow Leopard retail disk. With CentOS, install the exfat-utils and fuse-exfat EPEL packages.

This is the kind of output you should be receiving:

$ sudo fsck_exfat /dev/disk3s1
fsck_exfat: Opened /dev/rdisk3s1 read-only
** Checking volume.
** Checking main boot region.
** Checking system files.
** Volume name is [volume name].
** Checking upper case translation table.
** Checking file system hierarchy.
** Checking active bitmap.
** Rechecking main boot region.
** Rechecking alternate boot region.
Mark volume clean? n
** The volume [volume name] appears to be OK.

Read Using exFAT as a common filesystem at Galaxy Verge.


You seem to have hit a bug in the exFAT code.

I would advise taking the external drive to a different computer, such as for example a Windows PC. Run chkdisk (or fsck on Linux), and the file system back in shape.

Afterwards you should be able to continue using the drive on your Mac.

If not, I would suggest using a different computer to copy away your files from the drive, and then reformat it, before copying your files back.

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