I’m having an issue with my Mac OS X installation. When I start up the system I see a circle with a line through it. I reboot into Recovery Mode by pressing Cmd-R and open Disk Utility. It shows the Macintosh HD partition (/dev/disk0s2) as being “unformatted”. I open Terminal, run fsck_hfs, and it says Macintosh HD is OK.

I can also successfully mount and unmount Macintosh HD with no signs of corruption. I have two questions.

Why does it have a circle with a line through it when I try to boot?

Why does it say unformatted when it clearly isn’t?

Edit 1:

I have MacOS High Sierra. Can’t update further. Not sure what version because I can’t get on to check.

diskutil list:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI NO NAME                 2.3 GB     disk0s1
   2:          Apple_CoreStorage                         448.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:           Linux Filesystem                         48.9 GB    disk0s4

Edit 2: Oh my goodness! I completely forgot to say that I set up a dual boot of MacOS and Pop!_OS. That's what the Linux Filesystem is. I have opened GParted on Pop!_OS. This is what I see. It correctly Identifies /dev/sda2 (/dev/disk0s2) as HFS+. Disk Utility identifies it as CoreStorage for some reason. GParted

Edit 3:

diskutil cs list:

No CoreStorage logical volume groups found
  • Please tell us what version of macOS and try to capture and report the output of diskutil list.
    – Gilby
    Aug 8, 2021 at 2:50
  • @Gilby answer away. Aug 8, 2021 at 13:22
  • Can you add the result of diskutil cs list?
    – user415185
    Aug 8, 2021 at 16:05
  • Was that all of diskutil list? And please do as @Jean_JD requests.
    – Gilby
    Aug 9, 2021 at 2:29
  • 1
    I suppose the partition type in the GPT is 53746F72-6167-11AA-AA11-00306543ECAC and is suppose to be 48465300-0000-11AA-AA11-00306543ECAC. Aug 9, 2021 at 12:26

2 Answers 2


Thank you to @David Anderson for the solution.

I think the problem was that when I was modifying my partitions to make space for Pop!_OS, GParted changed the GPT partition type. I didn't notice at the time as GParted identifies partitions by their filesystem signature as opposed to the partition type. I used gdisk on Pop!_OS to change the partition type from AF05 to AF00 and it boots properly. Yay!

  • I think what might have confused Mac users is when you stated you were able to "mount and unmount Macintosh HD". Personally, I first assumed you used the diskutil command to mount, but you must have used the mount command instead. Aug 9, 2021 at 13:08
  • @DavidAnderson yes, I just did mkdir "/Volumes/Macintosh HD" && mount_hfs /dev/disk0s2 "/Volumes/Macintosh HD" from the terminal in recovery mode. Aug 9, 2021 at 14:45

(too long for a comment)

There is something wrong with your output of diskutil list.

Here is a typical output for a High Sierra system with an HDD:

/dev/disk0 (internal, physical): 
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *250.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            249.2 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

I wonder why you get Apple_CoreStorage instead of Apple_HFS.

Please post the complete output of diskutil list.

  • Might get CoreStorage because it was a FileVault volume. Might get CoreStorage because it is an APFS container volume. Aug 8, 2021 at 16:08
  • sorry, i didnt bother to open safari on the recovery system so I typed in what thought was important on my phone. I have now pasted the full output. Aug 8, 2021 at 23:31

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