Disk utility says partition is unformatted, Fsck says Macintosh HD is OK

Question

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.

Edit 3:

diskutil cs list:

No CoreStorage logical volume groups found

Answer 1

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!

Answer 2

(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.