I have an external hard drive that has two partitions and one of them is not being mounted. The one that is not being mounted has data I would like to recover. Right before the problem I had installed OS X Mojave on it but after once booting into it, on a reboot I just got a blank screen. So I restarted the mac and discovered that the partition itself cannot be mounted.
I have gone through a fair bit of article on this forum and elsewhere on this and I am going to give the information I think may be relevant. The disk in question is /dev/disk2
The output of diskutil list is:
/dev/disk0 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *251.0 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_CoreStorage Macintosh HD 250.1 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3
/dev/disk1 (internal, virtual):
#: TYPE NAME SIZE IDENTIFIER
0: Apple_HFS Macintosh HD +249.8 GB disk1
Logical Volume on disk0s2
21851A15-0785-48A0-A736-0FEF2E06952B
Unencrypted
/dev/disk2 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk2
1: EFI EFI 209.7 MB disk2s1
2: Apple_HFS Untitled 1 300.0 GB disk2s2
3: 7C3457EF-0000-11AA-AA11-00306543ECAC 699.8 GB disk2s3
The output of sudo gpt -r show disk2 is
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 585937504 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
586347144 262144
586609288 1366848848 3 GPT part - 7C3457EF-0000-11AA-AA11-00306543ECAC
1953458136 7
1953458143 32 Sec GPT table
1953458175 1 Sec GPT header
The output of sudo hexdump -Cv -n 512 /dev/disk2s3 is
00000000 c0 eb e0 54 ab 54 c5 33 01 00 00 00 00 00 00 00 |...T.T.3........|
00000010 ca 02 00 00 00 00 00 00 01 00 00 80 00 00 00 00 |................|
00000020 4e 58 53 42 00 10 00 00 aa 0e 2f 0a 00 00 00 00 |NXSB....../.....|
00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000040 02 00 00 00 00 00 00 00 05 69 77 e5 1b 75 49 0e |.........iw..uI.|
00000050 81 7c 14 7b c7 2c e5 35 a5 e2 00 00 00 00 00 00 |.|.{.,.5........|
00000060 cb 02 00 00 00 00 00 00 18 01 00 00 44 6c 00 00 |............Dl..|
00000070 6d 3a 09 00 00 00 00 00 8e 90 08 00 00 00 00 00 |m:..............|
00000080 21 00 00 00 01 38 00 00 1f 00 00 00 02 00 00 00 |!....8..........|
00000090 da 37 00 00 27 00 00 00 39 3e 00 00 00 00 00 00 |.7..'...9>......|
000000a0 05 30 10 00 00 00 00 00 01 04 00 00 00 00 00 00 |.0..............|
000000b0 00 00 00 00 64 00 00 00 03 04 00 00 00 00 00 00 |....d...........|
000000c0 06 04 00 00 00 00 00 00 31 3e 00 00 00 00 00 00 |........1>......|
000000d0 2c dd 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |,...............|
000000e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000100 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000120 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000130 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000140 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000150 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000160 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000170 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000180 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000190 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000200
I was largely following what sounded to be a similar problem but in my case I find that the container is APFS. So that didn't help.
Furthermore, I tried TestDisk based on but it gave me the wrong starting and ending sectors (which I realized among other ways by hexdump).
To be honest, at this point I do not even see how to see there is a problem from the diagnostics above except that disk2s3 does not mount.
One more point, I looked at the disk through Steller Data Recovery Professional and find the files I am interested in. However, (a) I do not want to pay the price of an external hard drive for a one time recovery and (b) I want to understand what is going on and it feels like there should be a simple fix to this problem.
EDIT: Based on Tetsujin's comment I realized something funny. I have OSX 10.11.6 so indeed it should not be able to read an APFS formatted disk. What I do not understand is how my disk2s3 became APFS. Is it because I installed Mojave on it? Is there a way to make it go back to whatever it was (I do not know what it was). Can I use gdisk to try HFS/HFS+ without destroying the data? The reason I think something else is wrong is because I was not able to boot from the disk either.
