I have an external disk that won't mount on my Mac:
/dev/disk6 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *2.0 TB disk6
1: EFI EFI 209.7 MB disk6s1
2: Apple_HFS 2.0 TB disk6s2
When I first got the disk (from a colleague) it would not mount. I saw that /dev/disk6s2
was set to Microsoft Basic Data
so I assumed that was the problem. I ran sudo asr adjust --target /dev/disk6s2 --settype "Apple_HFS"
to fix that and now (as seen above) disk6s2
is set to Apple_HFS
but it still won't mount.
The output of sudo gpt -r show /dev/disk6
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 2008
411648 3906617344 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
3907028992 143
3907029135 32 Sec GPT table
3907029167 1 Sec GPT header
I don't see any problems there but I'm getting into areas I'm not fully familiar with. I have no reason to think nor have I noticed any physical problems with the disk itself.
Any suggested steps or diagnoses?
MacPro (late 2013) OSX 10.11.6
Best Answer
The asr target option --settype "Apple_HFS" modifies the GPT partition type but not the file system. So the partition "content" is 48465300-0000-11AA-AA11-00306543ECAC (which is an indicator for a normal HFS+ partition) but the file system on disk6s2 still is NTFS/ExFAT/FAT32.
If the disk is empty, simply erase it with Disk Utility to whatever you need.
Changing the partition "content" with gpt or another similar tool doesn't alter the file system. Your volume may not mount if content and file system don't match!
BTW asr is not the proper tool to format volumes, create file systems or to change the partition type. This is rather done with newfs_XY, diskutil and gpt.
To determine or examine the file system you would have to open the volume as raw data and check for specific headers or fs structures.