Settings to manually add Fat32 partition

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joneseybones
Posts: 2
Joined: 13 Oct 2017, 03:39

Settings to manually add Fat32 partition

#1 Post by joneseybones » 13 Oct 2017, 04:13

Hello, thanks for all your help with this great piece of software! Will gladly send beer money your way.

I'm having a bad day, and somehow managed to format the wrong Fat32 drive to HFS+, but killed the diskutil process immediately after the partition map was created, so I've been hoping I can just recreate the FAT32 boot to recover the entire partition. I did read in another post that this is difficult with HFS+, so I'm expecting this will not be possible. I have run file recovery programs and can see my files, and so I'm sure Photorec can recover them, but of course would like to maintain filenames and structure.

I'm currently running a very long process of running through the "Recovery of a Formatted Partition" guide (the RebuildBS process looks like it will take a number of days), though I'm seeing some other strange errors as well. When I run my Quick Search analyze, I get a "current number of heads per cylinder mismatch. Should be "1" but is currently "8". I see a Warning message stating that there is a :bad starting sector (CHS and LBA don't match)".

I will of course continue to run the RebuildBS process as needed, but am curious if I should be trying to resolve this another way, due to my confusion over the errors that I see from the Analyze quick search. Should I at this point modify the geometry? Manually create the FAT32 boot partition?


Output of running the analyzer quick search below:


Code: Select all

Thu Oct 12 20:06:34 2017
Command line: TestDisk

TestDisk 7.1-WIP, Data Recovery Utility, July 2017
Christophe GRENIER <grenier@cgsecurity.org>
http://www.cgsecurity.org
OS: Darwin, kernel 15.6.0 (Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.6
Compiler: GCC 4.0
Compilation date: 2017-09-24T12:32:35
ext2fs lib: 1.42.8, ntfs lib: libntfs-3g, reiserfs lib: 0.3.1-rc8, ewf lib: 20120504, curses lib: ncurses 5.4
Hard disk list
Disk /dev/disk0 - 751 GB / 699 GiB - 1467339812 sectors (RO), sector size=512
Disk /dev/disk2 - 4000 GB / 3726 GiB - 7814037167 sectors, sector size=512
Disk /dev/rdisk0 - 751 GB / 699 GiB - 1467339812 sectors (RO), sector size=512
Disk /dev/rdisk1 - 750 GB / 698 GiB - 1464935424 sectors (RO), sector size=512
Disk /dev/rdisk2 - 4000 GB / 3726 GiB - 7814037167 sectors, sector size=512

Partition table type (auto): EFI GPT
Disk /dev/disk2 - 4000 GB / 3726 GiB
Partition table type: Intel

Analyse Disk /dev/disk2 - 4000 GB / 3726 GiB - 7814037167 sectors
Geometry from i386 MBR: head=255 sector=63
BAD_RS LBA=1 1339
check_part_i386 1 type EE: no test
get_geometry_from_list_part_aux head=1 nbr=2
get_geometry_from_list_part_aux head=8 nbr=1
get_geometry_from_list_part_aux head=16 nbr=1
get_geometry_from_list_part_aux head=32 nbr=1
get_geometry_from_list_part_aux head=64 nbr=1
get_geometry_from_list_part_aux head=128 nbr=1
get_geometry_from_list_part_aux head=240 nbr=1
get_geometry_from_list_part_aux head=255 nbr=2
Current partition structure:
 1 P EFI GPT                        1 4294967294 4294967294

Warning: Bad starting sector (CHS and LBA don't match)
No partition is bootable

search_part()
Disk /dev/disk2 - 4000 GB / 3726 GiB - 7814037167 sectors
FAT32 at 40/0/1
check_FAT: Unusual media descriptor (0xf0!=0xf8)
FAT1 : 32-3182
FAT2 : 3183-6333
start_rootdir : 6334 root cluster : 2
Data : 6334-409599
sectors : 409600
cluster_size : 1
no_of_cluster : 403266 (2 - 403267)
fat_length 3151 calculated 3151
heads/cylinder 16 (FAT) != 1 (HD)
sect/track 32 (FAT) != 1 (HD)

FAT32 at 40/0/1
     FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB

HFS+ magic value at 409640/0/1

HFS+ magic value at 409640/0/1
part_size 3518398048
     HFS                       409640 7813774983 7813365344
     HFS+ blocksize=8192 + Backup, 4000 GB / 3725 GiB
get_geometry_from_list_part_aux head=1 nbr=4
get_geometry_from_list_part_aux head=8 nbr=4
Warning: the current number of heads per cylinder is 1 but the correct value may be 8.

Results
   * FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB
   P HFS                       409640 7813774983 7813365344
     HFS+ blocksize=8192 + Backup, 4000 GB / 3725 GiB
Change partition type:
   P FAT32                     409640 7813774983 7813365344
     HFS+ blocksize=8192 + Backup, 4000 GB / 3725 GiB

interface_write()
 1 * FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
 2 P FAT32                     409640 7813774983 7813365344
simulate write!

write_mbr_i386: starting...
write_all_log_i386: starting...
No extended partition
Partition table type (auto): EFI GPT
Disk /dev/disk2 - 4000 GB / 3726 GiB
Partition table type: Intel

Analyse Disk /dev/disk2 - 4000 GB / 3726 GiB - 7814037167 sectors
Geometry from i386 MBR: head=255 sector=63
BAD_RS LBA=1 1339
check_part_i386 1 type EE: no test
get_geometry_from_list_part_aux head=1 nbr=2
get_geometry_from_list_part_aux head=8 nbr=1
get_geometry_from_list_part_aux head=16 nbr=1
get_geometry_from_list_part_aux head=32 nbr=1
get_geometry_from_list_part_aux head=64 nbr=1
get_geometry_from_list_part_aux head=128 nbr=1
get_geometry_from_list_part_aux head=240 nbr=1
get_geometry_from_list_part_aux head=255 nbr=2
Current partition structure:
 1 P EFI GPT                        1 4294967294 4294967294

Warning: Bad starting sector (CHS and LBA don't match)
No partition is bootable

search_part()
Disk /dev/disk2 - 4000 GB / 3726 GiB - 7814037167 sectors
FAT32 at 40/0/1
check_FAT: Unusual media descriptor (0xf0!=0xf8)
FAT1 : 32-3182
FAT2 : 3183-6333
start_rootdir : 6334 root cluster : 2
Data : 6334-409599
sectors : 409600
cluster_size : 1
no_of_cluster : 403266 (2 - 403267)
fat_length 3151 calculated 3151
heads/cylinder 16 (FAT) != 1 (HD)
sect/track 32 (FAT) != 1 (HD)

FAT32 at 40/0/1
     FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB

HFS+ magic value at 409640/0/1

HFS+ magic value at 409640/0/1
part_size 3518398048
     HFS                       409640 7813774983 7813365344
     HFS+ blocksize=8192 + Backup, 4000 GB / 3725 GiB
get_geometry_from_list_part_aux head=1 nbr=4
get_geometry_from_list_part_aux head=8 nbr=4
Warning: the current number of heads per cylinder is 1 but the correct value may be 8.

Results
   * FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB
   P HFS                       409640 7813774983 7813365344
     HFS+ blocksize=8192 + Backup, 4000 GB / 3725 GiB

interface_write()
 1 * FAT32 LBA                     40     409639     409600 [EFI System Partition] [EFI]
 2 P HFS                       409640 7813774983 7813365344
simulate write!

write_mbr_i386: starting...
write_all_log_i386: starting...
No extended partition

TestDisk exited normally.
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cgrenier
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Re: Settings to manually add Fat32 partition

#2 Post by cgrenier » 14 Oct 2017, 09:24

You have a 4TB harddisk using 512 bytes sectors, a FAT32 is limited to 2TB.
diskutil has been able to write a hfs superblock and its backup superblock, so even if you had an exFAT (a good possibility for disk over 2 TB), testdisk will not find it anymore.
You can always use PhotoRec to recover your data but it will take a very long time to analyze a 4TB disk and you need enough space on another disk to store the recovered files.
So you may want to try other data recovery utilities including commercial ones to see if they can find your data with the filenames.

joneseybones
Posts: 2
Joined: 13 Oct 2017, 03:39

Re: Settings to manually add Fat32 partition

#3 Post by joneseybones » 19 Oct 2017, 07:55

Yes, it had been incorrectly formatted to be a Fat32 and had previously limited the size of the disk to 2TB (another dumb mistake). When I run a RebuildBS in testdisk, it does find a number of directories with full filenames, but not the / directory. I assume based on your reply that there is essentially nothing to be tried at this point to manually recover the partition?

Do you have a recommended commercial product?

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