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I lost my GUID Paritition label to Fdisk


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#1
rimmi2002

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I had a perfect working retail install of Snow Leopard and Win7. I have reinstalled Win 7 multiple times and had to do it one more time. I did it and used by USB stick to boot into OSX to restore chameleon as boot loader. In the past it has never been a problem. Now however the chameleon instructions were not working. I noticed that my MAC DISK is no longer GUID Parition. It is now Fdisk? How did it loose it's GUID TABLE?

Below is a screen shot from diskutility with my attempt at using fdisk440 and it failing. OSX disk is Disk 1.Please advise if there is any way to reverse this. THanks.

About the only thing I did different this time compared to last time was that I installed Acronisc true image back up home plus on win7 and made a copy of the my win7 parition. I am not sure if that messed things up or something else, but I am not sure how a GUID parition changed to a Fdisk. Makes no sense to me.

Any help will be appreciated. tHanks.

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#2
srs5694

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I'm not 100% sure what happened, but my suspicion is that the Acronis software, or possibly something else, overwrote the main GUID Partition Table (GPT) data. If you're lucky, the backup data are intact, in which case the disk can be fully recovered. It's likely that there are several partition editors that will do the job, but I don't know the details for most. I do know that my own GPT fdisk will work. You can either download the Windows version from the Sourceforge download page or use a Linux emergency disk with GPT fdisk, such as PartedMagic or System Rescue CD. When you launch the program on the disk, I expect you'll see something like this:

# gdisk /dev/sdc
GPT fdisk (gdisk) version 0.6.10

Caution: invalid main GPT header, but valid backup; regenerating main header
from backup!

Caution! After loading partitions, the CRC doesn't check out!
Warning! Main partition table CRC mismatch! Loaded backup partition table
instead of main partition table!

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: damaged

Found valid MBR and corrupt GPT. Which do you want to use? (Using the
GPT MAY permit recovery of GPT data.)
 1 - MBR
 2 - GPT
 3 - Create blank GPT

Your answer: 2

Command (? for help): p
Disk /dev/sdc: 31576064 sectors, 15.1 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 6C03B3D9-5D76-4968-914D-607C083F2082
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 31576030
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)	End (sector)  Size	   Code  Name
   1			2048		16779263   8.0 GiB	 8200  Linux swap
   2		16779264		31576030   7.1 GiB	 AF00  Apple HFS/HFS+

This is an example where I re-created the problem on a test disk (/dev/sdc here; yours would probably be /dev/sdb in Linux or 1: in Windows, but it could be something else). Note the partition table scan, which shows "MBR: hybrid" and "GPT: damaged." I opted to use GPT, which recovered the partitions, as shown by "p" (just two of them in my example). Typing "w" at a menu will then save the recovered partition table and exit from the program. (Your hybrid MBR will be left intact; or you can generate a fresh one by using the "h" option on the recovery & transformation menu, if you think the current hybrid MBR is incorrect.) If my hypothesis of the cause is correct, saving the recovered GPT data will wipe out the Acronis data on the drive. Acronis may try to re-create the data, therefore trashing the disk again. Thus, if I'm right you'll have to ditch that software.

It could be that something else has caused the problem, of course. If that's the case, then GPT fdisk might or might not help. If all of the GPT partitions are mirrored in the hybrid MBR, though, GPT fdisk will at least create a suitable GPT disk out of the remnants in the hybrid MBR.

Incidentally, hybrid MBRs are flaky and dangerous, as you've discovered. If at all possible, I recommend avoiding them. With the number of disks you've got, you can probably isolate the Windows and OS X boot partitions to different disks, using pure MBR on the Windows boot disks and pure GPT on the OS X boot disk. This should be more reliable in the long run, although it may require some juggling of your installations in the short run. Note that both OSes can read both partition table types, so shared data partitions can be on either drive type. (This is assuming you're using Windows Vista or later; the situation is dicier with Windows XP and earlier.)

#3
rimmi2002

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srs5694....Thanks so Much!!!!

I did exactly as you wrote and things are back to normal. It went almost exactly as you detailed it in your post. I chose option "p" and then option "w" and things are back to normal. I have GUID partition with the s01 being the EFI partition. Attached the screenshot below. And acronis has been long deleted on my computer. Once again thanks for your help. Really appreciate it. Perfect solution.

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#4
srs5694

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Glad to hear it worked for you! Incidentally, GPT fdisk also has a backup option. It's the "b" option on the main menu. Using it will create a backup file of the GPT data, which simplifies recovery in case of really serious damage. Of course, as you've discovered, GPT has its own backup, but having a backup file on a flash drive or whatnot is extra insurance in case you accidentally delete partitions using a partition editor or something.

#5
dwhits90

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I'm having a related issue and someone told me I should post here. PLEASE! Any help would be better than nothing!

So I have a huge issue going on right now. Basically I cannot get my hard drive working, which is a huge problem seeing as I cannot apply to graduate school for architecture without the documents on there. I would GREATLY appreciate any help. (Note - I'm not hugely knowledgeable about a lot of the backend tech stuff on computers but am a very fast learner and have a VERY solid grip on how to use macs).

Here's the story:

I have a 1TB WD external hard drive. I gave it a FAT32 partition so I could transfer documents between my MAC and my PC in my architecture studio. The hard drive was working fine for a while and then last week, I noticed that it gave me an error message saying that I could read documents on the hard drive but I would not be able to copy new documents to the hard drive. Then, the next time I plugged the hard drive into my computer, I got an error message telling me that "The disk you inserted was not readable by this computer." And I haven't been able to get it to work since. I opened disk utility and the partition's name has changed to disk2s1 from it's original name. Also, disk utility is unable to repair the disk.

I downloaded and paid for Stellar Phoenix. It ran for a week and was able to recover some of the files (so I KNOW the files are still there) but I know it didn't even BEGIN to scan the depths of my hard drive because it appeared to freeze at about 5% of the way through the scan (at least I think it was frozen because it was monitoring the same sector for 2 days) and I stopped the scan and recovered some of the files it had detected. These files were recovered to the 2 TB G-Technology hard drive that I have since purchased at the apple store. I then purchased DiskWarrior. DiskWarrior gave me an error message that read:
Directory cannot be rebuilt, the file system is unsupported.
This disk is not a Macintosh disk.
This disk does not appear on the desktop.
This disk is 1 TB in size.
Disk ID: disk2s1
Sectors: 1,953,458,174 (512 Bytes each)
Drive Format: FDisk Partition Scheme
File System: MS-DOS/PC
Model: WD

I cannot for the life of me figure out what this FDisk Partition Scheme means/is referring to I used a mac to partition the drive and to prove it, the hard drive was working on the Mac. It's almost as if suddenly, something changed the drive format.

After doing extensive searches online, it appears my problem is SIMILAR to this post ->http://forum.voodoop...hp?topic=1593.0
The poster was able to solve the issue, but I don't have the technical understanding to figure out what he did. I attached an image of what the terminal says when I list the drives.

If there is ANYONE out there that is willing to help me out, I would truly be endlessly appreciative. You have no idea how much it would help me out. This is really an incredibly serious problem for me, and I'm really just ready for this issue to be done with, but I don't want to spend any more money on it, especially if it's something that can be fixed without spending money and I just don't know how to do it.

Screen shot 2013-03-11 at 7.58.32 PM.png

#6
theconnactic

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Did you give the software linked by srs5694 a go?

I suggest you P.M. him with the link of this topic: hopefully he'll answer and give you further help on the subject.

Anyway, before doing anything to your disk, since there's data there that's not anywhere else, wait for other opinions or for srs5694 to answer.

Good luck!

#7
dwhits90

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Thanks so much for the suggestion! I'll get on that right away





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