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It's very tempting for me to go on a rant here about GParted and Linux, but I'll do my best to avoid it. :)

Question:

Why does GParted claim that my disk is corrupted and GPT, whereas the Disk Utility thinks everything is fine?

My only partition on the disk (NTFS) has Windows 7 x64 on it, and has absolutely no problems -- I never had any problems with it, and I ran CheckDisk to make sure.

Why is GParted behaving this way?

(I was going to post this on AskUbuntu, but since GParted isn't really limited to Ubuntu, I posted it here. I'm using Ubuntu 11.04 x64's boot disc.)

Screenshot

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Try running TestDisk. –  Hello71 Jun 6 '11 at 0:44
    
@Hello71: And do what? –  Mehrdad Jun 6 '11 at 0:46
    
@Mehrdad: Rewrite the partition table? –  Hello71 Jun 6 '11 at 0:47
    
@Hello71: O___O What makes you think the problem is with the partition table and not GParted? Like I said, the Ubuntu disk utility says it's fine, and Windows boots just fine and Disk Management also works fine. –  Mehrdad Jun 6 '11 at 0:47
    
@Hello71: Thanks for the advice... I rewrote the partition table, and now I get INT18: BOOT FAILURE on boot. Was that what was supposed to happen? x__x –  Mehrdad Jun 6 '11 at 1:37
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2 Answers

up vote 4 down vote accepted

Chances are the disk used to be a GUID Partition Table (GPT) disk. Such disks have partitioning data from sectors 0-33 (typically) and also in the last 33 sectors of the disk. If a GPT disk is repartitioned by a GPT-unaware utility, that utility is likely to replace just sector 0 (the MBR), leaving most of the GPT data intact. Technically, the disk is then an MBR disk; however, some partitioning tools, including many Linux tools that are based on libparted (including GParted) become confused by this. They may show the disk as being completely blank or show the old GPT partitions rather than the new MBR partitions. This is a bug in libparted, but it's triggered by some inconsistent data on the disk.

The solution is to wipe the old GPT data. This can be done various ways, but the simplest is probably to use FixParts, which is designed for this and some other partition table repair tasks. Alternatively, you could use dd to wipe sector 1 (numbered from 0) and the final sector on the disk; that's where the GPT signatures that are confusing libparted reside.

Sorry I didn't get here sooner, Mehrdad. My guess is that when you rewrote the partition table you also wiped out the boot loader in the MBR. Re-installing your boot loader should fix that problem. It's possible that you wrote the wrong partition table, though, which would be harder to fix.

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Lol, sorry? For what?! That's excellent information you have there, I appreciate the answer! :) I'll take a look at it when I get the chance. (It was just a virtual machine, don't worry... my data isn't at risk. :P) –  Mehrdad Jun 21 '11 at 4:19
    
From your later comments it sounded as if you'd already replaced the partition table, possibly rendering my information moot. If you're still having the problem, though, then it's still relevant.... –  Rod Smith Jun 22 '11 at 4:18
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There is a nice post here, " Today, 99% of PC uses a table partition standard named "DOS partition table". As you can guess, it's quite old, and was designed when OS used 10Mbytes hard drive. So a new standard was defined by Intel long time ago (but not as old as DOS!) which is better. This partition table is read bu BIOS at boot, so for backward compatibility, the GPT start with a fake DOS partition table to make old BIOS understanding it's not a real DOS partition table. The installer can't continue because it understand nothing on what is your disk, and can make serious damage to existing data. This GPT standard is used on Apple computers and from few times on some professional PCs. Is this disk coming from a Mac or was it formated for a Mac ? You can boot on Ubuntu CD, choose "Try", then System->Administration->Gparted Partition Editor, then erase current partition table (which will erase all data) and recreate a new DOS partition table. After installer should work. " which is really straightforward to solve.

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please do not use links as answers. it is encouraged to post all the relevant information here and use links as reference. if the link gets broken, so does your whole answer. –  Lorenzo Von Matterhorn Mar 13 '13 at 22:11
    
@Znau, can you upvote me now as I have given the answer. –  mmrs151 Mar 14 '13 at 8:02
    
i didn't downvote you in the first place. also, upvotes are not to be asked for. –  Lorenzo Von Matterhorn Mar 14 '13 at 14:16
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