[plug] Partitions on external hard disk gone awry

Lucas van Staden lvs at dedmeet.com
Fri Oct 3 21:14:25 WST 2008


I recently had to restore an external usb drive that got corrupted.
Not exactly the same issue (only had one big ntfs partition), but was
also related to being missing.

I was also scared to fiddle with the drive, and further destroy the data.

Some googling revealed this page, from which I used parts to recover my


The part that was most useful:

# dd if=/dev/sda of=/tmp/r1 bs=512

which makes an image of your drive, and then you can work on the image
only, with the drive disconnected.

All in all this page was very informative, and tought me a thing or

Hope any of this helps your situation.


Haydon Knight wrote:
> Hi,
> I have messed up the partitions on an external hard drive and would
> like to restore it without deleting my data, but don't know how to do
> this.  I would appreciate any help from pluggers greatly...
> I run computers with XP, vista, mac osx 10.5, and ubuntu linux hardy
> 8.04.  I own a 500GB external USB hard drive and wanted to store data
> on it formatted so that all the above operating systems could read and
> write to it.  The external HDD had 3 partitions on it:
> + a mac time machine partition (hfs+)
> + a linux partition (ext3) that I use for backups plus storing some other stuff
> + another junk ext3 partition
> Windows wasn't seeing any of the partitions so I decided to reformat
> the 3rd partition to a couple of NTFS partitions using gparted.  I set
> this up from ubuntu but forgot to close the nautilus windows that pop
> up showing the contents of the partitions.  gparted reported an error
> something like cannot repartition as in use and suggested I wouldn't
> be able to see the partitions until a reboot.  I rebooted but now the
> disk seems to be in a funny state:
> + the first 2 partitions work fine in general use
> + the 3rd partition has disappeared
> + gparted terminal reports 'Invalid partition table on /dev/sdc --
> wrong signature 0.'
> + gparted gui shows the whole disk as unallocated
> I would like to just restore the disk but can't seem to use gparted to
> do it.  I'm not keen on copying the hfs+ partition to another disk as
> I don't know of a utility I can trust - as I understand it a time
> machine file system has an extra property of directories being able to
> have multiple hard links and I'm not sure whether backup programs
> handle this properly or not.  Also I'm not sure how fussy osx is about
> moving around of time machine volumes.
> I'm very worried about taking a step that irreversibly affects my data.
> So can anyone recommend a tool/method that can restore the partition
> table?  Or if that is not possible, a tool that can definitely backup
> my hfs+ and ext3 partitions safely and reversibly?
> Thanks a lot!
> -Haydon
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