[ILUG] OT: damaged headers on External NTFS USB drive on dual boot Linux/Win 7 PC

[Andrew McGill]

On Mon, 19 Dec 2011 12:00:05 +0000
John Kinsella <John.Kinsella at staffmail.ul.ie> wrote:

> Hi - as above. Apologies for OT posing...
> 
> My pc is dual boot Linux/Win 7.
> 
> I have an external 512 GB USB drive, formatted as NTFS.
> 
> I was fuffing about in Win 7 moving my iTunes collection from an NTFS 
> (Win 7) partition on the PC internal drive to the USB drive.
> 
> At next (Win 7 & Linux) boots the USB drive was inaccessible..
> Maybe a Win 7 glitch, who knows..
> 
> (I have had no success Googling for Win 7 solutions.)
Google must be losing their touch :)

> Linux reports:
> root at jkcray:/home/kinsella# fdisk -lu /dev/sdc
> 
> Disk /dev/sdc: 500.1 GB, 500107862016 bytes
> 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x3bd15fd4
> 
>     Device Boot      Start         End      Blocks   Id  System
> /dev/sdc1              63   976768064   488384001    7
> HPFS/NTFS/exFAT
> 
> But when I use the Information option in gparted to examine the 
> /dev/sdc1 partition I get
> "ntfsresize seg fault.
> Unable to read the contents of this file system"..

Now this does not really mean anything to me, but it is possible that there is some kind of media fault on the disk - e.g. unreadable sectors, etc.  This would show up in the output of `dmesg' if it is the problem. If you do see that important parts of the disk are unreadable, there are two things you can do (and possibly both):

 * eliminate the USB part of the connection by plugging the disk directly into something like a SATA connector (if that is what it has internally).  I've seen intractable errors on USB disk 

 * copy the disk to a file with dd_rescue.  Once you have the file you can try to repair it.  The NTFS utilities might do better on a readable file than on a flaky disk.

There are also two sets of NTFS utilities - ntfs3g and the kernel ntfs utilities.  If the one doesn't work, try the other.

> Gparted graphically shows /dev/sdc as composed of two partitions,
> /dev/sdc1 (465.76 Gb) with the correct label
> and a small partition (2.49 Mb) unallocated.
> 
> Presumably the latter is the FAT or whatever the correct Windows term 
> for disk header?
Chances are that the partition table is correct as-is.  The tiny partition is probably filesystem creation rounding error, or for alignment.
> 
> Using dd I can see that there is still data on the disk..
> 
> root at jkcray:/home/kinsella# dd if=/dev/sdc skip=0 count=1000 bs=512 | 
> hexdump -C |grep -i Ctrl
> 00007fd0  20 43 74 72 6c 2b 41 6c  74 2b 44 65 6c 20 74 6f  | 
> Ctrl+Alt+Del to|
> 1000+0 records in
> 1000+0 records out
> 512000 bytes (512 kB) copied, 0.30871 s, 1.7 MB/s
> 
> 
> Is there any way to make the disk readable?
There's data and there's information ... 

&:-)