linux-kernel - Re: [Bug 37682] New: Kernel mis-detects size/position of partition created with Seagate DiscWizard (OnTrack Disk Manager)

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Date:	Sat, 18 Jun 2011 16:34:53 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	markk@...ra.co.uk, Andrew Morton <akpm@...ux-foundation.org>,
	bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Bug 37682] New: Kernel mis-detects size/position of partition created with Seagate DiscWizard (OnTrack Disk Manager)

On Saturday 18 June 2011 12:38:21 Paul Bolle wrote:
> Perhaps this means one is expected to use dmsetup(8) for this. I have
> never configured device-mapper at that level by hand. man 8 dmsetup is
> over 300 lines of (new for me) information. Without a disk like yours at
> hand, it's hard to say whether device-mapper allows to do stuff like
> this (ie, remapping an entire drive by 63 sectors) by hand.
> 
> Of course, for your particular drive it might be easier to just dd the
> actual partition (so skipping 63 sectors) into new file (a 20G image) on
> another drive. That image should be loop mountable. If that's correct
> you could then do with the drive as you please. Given its age, it may be
> wise to, say, shred(1) its corresponding device and drop the drive at
> your local recycling site.

You can also create a "correct" partition table to replace the old
one and directly point to the FAT partition:

# fdisk -c -u -C2435 -H255 -S 63 /dev/sdX

Command (m for help): p

Disk /dev/sdX: 0 MB, 0 bytes
255 heads, 63 sectors/track, 2434 cylinders, total 0 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: 0x00000000

  Device Boot      Start         End      Blocks   Id  System
/dev/sdX   *           9    16434494     8217243   54  OnTrackDM6

Command (m for help): d
Selected partition 1

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (1-39118274, default 1): ?
First sector (1-39118274, default 1): 126
Last sector, +sectors or +size{K,M,G} (126-39118274, default 39118274): +39102147

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): c
Changed system type of partition 1 to c (W95 FAT32 (LBA))

Command (m for help): a
Partition number (1-4): 1

Command (m for help): p

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: 0x00000000

  Device Boot      Start         End      Blocks   Id  System
/dev/sdX   *         126    39102273    19551074    c  W95 FAT32 (LBA)


Command (m for help): w
The partition table has been altered!


WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
information.
Syncing disks.
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