Copying USB stick fails with device errors

[JD]

On 06/06/2012 05:41 PM, Alex wrote:
> Hi,
>
> I'm trying to copy a USB stick that I purchased that's supposed to
> contain a bootable desktop with a bunch of applications like firefox,
> openoffice, etc. The USB stick somehow actually contains two devices.
> One has a vfat filesystem and the other appears to be NTFS. When
> mounted, it has some sort of fedora variant in a tarball on it that's
> actually the bootable desktop.
>
> When I try to use dd to copy it, it eventually times out, produces an
> error like "sdb: unable to read partition table" and makes the device
> entirely inaccessible. I'm also unable to mount the resulting dd image
> as a loopback vfat filesystem once my copy has completed.
>
> There seems to be a disparity between what fdisk shows is the length
> of the filesystem and how much space is actually allocated? How did
> they create two devices within the one device?
>
> dmesg contains this info when I insert the USB stick:
>
> [1857968.944942] sd 75:0:0:0: [sdb] 7559249 512-byte logical blocks:
> (3.87 GB/3.60 GiB)
> [1857968.945310] sd 75:0:0:1: [sdc] 25307055 512-byte logical blocks:
> (12.9 GB/12.0 GiB)
>
> Here's the output from fdisk:
>
> # fdisk -l /dev/sdb /dev/sdc
>
> Disk /dev/sdb: 3870 MB, 3870335488 bytes
> 45 heads, 4 sectors/track, 41995 cylinders, total 7559249 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: 0x261e6d11
>
>     Device Boot      Start         End      Blocks   Id  System
> /dev/sdb1   *           4     5242859     2621428    b  W95 FAT32
>
> Disk /dev/sdc: 13.0 GB, 12957212160 bytes
> 229 heads, 55 sectors/track, 2009 cylinders, total 25307055 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: 0x7d2c8154
>
>     Device Boot      Start         End      Blocks   Id  System
> /dev/sdc1            9048    24272568    12131760+   7  HPFS/NTFS/exFAT
>
> # file usbstick.dd
> usbstick.dd: x86 boot sector; partition 1: ID=0xb, active, starthead
> 1, startsector 4, 5242856 sectors, code offset 0x31
>
> What's the proper way to copy the entire USB stick as an image?
>
> I suspect the issue is that the bootsector is within the first four
> blocks, and the filesystem begins after that. How can I tell "mount"
> to look for the filesystem after the first four blocks?
>
> Somehow when I insert the USB stick on my fedora16 desktop, it's
> already mounted (by udev?) and I can see the contents, so there is a
> valid filesystem on the original USB stick.
>
> Thanks,
> Alex
When fedora automounts your usb thumb drive,
which device does it mount?
sdb1 or sdc1?
Also,   the file usbstick.dd:
is this the file you created by attempting to dd
which of the 2 devices? sdb  or  sdc?