[lug] disk image with dd

Ben bluey at iguanaworks.net
Mon Jul 13 12:36:34 MDT 2009

I believe the syntax is slightly different than dd. -- man dd_rhelp for 
more info, but I believe what you want is

dd_rhelp /dev/hdc /dev/hdd


Gary Hodges wrote:
> I must be doing something wrong...
>  >./dd_rhelp if=/dev/hdc of=/dev/hdd
> Results in:
> dd_rhelp: error: Please specify a usable file as first argument.
> The following drives are seen during boot:
> hda: IBM-DHEA-36480, ATA DISK drive
> hdb: ST340014A, ATA DISK drive
> hdc: ST3250824A, ATA DISK drive
> hdd: WDC WD2500PB-55FBA0, ATA DISK drive
> hdc is the disk I want to copy from.  hdd is the disk that I want to 
> copy to.
>  >fdisk /dev/hdc
> Command (m for help): p
> Disk /dev/hdc: 250.0 GB, 250059350016 bytes
> 255 heads, 63 sectors/track, 30401 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>     Device Boot      Start         End      Blocks   Id  System
> /dev/hdc1   *           1        5099    40957686    7  HPFS/NTFS
> /dev/hdc2            5100       30401   203238315    7  HPFS/NTFS
> Ben wrote:
>> If you have any errors on the hard drive, dd will just stop. I'm a big 
>> fan on dd_rhelp (I think it is just a wrapper to ddrescue which is a 
>> wrapper to dd) as it jumps over bad regions (fills them with 0's) and 
>> comes back and figures out of the size of the bad region smartly. You 
>> can start/stop it many times and it picks up where it was left off. 
>> Basically it spends its time getting the 'easy' data and then 
>> progressively works harder on the data near bad regions. But otherwise, 
>> you are right about the mount command and making a disk image.
>> Gary Hodges wrote:
>>> Hi.  I have a drive from a Windows machine (NTFS) that I think may have 
>>> some problems.  I'd like to make a copy to play with so I can leave the 
>>> original undisturbed for now.  Is this what I should do?
>>>    dd if=/dev/hdx of=/dev/hdy   # where x=original, y=copy
>>> Along those lines, if I did the following
>>>    dd if=/dev/hdx of=/path/to/image
>>> would I be able to mount the image with something like?
>>>    mount -o loop /path/to/image /mnt/mountpoint
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