[lug] disk image with dd

Gary Hodges Gary.Hodges at noaa.gov
Mon Jul 13 12:03:26 MDT 2009

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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