I just got done answering this question for someone at work:
What was that app that allowed you to duplicate the failing hard drive?
So I figured, why not put it out there for the Internets to see?
It’s the dd_rescue command within Knoppix. (I’ve always used 5.0 or 6.1 – I think dd_rescue is still included in version 7)
You need to boot to the Knoppix CD/DVD and run dd_rescue on the DISK, not the PARTITION.
Syntax:
dd_rescue /dev/sda /dev/sdb
Given that /dev/sda is your source drive, and /dev/sdb is the destination drive.
You can check your disk configuration like this:
fdisk -l
Read the output from there to see which disk is which. Your best bet is to use a sanitized drive as the destination so it’s easier to tell which disk has stuff on it and which doesn’t.
Since this is all command line, I HIGHLY recommend running a practice job using data that doesn’t matter before going forward with real data. This process can easily ruin good data if you have the command backwards.
Additional switches:
You can use these switches to “sandwich” a bad spot on the drive and pick up as much data as possible.
-s defines the start position.
Ex: (will start at 15G and go forwards)
dd_rescue –s 15G /dev/sda /dev/sdb
-r defines working from front to back
Ex: (will start at 15G and go in reverse, back to the beginning of the drive)
(-r does not use DMA buffer, which can increase error correcting abilities)
dd_rescue –r –s 15G /dev/sda /dev/sdb
