[svlug] Failing external drive. Planning to DD the failing drive to new external drive. Help please

Roger E. Rustad, Jr. roger.rustad at gmail.com
Thu Nov 12 11:55:13 PST 2015

DDrescue is your friend.  It will make a log file, which could then make
sure you can resume if the hard drive stops and you have to reboot the

On Thu, Nov 12, 2015 at 10:57 AM, Sarah Newman <newmans at sonic.net> wrote:

> On 11/12/2015 07:44 AM, H P Ladds wrote:
> > I have an external hard drive failing and hope to DD the drive to a new
> external hard drive.
> >
> > Should I reformat the new drive to ext3 (or ext4) before DDing?
> >
> > The failing drive has two 500 gig partitions (I believe ext3). Should I
> DD the partitions separately or DD the entire drive?
> >
> > After DDing I'll try to retrieve the data. Oh and it is all data, no OS.
> What does "failing" mean? Is there data it can't read?
> If there's data it can't read, I would use ddrescue to copy the entire
> disk to an image. ddrescue has a way to keep track of data it can't read,
> so if
> you make two copies (one with the stuff it can't read set to 0 and one
> where the stuff it can't read is set to 1) you can do an md5sum on each
> (using
> both /dev/loop0 and /dev/loop1) and compare the md5sums to find corrupted
> files. I can't recall exactly how to do this off the top of my head, but I
> can try to dig it up if you aren't able to figure it out.
> The commands for setting up are losetup /dev/loop<0 or 1> <img> , kpartx
> -av /dev/loop<0 or 1> to add partition mappings. Then kpartx -dv /dev/loop<0
> or 1> & losetup -d /dev/loop<0 or 1> to tear it down again.
> --Sarah
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