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

Michael Eager eager at eagercon.com
Thu Nov 12 08:26:26 PST 2015

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.

You should not use dd to copy data from one disk partition to another.
Use rsync, cpio, tar, or cp.

> Should I reformat the new drive to ext3 (or ext4) before DDing?

Assuming that the new drive is identical to the old drive,
however you format the partition on new drive, when you copy the old
partition to the new one using dd, the format will be replaced
by the format of the partition on the old drive.  In fact, there is
no need to format the drive when you use dd to copy a partition.
(But, as I said, don't use dd.)

> The failing drive has two 500 gig partitions (I believe ext3). Should I DD the partitions separately
> or DD the entire drive?

Using dd to copy from one disk to a disk with a different size or
organization is unlikely to work.  At best, you will lose space.
At worst, the drive will be unmountable.

> After DDing I'll try to retrieve the data. Oh and it is all data, no OS.

If you want to use dd, you can create an image of the failing drive on
a spare drive, mount the image using the loopback device, and copy from the
image to your final destination using rsync.  This is sometimes useful if
the old drive is failing, so you have to make multiple copies using dd.

Michael Eager	 eager at eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077

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