Will dd_rescue wipe my output hard drive?

Question

I'm planning to use dd_rescue (as per IT support's instructions) to try and get the data contents of a faulty hard drive.

We only have one external hard drive to back up onto which has enough free space to copy the recovered contents onto it. However, we have content on the external hard drive which we need to keep alongside the restored data from dd_rescue.

Will running dd_rescue wipe the external hard drive or will it keep the files on it intact and copy the recovered contents into a separate file or folder?

No dd_rescue documentation I can find suggests either.

Answer 1

Note that I'm talking about GNU ddrescue, which supersedes the original dd_rescue. See: What's the difference between ddrescue, gddrescue, and dd_rescue?.

It depends on what you choose as the target for ddrescue. From the ddrescue manual:

If you use a device or a partition as destination, any data stored there will be overwritten.

In that case you need to move the data off your drive first, or find another drive. You can, however, output to a file as well:

ddrescue /dev/hda0 /media/external/image.img

This .img will really be just raw data. It will be saved alongside your existing data on the external drive, but you should make sure there's enough space to write.