Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I need to recover a 3TB USB HD. I started making a copy yesterday by running ddrescue in Terminal entering:

sudo ddrescue -v -f -n /dev/disk3 /Volumes/Seagate/disk_rescue.dmg disk_rescue.log

I've only just learnt how to use ddrescue so I was thrilled that it worked at all. It got to 1071 GB rescued (with no errors so far!) when I realized that a 2TB destination drive is going to fail when it runs out of space - oops.

I interrupted the copy with Ctrl-C and ran out and bought a 4TB hard drive to use as the destination drive instead. 4TB because I read that it needs to be bigger than the input drive to have enough space for the log file.

So my question: can I resume the copy of my failing hard drive on the new 4TB destination drive using the log file? Or do I have to start again from scratch? It's been running for about 16 hours so far, so if I don't have to start again that's a big time saver.

share|improve this question

Yes you can, just copy the image to the destination drive and adjust the output path accordingly.

share|improve this answer
Thanks! Once I've copied the image do I just type in the whole command that I typed before but with the adjusted output path? I can't actually see a .log file anywhere so I'm assuming that I don't have to go find it – Sadira Feb 20 '13 at 1:17
yes, that should work assuming you run the terminal in the same "working directory" as you had it before (i.e. you didn't/don't change directories after you launch(ed) the terminal) – nc4pk Feb 20 '13 at 2:40

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.