Knoppix To the ddrescue
A Good Disk Gone Bad
I have an external USB drive that seemed to get a bit overheated, and dropped a couple of sectors. That was bad, since I couldn’t access it from Windows XP, and chkdisk didn’t help.
chkdisk could find the bad sectors but couldn’t repair them.
So I turned to Linux to help fix the problem.
What I Needed
First I needed to pick up another USB external drive. Did that from newegg.com (they had the best prices at the time, and free shipping).
Then I created a Knoppix live CD. I had recently read an article on this, and a couple of the guys from the office recommended it too. I suppose I could have hooked the drives to my Red Hat Linux box, but I wanted to try something new anyway.
I went to the Knoppix download page and pulled down the ISO, which I burned to CD.
From doing research on the web, I found an open source utility called TestDisk. The readme for TestDisk was most helpful, and mentioned that TestDisk, dd_rescue also came on the Knoppix Live CD. It also mentioned a faster and perhaps better implementation of a disk rescue called ddrescue, from Antonio Diaz.
I downloaded ddrescue, built it on my Linux box, and stowed it on my C: drive on my Windows box, just in case.
Getting Started
My original effort was to boot Knoppix and use the dd_rescue program that came with the Live CD. It was slow. Over a 20 hour period it had only done about half of the disk.
I needed my Windows box back for certain things, so I aborted the process.
When I came back to it several days later, I tried the ddrescue instead.
ddrescue works in two passes. On the first pass, it grabs all the good sectors.
./ddrescue -n /dev/old_disk /dev/new_disk rescued.log
The second pass grabs the error stuff, reading the info from the rescued.log
./ddrescue -r 1 /dev/old_disk /dev/new_disk rescued.log
This went much faster, and since I had to be out all day, I just let it run. The next morning, it had completed, and I ran the second pass — took maybe 15 minutes.
I’m Back, Baby!
And so, after all of that, I have my stuff back on my new drive. I’ll format the old one and use it for temporary things, things that i can afford to lose if it goes flakey again…..
Knoppix — check it out.
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