I don't know if this has been covered before, but knoppix includes the program dd_rescue which is really a brilliant program for copying/imaging hard drives with bad sectors.

dd will give you lots of trouble when it encounters bad sectors, usually truncating the output or exiting when it gets a read error.

dd_rescue is much more forgiving.

"dd_rescue" without parameters will give you a list of command line parameters. Note that the command line syntax is much different from dd.

For example, "dd_rescue /dev/hda /dev/null" will copy from /dev/hda to /dev/null . I like to use this as a read test to see if an entire hard drive can be read.

I had a failing hard drive whose LBA sector 0 was completely unreadable. dd wouldn't even want to look at it. With dd_rescue I was able to get most of the good data off of this drive. Interestingly, knoppix 5.1 wouldn't even give me a /dev/hda in the device directory as it couldn't read the partition table in LBA 0 and kept retrying ad infinitum. I tried knoppix 3.9 and knoppix 6.0.1 and they would give me a /dev/hda even if LBA 0 was bad.