I am using an ubuntu live cd to help me recover some data off of a hard drive. I used lshw -C disk to find out which device I need to copy, /dev/sda in this case.I am using ddrescue -n to try and recover some data from a failing hard drive.  It stops at 100GB of a 500GB hard drive. After it finishes sudo lshw -C disk does not print anything.The next step in using ddrescue is to use sudo ddrescue -r 1 /dev/sda, but it reports there is no such file or directory.What is going on; why is lshw failing to report anything?Edit: Added sudo to relevant places.
lshw -C disk returns but prints nothing
ubuntu;data recovery;livecd;dd
It looks like the way in which your disk is failing is so bad that the kernel becomes unable to keep communicating with the disk.There are probably a lot of errors concerning the disk in /var/log/kern.log. If you post its contents here, people might have tips to help you recover more. (Post only the part from the first disk error, presumably triggered during the ddrescue -n, to the point where the kernel deactivates sda; if there's a long and repetitive bit in the middle, it's ok to cut the repetitions.) But don't expect miracles, there's a chance that the last 400GB are simply beyond recovery without spending thousands of dollars on a professional service.