A friend gave me his "broken" external-usb-hard drive which contains important stuff. So I plugged in the usb into my (linux-)notebook and ran
The output shows, that the OS wasn't able to detect any partition or even mount the disc. It was full of error-messages all beginning with
blk_update_request: I/0 error, dev sda ....
My first try was to run
ddrescue -n -N -d /dev/sda test.img test.logfile. Unfortunately the produced test.img-file was empty after ddrescue stopped running a few hours later. Using ddrescue and also
smartctl -t short /dev/sda to let the harddrive doing a self check (which ends in a "everything seems fine"-like message) covers all my knoweledge of datarescue steps. So are there any other possible steps to understand the situation and do a file-rescue/disc-repair?