CAUTION:
I would like to point that relates to an unfinished image.
In any event, anything less than a 100% recovery will leave portions on
the target image/drive that have not been written to by ddrescue.
If copying to a brand new hard drive, those areas are (hopefully) likely
to be zeros. But in any other case, those areas will contain whatever data
was there previously. For someone that uses their system for data recovery
on a regular basis, and is using image files or reusing hard drives, those
areas could contain data from a previous recovery! This could be a privacy
issue in some cases, but also could cause an issue with running any other
sort of repair/file recovery tools on the recovered image/drive.
The unrecovered parts could contain "garbage" data that could affect
accurate recovery. In these cases I would recommend using the fill mode
of ddrescue to fill any unfinished/untried areas with zeros.
Example command:
ddrescue --fill-mode=?/*- /dev/zero recovered_image logfile
This would write zeros to any portion of the recovery that was not
successfully read from the source.
Reference:
https://lists.gnu.org/archive/html/bug-ddrescue/2013-11/msg00011.html
