Re: [Bug-ddrescue] possible bug on GNU ddrescue

[Antonio Diaz Diaz]

Prashant Subbarao wrote:
> I wanted to determine which files were in either a "failed block
> non-scraped" or "failed block bad-sector(s)". So what I did is I went
> through the log file and, using sed, converted all the / to a -.

There is no need to change the '/' to '-'. Just use "--fill-mode=/-". Or 
better yet, finish the rescue by removing the -n option, then fill the 
bad sectors.


> i executed this command:
>
> ddrescue --force --fill-mode=l- tmpfile /dev/sdc rescue.JustPlusMinus.log
>
> I was under the impression that ddrescue would *read* the mapfile
> rescue.JustPlusMinus.log and write the string in tmpfile to every sector
> marked - in the mapfile rescue.JustPlusMinus.log. *Did I do this correctly?*

Yes.


> (Again, emphasis my own.) I am concerned because the mapfile
> rescue.JustPlusMinus.log seems to have been overwritten and now looks like
> this:

Ddrescue always compacts the mapfile by joining adjacent blocks with the 
same status. As you changed '/' to '-', you fooled ddrescue into 
thinking that non-scraped sectors were bad sectors instead.


> *Is *ddrescue* reading the mapfile *rescue.JustPlusMinus.log* and
> overwriting it? Or has it stored all the bad sectors elsewhere (perhaps in
> the MBR) and it's only writing to the mapfile **rescue.JustPlusMinus.log?*

http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Fill-mode

In fill mode mapfile is updated to allow resumability when interrupted 
or in case of a crash, but as nothing is being rescued mapfile is not 
destroyed. The status line is the only part of mapfile that is modified. 
(Compaction is not considered modification).


Best regards,
Antonio.