Re: Suggestion: A No-write Option, e.g. --scrub.

[Antonio Diaz Diaz]

Hi Ralph,

Ralph Corderoy wrote:
> I've just used dd(1) to repeatedly read an SD card until it got all the
> way through without an I/O error.  Quite a bit of the run time was
> reading what had already been successfully read because I was lazy, or
> had a better way to use my time.
>
> It occurred to me that ddrescue(1) would do a better job, but I wouldn't
> want a copy created in an output file.  I skimmed
> https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html but
> didn't see a way to do this, or a special meaning to an output file of
> /dev/null.

Thanks. I'll document this. As you suggest, /dev/null (combined with a 
mapfile) can be used to perform this task efficiently with a command like 
this one:

  ddrescue -f -r-1 /dev/sdcard /dev/null mapfile


> A --scrub would be quite handy to read repeatedly until the media's
> controller succeeds and re-maps the block internally.

The option '-r-1' (infinite retry passes) in the command above achieves 
exactly that.


Best regards,
Antonio.