Re: [Bug-ddrescue] Re: I forgot to use a logfile

[Dave Burton]

address@hidden (Antonio Diaz Diaz) wrote:

> Hello Jason,
>
> Jason Reeve wrote:
> > Unfortunately I never started ddrescue with a log file, so if I do stop
> > it, am I right in thinking I may have to start the whole process again
> > if the DMG is unusable?
>
> You are right. Never start a rescue without a logfile. If everithing
> goes well it is easy to delete the logfile afterwards, but if there are
> errors the logfile can be very useful.


Indeed.  But it would not be difficult to write a small program
that reads an image file and creates a logfile which is better
than nothing.  It would simply assume that sectors containng
all zeros were unrecovered.

If you want to write such a program, Jason, you could use my
little sparsecopy.c program as a starting point, since it
already reads an image file and checks each sector to see
whether it is all zeros.  It is a small, quick-and-dirty
program, but it works; get it from
http://www.burtonsys.com/download/ddr2sr.zip

Hmmmm... in Linux, is there any way to tell the difference
between a block of zeros which is stored on the disk and a
block of zeros which is NOT stored (in a sparse file)?  If so,
it should be possible to create an excellent logfile from the
image file!  Does anyone know how to do this?

-Dave