[Linux] "Fixing" failed download

[StephenW]

--- Larry Kagan <me@larrykagan.com> wrote:

> Sorry, my last response doesn't apply.  It's still too early for me.
> 
> Kwan Lowe wrote:
> >> Kwan Lowe wrote:
> >>     
> >>> Anyone know of a way to "fix" a failed DVD ISO download?  I have an ISO
> image of
> >>> Centos 5_x64. It fails the md5sum. Because my link is so slow, even a
> torrent
> >>> download will take about 4 days at my current rate.
> >>>
> >>> So, given a corrupted ISO, is there a way to delete the bad parts and
> re-download
> >>> only the good?
> >>>       
> >> Yes. Start the torrent download. Stop it.  Move the .iso you have to where
> >> the new 0 size .iso file was just created by the new torrent.  You want
> >> to overwrite it with the same name.  Now start the torrent again and it
> >> will check the existing file and only download the specific chunks that
> >> fail checksum, not the whole thing.
> >>     
> >
> > Thanks much for the feedback... I have tried this, but so far have not been
> able to
> > get this to work. The ISO I have is slightly larger than the ISO that the
> torrent
> > produces. I tried with ktorrent but it didn't mark *any* chunks as valid.
> Per some
> > searches on Google, I tried using the Azureus client and forcing a re-hash.
> This
> > also showed only a few chunks as valid. I also tried chopping off a few
> bytes off
> > the failed ISO to make it match the size of the valid (sparse) ISO produced
> by the
> > initial torrent download.
> >
> > Not certain if it makes a difference, but the ISO I have is produced from a
> bad DVD
> > by k3b. I think there was corruption in either the original ISO that
> produced the
> > DVD, or else the DVD itself was a failed burn.
> >
> > Oh well... I'm starting to doze off at my keyboard so I'll wrap it up for a
> few. 
> > Thanks again...

I have had several problems with K3B burning an iso - even when the checksum is
equal.  I am told the burn was successful, etc. However, there is nothing on
the disk... blank, but unusable for another try. Changing write speeds and
other settings sometimes works.  Another problem is trying to burn more than
one copy does not work.  Must close app and restart to burn successive copies.
(Using Mepis6.5)  I have not taken time to load a different distro to isolate
problem further (just waste DVDs or CDs till I get it right).

I am on vacation next week, perhaps that will give me time to do some checking.
sw