Re: How to "blank" / "zero out" / "nullify" a dvd-rw?
On 7/31/07, Thomas Schmitt <email@example.com> wrote:
> > I'm trying to "blank" / "zero out" / "nullify" a dvd-rw that has
> > previously had data written to it, so that I can give that dvd-rw to
> > someone else and they wont see the data. (NB I'm _not_ worried about
> > "magnetic/optical history", the FBI, the CIA etc).
> > Please note that I DO NOT necessarily want to turn the disk back to
> > the way it was when it was still in its plastic wrapper.
> > ...
> > ~# growisofs -Z /dev/hdc=/dev/zero
> > ...
> > :-[ WRITE@LBA=0h failed with SK=5h/ASC=30h/ACQ=05h]: Wrong medium type
> > :-( media is not formatted or unsupported.
> > :-( write failed: Wrong medium type
> > ...
> > ~$ dvd+rw-mediainfo
> > ...
> > Mounted Media: 14h, DVD-RW Sequential
> You got a sequentially written DVD-RW.
> Before you can overwrite its content it needs to be blanked
> dvd+rw-format -blank=full /dev/hdc
> or formatted
> dvd+rw-format -force /dev/hdc
> On occasion of anniversary of libburn revival let me state
> that the equivalent cdrskin commands would be
> cdrskin -v dev=/dev/hdc blank=deformat_sequential
> cdrskin -v dev=/dev/hdc blank=format_overwrite
> Blanking but not formatting can be done with cdrecord and wodim
> cdrecord -v dev=ATA:1,0,0 blank=all
> wodim -v dev=/dev/hdc blank=all
> If you use blank=fast then the media will not be useable for
> /dev/zero as data source unless you specify an image size.
> (I never tried growisofs -use-the-force-luke=tracksize:<number>)
> > But (and this is the strange part), if I format the disk using
> > "dvd+rw-format -blank=full /dev/hdc" (which works), then "growisofs -Z
> > /dev/hdc=/dev/zero" works perfectly THE FIRST TIME - it only fails the
> > second time I try to do it.
> That's because unformatted DVD-RW are much like CD-RW.
> You can write a session to them, leave them open, append
> another session, and so on. But you can re-use them only
> after blanking.
> dvd+rw-format -blank=full brings a DVD-RW into this
> unformatted state. -blank without "=full" does the same as
> cdrecord blank=fast.
> You seem to expect the media to behave like DVD+RW.
> So format it once.
> dvd+rw-format /dev/hdc
> -force should not be needed because it is not formatted.
> But i never tried without -force.
> > is there a way to "blank" / "zero out" / "nullify"
> > a dvd-rw which won't permanently destroy the
> > disk if I do it 20 times?
> (start sarkasm) To my experience, most DVD-RW are destroyed
> before they get into their shrink wrap. (end sarkasm)
> Formatting is needed only once. The media stays overwriteable
> until you deformat it or it finally refuses to work with
> your drive. So there is no problem with 20 times or so.
> Blanking (i.e. deformatting) seems not to be more dangerous
> to the media than overwriting with data. This way or that
> way the media will give up its life early enough.
> I got 3 DVD burners and none of them works well with 4x DVD-RW.
> For repeated backups i only use 4x DVD+RW.
> They get formatted automatically and blanking is not
> applicable to them.
> Have a nice day :)
Wow - that's a lot of information. I can now see that my understanding
(i.e. dvd-rw and dvd+rw were the same) was very wrong!
Thomas, thank you for the info - I really appreciate it. I don't
understand it all now, but I will read it (10 times) and try to
understand this "mode"/"recording strategy" thing better. (I've also
just found http://fy.chalmers.se/~appro/linux/DVD+RW/-RW/ which
explains the same subject, I think)