Hi,
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
resp.
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.