Re: Default number of overwrites in shred

[James Youngman]

On 5/3/07, Peter Eckersley <address@hidden> wrote:

> We're certainly working on making sure that userspace chattr()s the
> attribute.  Apparently, for many journalling filesystems (ext3 and maybe
> Reiser, IIRC), shred should still work pretty well as-is -- I guess
> that's because the filesystem promises metadata consistency, not data
> consistency.  For the others, we can certainly ping the developers about
> it.  We could potentially work on patches too, but that's less likely
> unless there's an obvious case where the patch would make a lot of
> real-world difference.

There is a very interesting presentation by Wietse Venema which
discusses this in detail (and, sadly, demonstrates that it is much
harder to do this reliably that one might think).
I can't find a link to the talk but there is an HTML version of it in
the Google Cache at

http://66.102.9.104/search?q=cache:fNI_tJkUHzIJ:www.hack.lu/images/8/80/Venema.ppt+Venema.ppt&hl=en&ct=clnk&cd=3

I think his comments about this relate mainly to ZFS and ext3, though.

James.