"secure" file flag?

[StefanEßer]

On 2003-11-23 17:31 +0100, Dag-Erling Smørgrav <des at des.no> wrote:
> Stefan Eßer <se at FreeBSD.org> writes:
> > What I'm suggesting is to have the obliteration implemented as an
> > add on to the dirty buffer flush, with the difference that the 
> > buffer contents is prepared for the next step of the erasure process,
> > written out, and then not declared free but again prepared for the
> > next overwrite pass.
> 
> This next pass won't be until thirty seconds later, so it'll take
> about half an hour to completely obliterate a file.  Furthermore,

These 30 seconds are not a  universal constant and ISTR.

I had in mind, that one obliteration pass is performed. 
After each pass, a cache flush has to be performed, and the 
next pass is performed immediately or only after a brief delay.

I see, that this may cause too many CPU cycles spent traversing
the buffer cache.

> unmounting a file system less than half an hour after a file is
> deleted or truncated will fail, and shutting down will most likely
> leave the file system unclean due to repeated failures to flush the
> dirty buffer list.

Yes, that's why I meant that fsck might be used to trigger the
restart of an erasure process that was not completed due to 
shutdown or a crash. This does obviously no good in case that 
somebody else got hold of your disk, menawhile, but it covers
cases that are not dealt with by a user-land utility (which 
would just be stopped halfway through when the system goes down).

Regards, STefan