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SubjectRe: preventing undeleting on ext2?
FromAndi Kleen <>
Date04 Jan 1997 05:07:33 +0100
"Stephan K. Zitz" <zitz@io.com> writes:

> On Fri, 3 Jan 1997, Andrew E. Mileski wrote:
> 
> > > It used to be possable to prevent undelete by deleting a file, over
> > > writing it byte for byte, and deleting that file. But it seems that this
> > > no longer works under the newer kernels. How could one be prevented for
> > > undeleting files under the newer kernels? And info would be greatly
> > > appreaciated. Thanks.
> > I'd be amazed if that ever worked.
> > You have to over-write the file, and sync, _before_ you unlink it.
> > You can hold a file open THEN unlink it though - this will prevent
> > anyone else from opening the file while it is being over-written.
> > As long as a file is held open, its data is kept intact after an unlink.
> 
> I'm not sure of the status of it, but didn't the attribute 's' (see
> chattr(1)) accomplish this?
> 
> ie, 
>   chattr +s filename

It used to work, but in 2.0.x kernels I find this in linux/fs/ext2/truncate.c:

/*
 * Secure deletion currently doesn't work. It interacts very badly
 * with buffers shared with memory mappings, and for that reason
 * can't be done in the truncate() routines. It should instead be
 * done separately in "release()" before calling the truncate routines
 * that will release the actual file blocks.
 *
 *		Linus
 */
and the relevant code is commented out.

-Andi

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