address@hidden: Re: security and journaling]

[Scott McDermott]

This from one of the XFS authors.  I believe the reason is because XFS
is metadata-only so there isn't any journalled data; overwrites of data
blocks don't move anything.  I believe this is true of JFS and ReiserFS
as well but should be confirmed.  The only FS I know of for GNU OSes
that can journal data is ext3, and even there the common journalling
option is metadata-only.

----- Forwarded message from Steve Lord <address@hidden> -----

From: Steve Lord <address@hidden>
Subject: Re: security and journaling
To: Ray Muno <address@hidden>
Cc: address@hidden
X-Mailer: Ximian Evolution 1.0.8 
Date: 30 Sep 2002 14:29:27 -0500

On Mon, 2002-09-30 at 14:18, Ray Muno wrote:
> SHRED(1)                       FSF                       SHRED(1)
> 
> NAME
>        shred  -  delete  a file securely, first overwriting it to
>        hide its contents
> 
> SYNOPSIS
>        shred [OPTIONS] FILE [...]
> 
> ...stuff deleted
> 
>        CAUTION:  Note  that  shred  relies  on  a  very important
>        assumption: that the filesystem overwrites data in  place.
>        This  is the traditional way to do things, but many modern
>        filesystem designs do not satisfy  this  assumption.   The
>        following  are  examples  of filesystems on which shred is
>        not effective:
> 
>        * log-structured or journaled filesystems, such  as  those
>        supplied with
> 
>               AIX and Solaris (and JFS, ReiserFS, XFS, etc.)

If shred just overwrites in place it will be effective with XFS,
that man page is wrong.

Steve



-- 

Steve Lord                                      voice: +1-651-683-3511
Principal Engineer, Filesystem Software         email: address@hidden



----- End forwarded message -----

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