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From: Andrew Morton <akpm@zip.com.au>
To: Jan Hudec <bulb@ucw.cz>
Cc: linux-kernel@vger.kernel.org, Matt Gauthier <elleron@yahoo.com>
Subject: Re: secure erasure of files?
Date: Tue, 12 Feb 2002 12:25:01 -0800	[thread overview]
Message-ID: <3C697A1D.4599DDE@zip.com.au> (raw)
In-Reply-To: <Pine.LNX.4.30.0202121409150.18597-100000@mustard.heime.net> <Pine.LNX.4.33.0202121438560.7616-100000@unicef.org.yu> <20020212165504.A5915@devcon.net>, <20020212165504.A5915@devcon.net>; from aferber@techfak.uni-bielefeld.de on Tue, Feb 12, 2002 at 04:55:04PM +0100 <20020212204710.A7416@artax.karlin.mff.cuni.cz>

Jan Hudec wrote:
> 
> > I don't know if any filesystem currently relocates blocks if you
> > overwrite a file, but it's certainly possible and allowed (everything
> > else except the filesystem itself simply must not care where the data
> > actually ends up on the disk).
> 
> AFAIK, ext2 tries to defragment files when possible.

We wish.

> Thus if the file was
> fragmented and the blocks after some fragment are free, it will use these
> instead of the original ones somewhere far apart.

Nope - if you're overwriting a part of the file which already has
allocated blocks, ext2/3 will use the same blocks.

Of course, the disk itself may decide to go and remap the block
if it decides that part of the media is getting tired.

-

  reply	other threads:[~2002-02-12 20:26 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-02-12 13:12 secure erasure of files? Roy Sigurd Karlsbakk
2002-02-12 13:41 ` Davidovac Zoran
2002-02-12 14:03   ` Padraig Brady
2002-02-12 15:55   ` Andreas Ferber
2002-02-12 19:47     ` Jan Hudec
2002-02-12 20:25       ` Andrew Morton [this message]
2002-02-13  0:03         ` Jeff Garzik
2002-02-13  9:33     ` Helge Hafting
2002-02-13 18:27       ` Mike Fedyk
2002-02-13  0:36 ` Tom Vier
2002-02-13  0:45   ` Jeff Garzik
2002-02-20 15:34 ` Bill Davidsen
     [not found] <200202121326.g1CDQct12086@Port.imtp.ilyichevsk.odessa.ua>
2002-02-12 13:33 ` Roy Sigurd Karlsbakk
2002-02-17 21:19   ` Jan-Frode Myklebust
2002-02-19 12:54     ` Jens Schmidt
2002-02-19 14:24       ` Richard B. Johnson
2002-02-21  2:56         ` Petro
2002-02-21  3:20           ` M. Edward Borasky
2002-02-21 17:01             ` Holger Lubitz
2002-02-26  3:39             ` Petro
  -- strict thread matches above, loose matches on Subject: below --
2002-02-12 21:14 Torrey Hoffman
2002-02-19 14:48 Roy Sigurd Karlsbakk
2002-02-19 17:32 ` Rogier Wolff
2002-02-19 17:59   ` Martin J. Bligh
2002-02-19 18:48     ` Rogier Wolff
2002-02-19 20:01       ` Andreas Dilger
2002-02-19 23:13 ` Roy Sigurd Karlsbakk
2002-02-19 16:19 Jesse Pollard

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