From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from qmta12.emeryville.ca.mail.comcast.net ([76.96.27.227]:35980 "EHLO qmta12.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479Ab3CRSWZ (ORCPT ); Mon, 18 Mar 2013 14:22:25 -0400 Received: from [192.168.1.23] (unknown [192.168.1.23]) by decaymodealpha.mooo.com (Postfix) with ESMTPSA id 174043D871 for ; Mon, 18 Mar 2013 14:15:17 -0400 (EDT) Message-ID: <514759B5.5000507@lolwut.org> Date: Mon, 18 Mar 2013 14:15:17 -0400 From: Kyle MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: Impossible or Possible to Securely Erase File on Btrfs? Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi, After reading through the btrfs documentation I'm curious to know if it's possible to ever securely erase a file from a btrfs filesystem (or ZFS for that matter). On non-COW filesystems atop regular HDDs one can simply overwrite the file with zeros or random data using dd or some other tool and rest assured that the blocks which contained the sensitive information have been wiped. However on btrfs it would seem any such attempt would write the zeros/random data to a new location, leaving the old blocks with the sensitive data intact. Further, since specifying NOCOW is only possible for newly created files, there seems to be no way to overwrite the appropriate blocks short of deleting the associated file and then filling the entire free filesystem space with zeros/random data such that the old blocks are eventually overwritten. What's the verdict on this? Regards, Kyle