X-Recipient: archive-cygwin AT delorie DOT com X-Original-To: cygwin AT cygwin DOT com Delivered-To: cygwin AT cygwin DOT com DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 2244F3951C78 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=cs.umass.edu Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=moss AT cs DOT umass DOT edu Subject: Re: [cygwin] DD bug fails to wipe last 48 sectors of a disk To: Hashim Aziz , cygwin References: <1d1801d64677$bea56050$3bf020f0$@pdinc.us> <60bf1507-4edb-a03f-ec14-07e1ab7f0d94 AT cs DOT umass DOT edu> From: Eliot Moss Message-ID: <239d7547-efe8-4b59-6f4f-8a387baf8048@cs.umass.edu> Date: Tue, 23 Jun 2020 11:29:45 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: cygwin AT cygwin DOT com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: moss AT cs DOT umass DOT edu Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: cygwin-bounces AT cygwin DOT com Sender: "Cygwin" On 6/23/2020 11:28 AM, Hashim Aziz via Cygwin wrote: > I hadn't checked with 512 byte block sizes because of the amount of time it would have taken, but sure enough have just finished trying with bs=512 and no block size at all (so dd's default block size, which is either 512 or 1024) and although each wipe took over 24 hours, they did indeed wipe all of the sectors. So it seems that there's a bug with regards to how Cygwin handles the last block when a large (i.e. sane) block size is selected, and that this bug doesn't occur on actual UNIX-based systems. Well, that certainly points the finger at last-block handling ... EM -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple