Date: Thu, 13 Jan 2022 08:41:07 +1100 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Roderick <hruodr@gmail.com> Cc: FreeBSD Questions List <questions@freebsd.org> Subject: Re: dd and mbr Message-ID: <20220112214107.GI61872@eureka.lemis.com> In-Reply-To: <f0814445-d026-30-8956-84e36db9b7a6@gmail.com> References: <4af920fc-eff1-a92e-d36e-1ba97079864c@gmail.com> <CAM8r67By518wp_1p9%2BJ5p7CE6Zj1M97Rm%2BaA-CSA-qtSVgyidw@mail.gmail.com> <20220112010402.GG61872@eureka.lemis.com> <f0814445-d026-30-8956-84e36db9b7a6@gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--/GPgYEyhnw15BExa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 12 January 2022 at 9:34:31 +0000, Roderick wrote: > > On Wed, 12 Jan 2022, Greg 'groggy' Lehey wrote: >> As others have said, at the very >> least you should have limited the length, otherwise you would >> overwrite the entire disk, one sector at a time. > > That is what I wanted. I was deleting some old disks. I filled it > with zeroes and not random in order not to make the process > slower. Ah, I guessed wrong. Yes, in that case your sysctl would allow you to overwrite the MBR as well. Even without it, you *would* overwrite the (rest of) the entire disk. > Perhaps there is a faster tool than dd. As others have suggested, use bs=64k. Otherwise dd does an IO for every single sector. The speedup is really in the order of 100x. Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply or reply to the original recipients. For more information, see http://www.lemis.com/questions.html Sent from my desktop computer. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA.php --/GPgYEyhnw15BExa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAmHfSvMACgkQIubykFB6QiN7+gCgi5m1U2VoyzLapTgnljToQTHo JCoAn3VacxhsxND4Mp2HJTctYuE6uJGh =UdyL -----END PGP SIGNATURE----- --/GPgYEyhnw15BExa--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20220112214107.GI61872>