From owner-freebsd-questions@FreeBSD.ORG Sat Dec 1 20:20:15 2007 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CDBB716A419 for ; Sat, 1 Dec 2007 20:20:15 +0000 (UTC) (envelope-from kdk@daleco.biz) Received: from ezekiel.daleco.biz (southernuniform.com [66.76.92.18]) by mx1.freebsd.org (Postfix) with ESMTP id 6062813C45D for ; Sat, 1 Dec 2007 20:20:14 +0000 (UTC) (envelope-from kdk@daleco.biz) Received: from localhost (localhost [127.0.0.1]) by ezekiel.daleco.biz (8.13.8/8.13.8) with ESMTP id lB1KKDuU006779; Sat, 1 Dec 2007 14:20:13 -0600 (CST) (envelope-from kdk@daleco.biz) X-Virus-Scanned: amavisd-new at daleco.biz Received: from ezekiel.daleco.biz ([127.0.0.1]) by localhost (ezekiel.daleco.biz [127.0.0.1]) (amavisd-new, port 10024) with LMTP id FL0v5-4Bmnqu; Sat, 1 Dec 2007 14:20:08 -0600 (CST) Received: from archangel.daleco.biz (dsl.daleco.biz [209.125.108.70]) by ezekiel.daleco.biz (8.13.8/8.13.8) with ESMTP id lB1KK5rB006764; Sat, 1 Dec 2007 14:20:06 -0600 (CST) (envelope-from kdk@daleco.biz) Message-ID: <4751C1EF.4010206@daleco.biz> Date: Sat, 01 Dec 2007 14:19:59 -0600 From: Kevin Kinsey User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.8.1.2) Gecko/20070418 SeaMonkey/1.1.1 MIME-Version: 1.0 To: stevefranks@ieee.org References: <539c60b90712010929m7fef7020v806eb3c1eb24d066@mail.gmail.com> In-Reply-To: <539c60b90712010929m7fef7020v806eb3c1eb24d066@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: User Questions Subject: Re: using dd to duplicate disks/partitions of slightly different sizes - works? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Dec 2007 20:20:15 -0000 Steve Franks wrote: > I've got two 160GB disks. Different manufacturers, so different # > bytes. One is FreeBSD, the other blank. I'd like to backup my system > for the fastest possible recovery after a crash - move the plug and > power up. I have gmirrored before, but I just wanted to do a quick > dd, since I don't want to abuse my cheapo powersupply (has 4 disks > already on it). > > Two questions: > > (1) If I dd from the smaller to the larger, will it work? What > happens to the extra, say 5MB of unused space - will my partition info > be messed up? > > (2) If I dd from the larger to the smaller (df reports only 50% used > anyway) is there a way to make sure there is no info in the 5MB at the > end that will overflow the smaller, and again, will my partitions be > ok? > > The other option is just to fdisk & label the other disk, then rsync > everything to it. Is that the wiser choice? > > Thanks, > Steve Giorgos Keramidas made a great post dealing with this a while back. Here 'tis, quoted for your enjoyment and potential enlightenment (also quoted is Martin McCormack): ----------------------------------------------- >> It turns out that dd defaults to 512-byte blocks so I didn't >> really need the bs=512, but I am not sure I haven't made some other >> type of mistake. The dd command has been running for about 4 hours on >> a very fast system, with a 1-gig processor, 1 gig of RAM and two 31-GB >> drives. One would think it should have finished by now, but it is >> still running. Is this a valid method of copying the entire contents >> of one drive to another? Thank you. Bah! That's too slow for my taste. I would usually go for a newfs, dump, and restore option. For instance, to create a copy of /usr on a second disk: newfs -U /dev/ad1s1a mount /dev/ad1s1a /mnt dump -0 -a -L /usr | ( cd /mnt ; restore ruvf - ) Copying with dd(1) is not as fast :) ------------------------------------------ HTH, Kevin Kinsey -- There is no royal road to geometry. -- Euclid