From owner-freebsd-questions@FreeBSD.ORG Fri Dec 12 07:29:24 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4CFAE16A4CE for ; Fri, 12 Dec 2003 07:29:24 -0800 (PST) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id 40A1B43D1F for ; Fri, 12 Dec 2003 07:29:23 -0800 (PST) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.12.10/8.12.10) id hBCFTMKV049012; Fri, 12 Dec 2003 09:29:22 -0600 (CST) (envelope-from dan) Date: Fri, 12 Dec 2003 09:29:22 -0600 From: Dan Nelson To: Dru Message-ID: <20031212152922.GP2435@dan.emsphone.com> References: <20031211145245.D637@genisis> <20031211201144.GD75256@happy-idiot-talk.infracaninophile.co.uk> <20031211202155.GK2435@dan.emsphone.com> <20031212084227.Q604@genisis.domain.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031212084227.Q604@genisis.domain.org> X-OS: FreeBSD 5.2-BETA X-message-flag: Outlook Error User-Agent: Mutt/1.5.5.1i cc: questions@freebsd.org Subject: Re: dd of mounted filesystem X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 12 Dec 2003 15:29:24 -0000 In the last episode (Dec 12), Dru said: > On Thu, 11 Dec 2003, Dan Nelson wrote: > > In the last episode (Dec 11), Matthew Seaman said: > > > Remember that dd(1) traverses the block device sequentially, but > > > that most FS accesses are random, so any particular change can > > > span either side of dd(1)'s offset. Also that dd'ing from the > > > block device bypasses the usual machinery for doing file IO -- > > > machinery that is designed under the premise that it will have > > > sole control over what gets read or written where and when. > > > > On current you can get around the consistency problem by dd'ing a > > snapshot of the filesystem, just like dump's -L flag does. > > You mean, run "makesnap_ffs" first? I've been meaning to play with > that one, I'll have to try it out. I don't think that's a standard FreeBSD command; what I was thinking of was something like: mount -u -o snapshot /usr/.snap/snap1 /usr dd if=/usr/.snap/snap1 of=blah bs=64k rm /usr/.snap/snap1 -- Dan Nelson dnelson@allantgroup.com