From owner-freebsd-questions@FreeBSD.ORG Fri Mar 14 15:52:10 2008 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 1DE3A1065678 for ; Fri, 14 Mar 2008 15:52:10 +0000 (UTC) (envelope-from jerrymc@gizmo.acns.msu.edu) Received: from gizmo.acns.msu.edu (gizmo.acns.msu.edu [35.8.1.43]) by mx1.freebsd.org (Postfix) with ESMTP id ED9A58FC16 for ; Fri, 14 Mar 2008 15:52:09 +0000 (UTC) (envelope-from jerrymc@gizmo.acns.msu.edu) Received: from gizmo.acns.msu.edu (localhost [127.0.0.1]) by gizmo.acns.msu.edu (8.13.6/8.13.6) with ESMTP id m2EFqNEV020090; Fri, 14 Mar 2008 11:52:23 -0400 (EDT) (envelope-from jerrymc@gizmo.acns.msu.edu) Received: (from jerrymc@localhost) by gizmo.acns.msu.edu (8.13.6/8.13.6/Submit) id m2EFqMul020089; Fri, 14 Mar 2008 11:52:22 -0400 (EDT) (envelope-from jerrymc) Date: Fri, 14 Mar 2008 11:52:22 -0400 From: Jerry McAllister To: Tektonaut Message-ID: <20080314155222.GF19851@gizmo.acns.msu.edu> References: <47DA5637.7000209@fuckner.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47DA5637.7000209@fuckner.net> User-Agent: Mutt/1.4.2.2i Cc: freebsd-questions@freebsd.org Subject: Re: bsdlabel offset 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: Fri, 14 Mar 2008 15:52:10 -0000 On Fri, Mar 14, 2008 at 11:40:55AM +0100, Tektonaut wrote: > Hi, > > following bsdllabel output caught my attention: > > # size offset fstype [fsize bsize bps/cpg] > a: 2097152 0 4.2BSD 2048 16384 28552 > b: 4194304 2097152 swap > c: 312576642 0 unused 0 0 # "raw" part, don't > edit > d: 33554432 6291456 4.2BSD 2048 16384 28552 > ... > > I created this disk with sade or sysinstall. What I'm not sure > about is that partition 'a' has an offset of 0. With an 8k big > /boot/boot I would guess offset should be 16block large. > > But since the disk is booting, some boot1 loader ist located at > sector 0 (from the beginning of this slice). How is it assured, > that the first block will never be overwritten? Where is boot1 > located, where boot2? > > Comparing the first sector with boot and boot1 differs already > at the first char. (and there were no updates so far) That sector 0 lies outside of the slice block 0. What you are seeing is not an absolute disk offset, but the offset in to the slice. It is possible to create it otherwise but isn't done that way by default. Nowdays, actually a whole track is held out, instead of just sector 0 and that is where some of the fancier MBRs such as GRUB get their extra space to work. But, the standard FreeBSD MBR sticks to the official standard of just one sector - which is why it is so plain vanilla. ////jerry > > > Little bemused regards, > Adam > > -- > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org"