From owner-freebsd-current@FreeBSD.ORG Tue Dec 22 14:11:45 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5C574106568B for ; Tue, 22 Dec 2009 14:11:45 +0000 (UTC) (envelope-from des@des.no) Received: from smtp.des.no (smtp.des.no [194.63.250.102]) by mx1.freebsd.org (Postfix) with ESMTP id 1BEEA8FC1B for ; Tue, 22 Dec 2009 14:11:44 +0000 (UTC) Received: from ds4.des.no (des.no [84.49.246.2]) by smtp.des.no (Postfix) with ESMTP id 154F21FFC1E; Tue, 22 Dec 2009 14:11:43 +0000 (UTC) Received: by ds4.des.no (Postfix, from userid 1001) id C763D84531; Tue, 22 Dec 2009 15:11:43 +0100 (CET) From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= To: "James R. Van Artsdalen" References: <200912210600.46044.mel.flynn+fbsd.current@mailing.thruhere.net> <20091221150514.GB75616@roberto-al.eurocontrol.fr> <4B2F9877.70201@jrv.org> <867hsf6xhh.fsf@ds4.des.no> <45929E18-EA48-4340-9954-683FF06B180B@exscape.org> <86r5qn5gem.fsf@ds4.des.no> <4B30CCB3.1090401@jrv.org> Date: Tue, 22 Dec 2009 15:11:43 +0100 In-Reply-To: <4B30CCB3.1090401@jrv.org> (James R. Van Artsdalen's message of "Tue, 22 Dec 2009 07:42:11 -0600") Message-ID: <86my1b5c9s.fsf@ds4.des.no> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.95 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: FreeBSD Current Subject: Re: Some notes on RootOnZFS article in wiki X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Dec 2009 14:11:45 -0000 "James R. Van Artsdalen" writes: > It definitely breaks things *when booting* to depend in any way on a > partition table since there may not be one. By the mid 90's nearly > every OS was putting in at least dummy partition tables for the same > reason GPT does - to lessen the risk of accidental clobbering of the > disk - but that's just a convention. I'm sure there are still a few > customized VAR-things out there that don't bother with a partition table. I can assure you that Windows does not put in a dummy partition table, and will not boot if the partition is not active. I can also assure you that the BIOS on my current laptop (ThinkPad T60) *does* care about the partition table, because the BIOS boot menu has an option to launch the rescue & recovery utility, which is located on a DOS partition at the end of the disk (although the BIOS works fine if the R&R partition is missing) > A number of vendors have taken to putting "hidden" system partitions on > the disk with various utilities that can be run via a hotkey press > during POST. These schemes have to use MBR-like code from the BIOS ROM > to boot their system partition and that pseudo-MBR must read and > interpret the partition table to find the system partition. But during > system boot itself the MBR sector is read and if the last word in that > sector is 0xAA55 then the BIOS executes the MBR code blind as to what is > on the disk. It's the MBR code that's read from the disk that scans the > partition table, if there is one. I can't quite parse that. The R&R partition on my T60 is not hidden in any way. > There were attempts for a time to check for boot sector virii before > booting but those were always so problematic that I never did that, and > I don't the the other main BIOS teams did it either. I've had machines that had a BIOS option to check if the boot sector had been modified and warn the user before booting. It worked just fine. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no