Date: Tue, 22 Dec 2009 15:11:43 +0100 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: "James R. Van Artsdalen" <james-freebsd-current@jrv.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Some notes on RootOnZFS article in wiki Message-ID: <86my1b5c9s.fsf@ds4.des.no> In-Reply-To: <4B30CCB3.1090401@jrv.org> (James R. Van Artsdalen's message of "Tue, 22 Dec 2009 07:42:11 -0600") References: <200912210600.46044.mel.flynn%2Bfbsd.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>
next in thread | previous in thread | raw e-mail | index | archive | help
"James R. Van Artsdalen" <james-freebsd-current@jrv.org> 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?86my1b5c9s.fsf>