Date: Mon, 15 Apr 2002 23:26:57 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Peter Leftwich <Hostmaster@Video2Video.Com> Cc: "Patrick O'Reilly" <bsd@perimeter.co.za>, Mike Meyer <mwm-dated-1018503724.67c309@mired.org>, mpd <mpd6334@cs.rit.edu>, FreeBSD Questions <FreeBSD-Questions@FreeBSD.ORG> Subject: Re: MBR, mfsroot.flp, handbook, and list fail me! [dnelson] Message-ID: <20020416042657.GC7238@dan.emsphone.com> In-Reply-To: <20020415205617.S24688-100000@earl-grey.cloud9.net> References: <20020406195912.GA63541@dan.emsphone.com> <20020415205617.S24688-100000@earl-grey.cloud9.net>
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In the last episode (Apr 15), Peter Leftwich said: > On Sat, 6 Apr 2002, Dan Nelson wrote: > > > Mike, I must beg to differ : I have recently been trying to get > > > the same thing done. I can confirm that "fdisk -B ad0" is safe, > > > as is "boot0cfg -B", but these install the BSD boot manager, > > > which insists on offereing you a menu during the boot process. > > > Peter's question (and mine too now :) is how to "demote" it to > > > the standard mbr which just boots without pausing? > > fdisk -B -b /boot/mbr ad0 > > Since you are using "ad0" in the command line, must you first `cd > /dev` then run this command? No; fdisk knows that its arguments are devices and will prepend /dev for you. You can give it a full path if you want, though, > > will put a "dumb" mbr on that only knows how to chain to the > > bootblock of the first active partition. > > What does "chain to the bootblock of the first active partition" > mean? Basically, the BIOS searches for the first disk with a valid boot block on block 0 of the media (hard drive or floppy disk). If the boot block also has a partition table, the boot code usually is very simple; it finds the first partition marked active and boots block 0 of the partition. The boot block inside the partition is responsible for finding io.sys (for DOS/win95), or /boot/loader (in FreeBSD's case). This is chaining, where each piece of boot code locates the next one in turn and executes it, until your OS is loaded. http://www.pcguide.com/ref/hdd/file/struct.htm has a good explanation of how it all works. -- Dan Nelson dnelson@allantgroup.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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