From owner-freebsd-questions Mon Jan 13 16:40:21 2003 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 024D537B401 for ; Mon, 13 Jan 2003 16:40:20 -0800 (PST) Received: from sccrmhc02.attbi.com (sccrmhc02.attbi.com [204.127.202.62]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6E08B43F7B for ; Mon, 13 Jan 2003 16:40:18 -0800 (PST) (envelope-from swear@attbi.com) Received: from localhost.localdomain ([12.242.158.67]) by sccrmhc02.attbi.com (sccrmhc02) with ESMTP id <2003011400401200200mnl7qe>; Tue, 14 Jan 2003 00:40:12 +0000 Received: from localhost.localdomain (localhost [127.0.0.1]) by localhost.localdomain (8.12.6/8.12.5) with ESMTP id h0E0jPm9018927 for ; Mon, 13 Jan 2003 16:45:25 -0800 (PST) (envelope-from swear@attbi.com) Received: (from jojo@localhost) by localhost.localdomain (8.12.6/8.12.5/Submit) id h0E0jEcU018922; Mon, 13 Jan 2003 16:45:14 -0800 (PST) (envelope-from swear@attbi.com) X-Authentication-Warning: localhost.localdomain: jojo set sender to swear@attbi.com using -f To: freebsd-questions@freebsd.org Subject: Dangerously dedicated vs. fully dedicated, etc. From: swear@attbi.com (Gary W. Swearingen) Date: 13 Jan 2003 16:45:14 -0800 Message-ID: Lines: 49 User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.1 (Cuyahoga Valley) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG I'm having trouble understanding a couple parts of the "disklabel" manpage related to dangerously/fully dedicated disks. The "BUGS" section has this paragraph: For the i386 architecture, the primary bootstrap sector contains an embedded fdisk table. The disklabel utility takes care to not clobber it when installing a bootstrap only (-B), or when editing an existing label (-e), but it unconditionally writes the primary bootstrap program onto the disk for -w or -R, thus replacing the fdisk table by the dummy one in the bootstrap program. This is only of concern if the disk is fully dedicated, so that the BSD disklabel starts at absolute block 0 on the disk. 1) Can anyone explain that last sentence to me? Shouldn't that "is only of concern" instead be "is not of concern", reversing the sense? 2) Is a "fully dedicated" disk exactly the same as a "dangerously dedicated" disk? If not, what's the difference? Can one use a disk (or a slice) which has no space reserved for stage 1 & 2 boot records, say, for a non-bootable disk? I know no way to disklabel one that way. 3) Is "block 0" exactly the same as "sector 0"? 4) Shouldn't "BSD disklabel starts at absolute block 0" be "FreeBSD stage 1 boot record starts at sector 0"? The disklabel immediately follows the stage 1 boot record, right? So it would be "block 1"? Under "Writing a standard label", the manpage says: PC-based systems have special requirements in order for the BIOS to properly recognize a FreeBSD disklabel. Older systems may require what is known as a ''dangerously dedicated'' disklabel, which creates a fake DOS partition to work around problems older BIOSes have with modern disk geometries. 5) What's "fake DOS partition"? DD disks don't have partitions. Is it just trying to not bother saying that it fills in the MBR partition table as if there was at least one slice which the DD MBR will ignore. 6) Why is the problem limited to older systems? Don't new BIOSes check for a normal-looking partition table? 7) Isn't the first sentence wrong? BIOS don't look for disklabels, do they? The special requirements are in order for the BIOS to find the FreeBSD stage 1 boot record, no?. (And the FreeBSD installer doesn't satisfy the requirements for non-DD disks (as I read the FAQ's DD answer). I can't imagine why not. Older systems with a standard MBR boot any active slice (even FreeBSD) without problems, no?) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message