From owner-freebsd-hackers Sun Jan 26 02:58:43 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id CAA01837 for hackers-outgoing; Sun, 26 Jan 1997 02:58:43 -0800 (PST) Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id CAA01832 for ; Sun, 26 Jan 1997 02:58:40 -0800 (PST) Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.3/8.6.9) id VAA26848; Sun, 26 Jan 1997 21:51:12 +1100 Date: Sun, 26 Jan 1997 21:51:12 +1100 From: Bruce Evans Message-Id: <199701261051.VAA26848@godzilla.zeta.org.au> To: freebsd-hackers@FreeBSD.ORG, j@uriah.heep.sax.de Subject: Re: fdisk headache Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk >> Boot selectors won't work either. > >Since there's nothing to select from. ;-) >Right now, there are three reasons to still call it ``dangerously >dedicated'': > >. Since the MBR is identical to the BSD bootstrap, there's no room for > things like `nextboot' after the MBR, and you can't replace the MBR > by fancy things like a boot selector. Hence, in a system that is > not FreeBSD-only, you could at best make drives != #0 ``DD'', and > you won't be able to boot select away from that drive once you > switched there. (Normally, booteasy allows to wander around back > and forth through all the drives.) There may be 512(*) sd drives, 512 od drives, 16 cd drives and a small number of wd and fd drives :-). That's a lot to select from. (*) Actually at most 128(**) floppy drives and 128(**) hard drives altogether (because of the BIOS interface limit). (**) Your BIOS may vary. >. Some operating systems might choke on that fdisk table afterwards, > so if you are going to install something else on such a drive later, > it's best do do a ``dd if=/dev/zero of=/dev/rXXX count=100'' before ^^^^^^^^^ > recycling the drive to another task. Should be count=1. If 1 won't work, then 100 may not be enough either, and you'd better know what you are doing. E.g., if there is a FreeBSD slice at offset 100000, then there will be a BSD label at offset 100001, and it should be zeroed to prevent it being resurrected if a BSD slice is created at offset 100000 a year later and the label hasn't been changed. >The plus side is: >... >. The number of BIOS geometry constraints to care for reduces drastic- > ally, so you can usually (*) ignore any geometry issues. > > (*) I.e., the BIOS's geometry idea involves at least 15 sectors per > track, 4 heads, and the root file system is not larger than 30 MB. Actually if the root file system is below cylinder 1024 in the BIOS translation mode. I think the 15 sectors/track limit only applies for floppies. Bruce