Date: Wed, 9 Sep 1998 09:42:39 -0400 (EDT) From: "Robert G. Brown" <rgb@phy.duke.edu> To: Jim Thompson <jim.thompson@pobox.com> Cc: aic7xxx Mailing List <AIC7xxx@FreeBSD.ORG> Subject: Re: lilo: "not the first disk" Message-ID: <Pine.LNX.3.96.980909092132.14508D-100000@ganesh.phy.duke.edu> In-Reply-To: <199809082251.RAA02777@mail.blkbox.com>
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On Tue, 8 Sep 1998, Jim Thompson wrote: > Thanks for the explanation, but I don't think you understand the > problem. It's not a problem booting, but a problem using lilo to > install the boot record. My system will boot off the SCSI disk just > fine, even with the IDE drive present. The BIOS can be told whether to > boot SCSI-first or IDE-first in a mixed system. > > The problem occurs in running lilo to write the boot record to the SCSI > drive. If the IDE disk is enabled, lilo will report "/dev/sda not the > first disk" when in fact it is. A workaround, but an inconvenient one, > is to disable or unplug the IDE disk, then boot into linux. With the > IDE drive/controller disabled, lilo will install the boot record without > complaint. The IDE drive can then be reenabled, and linux will still > boot off the SCSI system just fine. > > Lilo seems to assume that if an IDE drive is present, then it *must* be > the boot drive. This is not correct. I've built several systems with both IDE and SCSI drives and booted off of either one; the real issue is what is found in the MBR of the drive marked in the BIOS as the primary boot drive, since this is what the BIOS firmware will load to start the boot process. This drive could be a floppy, a CD-ROM, an IDE drive, or a SCSI drive -- it doesn't matter. The problem you encounter PROBABLY has something to do with one of three things. a) The BIOS on your particular motherboard is, uhhm, strange, and automatically puts IDE drives present (if any) ahead of SCSI drives (if any) in the boot list. You "should" still be able to explicitly set the boot drive to be, e.g. -- D: (the second, SCSI disk) even if C: (the first, IDE disk) is present in the system. But maybe not, I dunno. b) ALL Intel boot processes have this nasty leftover limit from the very earliest days of DOS/IBM PC's. It was unfortunately assumed that 10 bits was enough to describe the number of cylinders of any sane hard disk back in the days when bits (in main memory or on disk) were roughly 4000 times more expensive than they are today. My first PC hard disk was 10 MB (1/10 the size of a $100 zip floppy) and cost what, $3000? Can't remember exactly. It might have had 60 cylinders. 1024 looked like infinity. UNFORTUNATELY, this is no longer true; many disks have far more than 1024 cylinders. Linux can cope with this (usually) by remapping the cylinders (dividing by two, for example, until the number falls into range) but MS products often cannot. If your disk was partitioned by MS fdisk, and you are trying to boot a partition containing the MBR that is larger than 1024 cylinders, lilo will barf just as fast as WinX because the cylinder limit is really a firmware-level problem and very difficult to remove. I think that this is documented in the lilo howto or man page. It also doesn't "sound" like your problem, but I thought you ought to be aware of the possibility. c) You could be screwing up lilo.conf, or the like. Again, it doesn't sound like this is likely (you sound like you know what you are doing) but you never know. Be sure you've thoroughly read the man page, the howto, and heck, grab the lilo sources and read over any documentation you can find therein. lilo has a lot of options and most of us (at least myself) tend to find a combination that works for us and only change or add one under duress. Maybe this is duress -- there might be a little used option or configuration note that can help you out. Hope this helps. I think a) is the most likely -- not all BIOS's are as sane as one would like them to be. A lot of them, I think, are still strongly influenced by their PC origins and not really suitable for a workstation. The good news is that if your BIOS/motherboard ARE the problem, hey, decent motherboards cost less than $100 from lots of manufacturers. Throw your old one away (salvaging CPU and memory) and start over -- the money is almost certainly less valuable than the time you've already wasted messing with the problem. rgb Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:rgb@phy.duke.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-aic7xxx" in the body of the message
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