Date: Sun, 27 Oct 2002 14:41:22 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Mark Valentine <mark@thuvia.demon.co.uk> Cc: Terry Lambert <tlambert2@mindspring.com>, Julian Elischer <julian@elischer.org>, Poul-Henning Kamp <phk@critter.freebsd.dk>, "M. Warner Losh" <imp@bsdimp.com>, <freebsd-arch@FreeBSD.ORG> Subject: Re: cvs commit: src/lib/libdisk Makefile chunk.c write_alpha_disk.c write_i386_disk.c write_pc98_disk.c Message-ID: <20021027142156.R10013-100000@gamplex.bde.org> In-Reply-To: <200210261352.g9QDqT4V005261@dotar.thuvia.org>
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On Sat, 26 Oct 2002, Mark Valentine wrote: > > From: Bruce Evans <bde@zeta.org.au> > > Date: Sat 26 Oct, 2002 > > Subject: Re: cvs commit: src/lib/libdisk Makefile chunk.c write_alpha_disk.c write_i386_disk.c write_pc98_disk.c > > > On Sat, 26 Oct 2002, Mark Valentine wrote: > > > By the way, FreeBSD doesn't seem to be consistent about which partition it > > > uses, but I've never tried to figure out when it uses partition 1 and when > > > it uses partition 4, though I've seen both occur on disks with only FreeBSD > > > (is it DD mode that makes the difference?). > > > > It is consistent: the first slice with type 0xa5 is mapped to the > > compatibilty slice (except with GEOM of course). > > Sorry, I wasn't talking about the compat slice stuff here, but which slice > FreeBSD uses when you initialize a disk. Sysinstall will obviously use > partition 1 when installing to the whole disk. This isn't very obvious. The standard partition table for zip disks is one undangerously dedicated slice covering the whole disk except the first (nominal) track. It uses partition^Wslice 4. Anyway, this choice should be optional. > In fact what I'm seeing is the "fake" partition table reported for my > DD disks, which uses partition 4 for some reason. So if I were to replace The dangerously dedicated slice uses slice 4 too. I'm no particiular reason. I'm not sure where sysinstall prefers to put undangerously dedicated slices. > my root disk with one which wasn't DD (and if I were using GEOM), I'd > likely have to fix up my fstab after restoring the root file system; > this seems gratuitous. Maybe not. > I'm still a little unclear about the claims that, with GEOM, you can > still use /dev/da0c etc. for DD disks (I'm thinking removable media > such as Jaz disks here). I think they would work. My test system has ata and a zip disk. GEOM broke "disklabel ad0" since ad0 is sliced normally, but not "disklabel afd0" since afd0 is DD. > How does the fake MBR partition table affect this? Don't know, but it should be detected as DD. > > FreeBSD ignores the active partition flag. > > OK. Would it do more harm than good to use this as a hint when locating > the compatibility slice? It would if the boot loader changes it to the boot slice. Some boot loaders have this bug, because some OSes won't boot from non-active slices. I use a boot loader that ignores active flags and boots its own idea of the boot slice. I leave the active flag set for a Windows partition and never set it for a FreeBSD partition. So using it more would be less than useful for me. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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