Date: Sat, 12 Nov 2005 01:19:52 +0100 From: Dario Freni <saturnero@freesbie.org> To: Chris Pressey <cpressey@catseye.mine.nu>, current@freebsd.org, geom@freebsd.org Subject: Re: fdisk(8) no longer capable of altering geometry Message-ID: <43753528.7030802@freesbie.org> In-Reply-To: <20051027200448.1ba236fe.cpressey@catseye.mine.nu> References: <20051027200448.1ba236fe.cpressey@catseye.mine.nu>
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My little follow-up to this issue. This bug is quite critical on products using bsdinstaller such as FreeSBIE or pfSense. I heard rumours that PC-BSD also encounter this problem and had to workaround it by sysinstall. Can somebody please take a look at it? Thanks, Dario Chris Pressey wrote: > [this is a follow-up to / correction of my post to geom@ a few days ago, > to which there was no reply] > > Hello, > > It appears that fdisk(8) is no longer capable of altering the geometry > of a disk. (By which I mean, the kernel's idea of the BIOS'es idea of > the geometry, of course.) I'd find it reassuring to know whether or not > anyone else is seeing the same behaviour, before I go the official route > and file a PR. > > Initially I thought that this failure case was only for uninitialized > disks, but I have tried further tests and I can't get fdisk(8) to change > the geometry in any of the cases. These cases are: > > a. uninitialized, totally blank disk (dd if=/dev/zero of=/dev/ad1 ...) > b. initialized disk with FreeBSD (or any other OS) installed on it > c. same as b, but with its root partition mounted on /mnt > d. the disk containing the currently booted FreeBSD system > (mounted on /, of course) > > In each of these cases, I tried a sequence like the following: > > fdisk -BI ad1 > fdisk -u ad1 > <when asked if I want to change "our idea of what the BIOS thinks", > say yes, and plug in different but compatible values for cylinders, > heads, and sectors/track> > <when asked if I want to write the new partition table, say yes> > fdisk ad1 > <observe that the geometry hasn't changed> > > The behaviour I see is, in summary: > > a & b: fdisk issues the warning "fdisk: Geom not found" which presumably > refers to the fact that there is no GEOM MBR provider for that > disk. It then falls back to the legacy behaviour of raw-writing > the partition table into sector zero of the disk. This does not, > however, trigger an update of the kernel's idea of the geometry. > > c & d: no "Geom not found" warning, but no change in geometry either. > > I don't see this behaviour on DragonFly; cases a and b work as you would > logically expect (as they worked in 4.x, AFAIR, but I have not yet > tested this) where the geometry does get changed, and subsequent runs of > fdisk report the changed geometry. > > In cases c & d, the behaviour is the same as FreeBSD - nothing changes. > This is not too surprising, since the disk _is_ in use - but an error > message would probably make more sense. > > This bug is one of the few remaining things standing in the way of > porting the BSD Installer to FreeBSD. Without some way of altering the > the geometry, it can't install onto a system whose BIOS misreports the > disk geometry. > > My analysis of the problem can be found in my previous post to geom@, > but to sum it up: I think fdisk needs to inform GEOM somehow that the > geometry should be changed. It might need to trigger the creation of a > GEOM MBR provider for the disk before it does so; but I'm not certain of > any of this, since my knowledge of GEOM is slim at best. > > Hopefully someone more familiar with GEOM and such under -CURRENT is > listening and can shed more light on this problem and/or provide a > workaround and/or explain how I'm wrong and show me the right way to do > what I'm trying to do (change geometry) in -CURRENT. > > Thanks for your time, > -Chris > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > -- Dario Freni (saturnero@freesbie.org) FreeSBIE developer (http://www.freesbie.org) GPG Public key at http://www.saturnero.net/saturnero.asc
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