Disk Geometry

ras bsd ras.bsd at gmail.com
Thu Feb 28 20:30:22 UTC 2008

On 28/02/2008, Jerry McAllister <jerrymc at msu.edu> wrote:
> On Thu, Feb 28, 2008 at 12:48:37AM +0100, ras bsd wrote:
>  > Hello list, this is my first post here.
>  >
>  > My problem is:
>  >
>  > I've installed the OS in my laptop in this order, Win XP and Debian
>  > GNU/Linux. I'm trying to dive into the freebsd world from many years
>  > in GNU/Linux. When i start the installation, when i have to enter in
>  > the disk partition section an error appears saying that the disk
>  > geometry is not valid and, anyway, I can not see the free disk space
>  > that i left free after the other OS. My scope is keep working the
>  > three OS.
>  > How can i know the correct disk geometry? What am i doing wrong?
> Well, I don't know why it does not see the free space unless you
>  are looking in the wrong step.   There is often confusion by new
>  users who come from the MS world because FreeBSD uses the term 'slice'
>  and MS uses the term 'primary partition' to refer to the same thing.
>  Due to ancient conventions in Bios and etc, there can be up to 4 slices
>  (or primary partitions) on any physical disk.
>  Lunix has its own notion of extended partition as well.  Don't try
>  to use that for FreeBSD.
>  FreeBSD must be installed/built in a free slice (primary partition by
>  MS vocabulary).   It cannot be put in some extended partition space.
>  It is possible that you have already used up the 4 slices if the laptop
>  manufacturer put a diagnostic utility slice on the drive.  That is
>  normally hidden from MS, but will show up to FreeBSD.  If that is true,
>  and you have used up the number of slices, then FreeBSD will not allow
>  you to add any.  You will need to use a tool such as 'gparted'  or
>  Partition Magic to shuffle things around and maybe squeeze the other
>  slices and even nuke one.
>  Then FreeBSD uses the term 'partition' to refer to the subdivisions
>  of a slice.  MS has some things called extended partitions which are
>  not the same thing at all.
>  Anyway, the point where you first need to see the free space is in
>  the step dealing with the slices which is done with fdisk(8).
>  As for the disk geometry issue, it normally does not matter.  That
>  is the BIOS complaining.   You want to just let it go ahead and
>  build things and try to ignore that error message.   Once it gets
>  past loading the boot sector from a slice, FreeBSD no longer used
>  the BIOS.   It handles everything itself.
>  There are exceptions to this response, but go ahead (once you get the
>  free space issue figured out) and try it and see if it works.  It
>  won't hurt anything and if it works, you're home free.  If it doesn't
>  then you have some more exploring to do.    I am not quite sure what
>  because although I have frequently seen that message - almost all
>  the time, I have never had it not work to just go ahead and slice,
>  partition and build and ignore the message.  That is with both IDE(SATA)
>  and SCSI(SAS).
>  So, your real problem is finding that elusive free slice space or
>  freeing up a slice number to use for it.
>  Good luck,
>  ////jerry
>  >
>  > Mi laptop is Intel Core2 Duo and the Hard Disk is SATA 200 Gb Toshiba
>  > MK2035GSS-(S1).
>  >
>  > Thank you.
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Thank you very much Jerry.

It was the problem, I had the free space in a extended partition made
of ext3fs Linux. The solution was move the space and leave that
partition totally unalocated. After that everything was ok with the
installation. I'm on it.

Thank you.

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