dual-booting with xp

Jerry McAllister jerrymc at clunix.cl.msu.edu
Thu Jan 15 09:34:37 PST 2004

> Hello,
> I am trying to install FreeBSD 4.9 on a machine that already has XP
> installed. It has 3 SCSI drives. I would like to keep XP on the first
> drive, and install FreeBSD on the third drive and make it dual-boot.
> What's the easiest way?
> When I installed, I made a slice on the 3rd disk (using entire disk) and
> created my partitions there. I also selected the FreeBSD bootmanager,
> but it doesn't seem to write to the first disk, so now when I reboot, I
> don't get a bootmanager menu at all, but go right into XP every time.

Well, that is all good, but it sounds like you didn't choose to
install an MBR when you installed FreeBSD.  It asks that on one
of the screens along about the middle of the process.  It offers
three options as follows:

       BootMgr   Install the FreeBSD Boot Manager
       Standard  Install a standard MBR (no boot manager)
       None      Leave the Master Boot Record untouched

You need to install the FreeBSD Boot Manager (or another third party
boot manager) on every disk that will have bootable slices.  That 
includes the first disk that you are leaving MS stuff on.   

The reason is found in the boot process.   Somewhat simplified and
glossed over, it is:   The BIOS runs and runs down its list of
bootable devices in order of the list.  Typically that is 
  1:  Floppy Disk
  2:  CDrom
  3:  Hard disk
      For Hard disk, it is only smart enough to look at the first one.

The BIOS hands over boot control to the first of these devices that it finds 
a boot record on (please pardon the grammar).  If you only have one disk
(the first disk) with one bootable slice (the first slice) you don't need
a Master Boot Record because there is no choice needed to be made.  It just
uses the boot block on that first slice.  But, that is not what you are
trying to do.  You are trying to multi-boot.   So, you need the MBR.

The code in the Master Boot Record on that device does a few things and 
then if it is set up to boot multiple slices, lets you choose which one
of the slices to boot.   Each of those slices needs to have a boot block 
on it.  The boot block on the slice finishes some stuff and starts the
rest of the boot process for whichever OS you have on that slice.

If the Choice is to boot from a disk other than the first one, you have 
to select that device when the MBR offers the choices and then it jumps 
to the MBR on that other disk and gives you a choice of bootable slices
on that drive.   So, you need the MBR on each disk with bootable slices
along with the OS boot block.

The FreeBSD MBR will work quite fine.  It is a very small one and as such 
doesn't allow you to customize the displays it shows up for the choices.
Typically it recognizes and displays meaningful text for FreeBSD and LINUX
but puts either '???' or 'DOS' for the Microsloth "systems" no matter
what they are.   But, as long as you don't care about how pretty it is
it works just fun to select them.   I am currently typing on a machine
that is dual booted with XP and FreeBSD 4.9.   The MBR offers choices
of ???, DOS and FreeBSD.   The ??? is a Dell diagnostic slice, the DOS
is the XP and, of course, FreeBSD is FreeBSD.

But, if you want, you can install one of the other third party Master
Boot Records such as Grub if you like.   There are a bunch of then with
varying ease of use and varying size and prettiness.


> Thanks,
> Duane
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