Hosed my MBR?

[Jerry McAllister]

> 
> Hello,
> 
> I'm in a bit of a mess here.  I've got an Asus P4C800-E Deluxe
> motherboard with two on-board SATA RAID controllers, an Intel MatrixRAID
> (ICH5R) and Promise Fasttrak (PDC20378).  My BIOS allows me to boot
> from either the Promise or the Intel controller.
> 
> The PDC20378 runs two drives in a RAID0 configuration booting FreeBSD
> 6.0-STABLE.  The entire drive (ar0) is dedicated to FreeBSD and I have
> the boot-manager installed.   The ICH5R also runs two drives in a
> RAID0 for Windows XP.  I allocated roughly 25% of the drive (ar1) to
> Windows NTFS (ar1s1) and left the remaining disk open. 
> 
> Now that 6.x supports the ICH5R I decided to use the leftover disk (ar1)
> for a FreeBSD slice.  I used sysinstall's fdisk to create the slice in
> the unused portion of the disk.  I successfully committed the changes.  I
> then used # newfs /dev/ar1s2 to create a file-system and it went fine.
> 
> The problem is, now, when I attempt to boot off the Intel controller, I
> get a FreeBSD boot load failure:

> ---
> 
> Invalid Partition
> Invalid Partition
> 
> No /boot/loader
> 
> FreeBSD/i386 boot
> Default: 0:ad(0,a)/boot/kernel/kernel
> boot:
> 
> Invalid partition
> No /boot/kernel/kernel
> 
> FreeBSD/i386 boot
> Default: 0:ad(0,a)/boot/kernel/kernel
> boot:
> 
> ---
> 
> So it would seem I hosed my MBR.  The question is, how did I do it and
> how do I fix it?  I would think that when I choose to leave the MBR
> untouched in sysinstall, that it would do just that.  
> 
> I cannot use the old DOS boot floppy trick of:  fdisk /MBR as DOS will
> not recognize my Intel controller.  Windows installation media is
> equally clueless.  I want to be very careful here so as not to render my
> entire system useless.  A thought occurred to me that I might be able to
> get a MBR from another Windows box 
> 
>    freesbie# dd if=/dev/ad0 of=/mnt/nfs/tmp/XP.mbr bs=512 count=79
>    hosedbox# dd if=/mnt/nfs/tmp/XP.mbr of=/dev/ar1 bs=512 count=79
> 
> and write that over my bad MBR.  Does that make sense?  Is there a
> "better" way?

Well, the install CD is also the fixit CD.  You can try booting from
it and choosing the shell and then trying to run the fdisk from that
environment to replace the MBR.  

I have done that for people who have hosed their MBR on machines with 
Ghost - even their XP only, no FreeBSD, systems, using the FreeBSD fixit, 
I ran fdisk and replaced the MBR with the FreeBSD MBR and it worked just fine.

Now, if that is not really the problem, of course that won't fix
anything.  But it shouldn't hurt either.   And you could really mess things
up with the dd.

Good luck,

////jerry
> 
> 
> -- 
> Regards,
> Doug
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