Booting FreeBSD-5.3 from NTLDR

[Mark Ovens]

Loren M. Lang wrote:
> On Mon, Jan 31, 2005 at 02:16:25PM +0400, Rakhesh Sasidharan wrote:
>> Thanks for that link! I had read that part of the handbook a long time
>> ago, and that's how my ideas of boot0 and boot1 and etc etc had gotten
>> clear. Glad to see it once again -- in the context of my question! :))
>> 
>> So what I understand now is -- copying boot0 over to c:\bootsect.bsd
>> will *not* work. Which explains why my MBR got messed up when I tried
>> booting FreeBSD this way. :(
>> 
>> But I'm still confused. How do I install boot0 using sysinstall? As
>> far as I remm, sysinstall gives three options -- (a) leave the MBR
>> untouched, (b) put a standard MBR, and (c) install BootEasy. My
>> understanding is that option (b) copies boot0 to the MBR, and this
>> that is what I had chosen while installing FreeBSD. How does one copy
>> boot0 to a file using sysinstall??
> 
> I think option b is actually /boot/mbr and BootEasy refers to
> /boot/boot0.  They are two different boot loaders, mbr being a very
> simple one with no configuration.  I think fdisk -B is used to install
> /boot/mbr to the mbr of a harddisk and boot0cfg is used to install
> BootEasy.
> 

I rewrote that section of the FAQ years ago (around FreeBSD 3.1!!) 
because the previous wording was unclear and I did _exactly_ what 
Rakhesh has done :-(

At that time it was not possible to add FreeBSD to the NTLDR menu if 
FreeBSD was on a _different disk_ so you had to either use the FreeBSD 
boot menu or put the FreeBSD root partition on the same disk as NT 
(which usually required a BIOS that could boot beyond the first 1024 
cylinders) or use the FreeBSD boot manager (which used /boot/boot0).

This is what I have done ever since. As I only have a single user set up 
in XP it doesn't show the NTLDR menu so you don't have to go through two 
boot menus, just the FreeBSD F1/F5 choice.

Caveat: Things have no doubt changed since then so it may now be 
possible to add FreeBSD to the NTLDR menu with FreeBSD on a different 
disk, but I've never investigated it as I am happy with the solution I use.

HTH

Regards,

Mark

>> 
>> 
>> On Mon, 31 Jan 2005 08:44:23 +0000, Mark Ovens <marko at freebsd.org> wrote:
>> > Rakhesh Sasidharan wrote:
>> > >> No, boot0 is just a normal file that is 512 bytes long.  There is
>> > >> nothing special about it.  In it is a bootloader program that can be
>> > >> used to boot FreeBSD, and if you run it during boot, it will read the
>> > >> partition table and look for all OSes.  I think it will modify the
>> > >> partition table, though, marking the last OS you booted into, but that's
>> > >> the program running doing that, the file itself is harmless.
>> > >
>> > > Ok. I must have used some other command then, which resulted in my
>> > > first disk MBR getting over-written ... strange. :-/
>> > >
>> > > By the way, does the fact that NTLDR is on my first disk, while
>> > > FreeBSD (and hence its MBR boot0) is on my second disk complicate
>> > > matters? I mean, you mention boot0 will modify my partition table to
>> > > reflect which OS was booted last -- will it by any chance modify the
>> > > partition table on the first disk and hence mess it?
>> > >
>> > >
>> > 
>> > Yes and yes,
>> > http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/disks.html#NT-BOOTLOADER
>> > 
>> > Regards,
>> > 
>> > Mark
>> > 
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>> > 
>> 
>> 
>> -- 
>> 				-- Rakhesh
>> 				   rax at rakhesh.com
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