BootBlocks.

[talon at lpthe.jussieu.fr]

walt wrote:

> talon at xxxxxxxxxxxxxxxx wrote:
>> Max von Seibold wrote:
>> 
>>> Hello,
>>>
>>>
>>> Does anyone know of any documentation, or howto's on configuring
>>> bootblocks. I have two hard drives in my tower and have DragonFly on
>>> one. I want to install debian on the second. I am familiar with GRUB but
>>> cannot find anything when I google Bootblocks.
>> 
>> Put something like this in your grub menu.lst
>> 
>> # This is to boot FreeBSD
>> title           FreeBSD
>> root            (hd0,3)
>> savedefault
>> makeactive
>> chainloader     +1
>> boot
> 
> The method above will work, but *only* if the bootblock is
> installed properly -- and I think the installation of the
> bootblock is the part that Max is confused by.
> 
> I deal with bootblocks by ignoring them completely :o)

Yes, as far as i know the bootblocks are *always* installed by
the disklabel that occurs at the beginning of installation. However 
you have the choice of installing or not the booteasy MBR, and i supposed
that the original author was speaking of that. Anyways, to unconfuse
the poster, the command to install bootblocks in Dragon or FreeBSD are
disklabel -B or bsdlabel -B  acting on the appropriate *partition* and
boot0cfg -B acting on the appropriate *disk* to install the booteasy MBR.
For example
disklabel -B ad0s1a
boot0cfg -B ad0
Needs probably to be run from a live cdrom on FreeBSD-5,6 due to the GEOM
protection on such stuff.
As far as i remember the commands are different on OpenBSD.


> 
> Grub will use the bootblock if you want (using the method
> above) but will also bypass the bootblock completely and
> load /boot/loader directly from the DragonFly filesystem:
> 
> root  (hd0,3a) #note: '3a' points to the /root partition
>                  #rather than the bootblock!
> kernel  /boot/loader  #'loader' then loads the real kernel

This works fine if /boot/loader is not living on an UFS2 filesystem
or if you have a recent grub which knows how to read UFS2. The grub which
comes with Debian Sarge does not, for example. This is the reason why i
showed the trivial method which always works, in fact the same as for
Windows.



-- 
Michel Talon