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Date:      Sun, 8 Feb 1998 21:51:02 -0800 (PST)
From:      Doug White <dwhite@gdi.uoregon.edu>
To:        Werner Koch <wk@isil.d.shuttle.de>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: GRUB and rootdev
Message-ID:  <Pine.BSF.3.96.980208214708.24904N-100000@gdi.uoregon.edu>
In-Reply-To: <19980205103435.60098@isil.d.shuttle.de>

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On Thu, 5 Feb 1998, Werner Koch wrote:

> > you're doing it the wrong way -- you need to hack GRUB to recognize the
> > FreeBSD FS.  FreeBSD does not support any other root filesystem type other
> > than UFS (with exception, but the Linux FS isn't one of them).
> 
> Sure, that't the correct way.  But I like to install FreeBSD first, so I can
> look at it's sources.  The only problem is, that I don't know, how to tell
> the kernel what the rootdev is.  The installation made a custom kernel out
> of kernel.GENERIC and I' can't believe, that it is not possible to set the
> rootdev into that kernel (which boots) - or does the kernel use the device
> from which it is loaded as rootdev?  In that case I really have to patch
> GRUB so it can load the kernel from the freebsd filesystem. 

The installer does not build kernels; it simply writes in the device
configuration set in the boot-time confiuguration utility into the kernel
itself so you don't have to do it again after the install, when it doesn't
come up automatically.

The kernel intuits which disk it's booting from by using some special
magic, somehow translating bios disk number to real-life device number.
It then tries to mount partition a on the device.  Partition a must be a
UFS partition.  To answer the question, it uses the device it was loaded
from.  

> By the way, what is the difference between the FreeBSD filesystem, mentioned
> in the GRUB dox and the one which is used by FreeBSD (GRUB complains that
> it does not know this file system on partion with type a5)

I don't know; I'd have to look at GRUB (which may be stuck in the dark
ages thinking that FreeBSD uses the same ID as other BSDs).  

Doug White                              | University of Oregon  
Internet:  dwhite@resnet.uoregon.edu    | Residence Networking Assistant
http://gladstone.uoregon.edu/~dwhite    | Computer Science Major



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