Subject: Re: start of the partition c
To: <>
From: David Laight <>
List: netbsd-users
Date: 07/16/2004 19:42:48
On Fri, Jul 16, 2004 at 05:56:03PM +0200, Lubos Vrbka wrote:
> hi guys,
> i've got another question. i'm adding new harddrive (ide) to my i386 
> box. i've got question about partitioning. my "d" partition on this 
> drive starts at 0s and ends at the very end of the drive, but where 
> should partition "c" start? it starts on sector 63 on the first disk 
> containing system, but disklabel offered me 0s for the new drive. i used 
> it and the drive seems to work ok, but i'm not sure whether this setup 
> is ok.

It will cause least confusion to any other OS that might find the disk
if the disk has an mbr (aka fdisk) partition table, and that any NetBSD
filesystems are entirely with the NetBSD (type 169) mbr partition (or
some other mbr partition).
Some system BIOS may also refuse to boot disks that don't look 'right'.

As to what you have done:

I assume you have defined an mbr partition from sectors 63 onwards
(since that it what defines 'c'), in which case the NetBSD disklabel
will have been written into sector 65.

If you initialised an ffsv1 filesystem starting in sector zero, then
it will have written it's superblock at 8k [1] - straight over the disklabel.
I suspect it doesn't work....

Having overwritten the disklabel, the kernel will 'magic one up' when
the disk is opened.  This will contain 'c' (from the mbr) and 'd' but
probably nothing else (it might contain 'a' - also covering the whole disk).

It is possible to use all of the disk for a filesystem - but it is best
done by making the mbr partition cover the entire disk (or just zero
sector zero), and have the NetBSD label in sector 1.


[1] unless you make the blocksize 16k or greater.

David Laight: