Loader, MBR and the boot process

[Dan Naumov]

On Fri, Jan 22, 2010 at 6:49 AM, Dan Naumov <dan.naumov at gmail.com> wrote:
> On Fri, Jan 22, 2010 at 6:12 AM, Thomas K. <fwd at gothschlampen.com> wrote:
>> On Fri, Jan 22, 2010 at 05:57:23AM +0200, Dan Naumov wrote:
>>
>> Hi,
>>
>>> I recently found a nifty "FreeBSD ZFS root installation script" and
>>> been reworking it a bit to suit my needs better, including changing it
>>> from GPT to MBR partitioning. However, I was stumped, even though I
>>> had done everything right (or so I thought), the system would get
>>> stuck at Loader and refuse to go anywhere. After trying over a dozen
>>
>> probably this line is the cause:
>>
>> dd if=/mnt2/boot/zfsboot of=/dev/"${TARGETDISK}"s1a skip=1 seek=1024
>>
>> Unless by "swap first" you meant the on-disk location, and not the
>> partition letter. If swap is partition "a", you're writing the loader
>> into swapspace.
>>
>>
>> Regards,
>> Thomas
>
> At first you made me feel silly, but then I decided to double-check, I
> uncommented the swap line in the partitioning part again, ensured I
> was writing the bootloader to "${TARGETDISK}"s1b and ran the script.
> Same problem, hangs at loader. Again, if I comment out the swap,
> giving the entire slice to ZFS and then write the bootloader to
> "${TARGETDISK}"s1a, run the script, everything works.

I have also just tested creating 2 slices, like this:

gpart create -s mbr "${TARGETDISK}"
gpart add -s 3G -t freebsd "${TARGETDISK}"
gpart create -s BSD "${TARGETDISK}"s1
gpart add -t freebsd-swap "${TARGETDISK}"s1

gpart add -t freebsd "${TARGETDISK}"
gpart create -s BSD "${TARGETDISK}"s2
gpart add -t freebsd-zfs "${TARGETDISK}"s2

gpart set -a active -i 2 "${TARGETDISK}"
gpart bootcode -b /mnt2/boot/boot0 "${TARGETDISK}"


and later:

dd if=/mnt2/boot/zfsboot of=/dev/"${TARGETDISK}"s2 count=1
dd if=/mnt2/boot/zfsboot of=/dev/"${TARGETDISK}"s2a skip=1 seek=1024


Putting the swap into it's own slice and then putting FreeBSD into
it's own slice worked fine. So why the hell can't they both coexist in
1 slice if the swap comes first?


- Dan Naumov