How to boot from a slice other than "a"?

[Wojciech Puchar]

> Filesystem     Size    Used   Avail Capacity  Mounted on
> /dev/da0s1a    248M    180M     48M    79%    /
> /dev/da0s1h     14G    496M     13G     4%    /mnt
>
> /dev/da0s1h has an exact copy of /dev/da0s1a using dump/restore.
>
> I want to configure things so that the next time I reboot it will 
> automatically boot from /dev/da0s1h without me having to do anything (since 
> it's remote I can't interrupt the boot process).
>
> I know I need to modify fstab on da0s1h.  And if I was on the console I'd 
> interrupt the boot process and type in 0:da(0,h)/boot/loader, but I'm not.

are you actually interested of running /boot/loader from partition h or 
mounting root at /dev/da0s1h

if second - add:

vfs.root.mountfrom="ufs:da0s1h"

if first - i don't know :)