grub-install fails due to wrong target disk

["Thomas H." <thomas@alternize.com>]

hi

i'm trying to install debian gnu/kfreebsd on a sun x4100 server with two 
sas controllers and an attached j4200 JBOD storage. the disk layout on 
the server is as following:

2x LSI SAS controllers:
- SAS1064 (Bus 02, Dev 03, Fnc 00)
  - Phy 00: Hitachi 146G SAS Disk (boot drive)
  - Phy 01: Hitachi 146G SAS Disk
- SAS1068 (Bus 02, Dev 01, Fnc 00)
  - Sun J4200 Storage Enclosure
    - 6x Hitachi 500G SATA Disk

the debian installer sees the drives as such:

/dev/da0 = disk01 of the j4200 enclosure
/dev/da1 = disk02 of the j4200 enclosure
/dev/da2 = disk03 of the j4200 enclosure
/dev/da3 = disk04 of the j4200 enclosure
/dev/da4 = disk05 of the j4200 enclosure
/dev/da5 = disk06 of the j4200 enclosure
/dev/da6 = internal disk 1 (boot drive)
/dev/da7 = internal disk 2

i selected /dev/da6s1 as the zfs root partition. unfortunately, during 
grub2 installation, the installer tries to setup grub in /dev/da0 
instead of /dev/da6, which fails. instead of

  grub-install --no-floppy --force "/dev/da0"

it should use

  grub-install --no-floppy --force "/dev/da6"

is there a way to run grub-install manually from a 2nd console during 
the installation, or any other way to get grub2 installed on /dev/da6?

thanks,
thomas