grub install, then switch harddrives

[batkiwi]

I have a computer I'm "upgrading" to gentoo.

2 HD's:
hda which is my big drive, which has an LFS 3.2 system on it
hdb which was blank (20gig), now had gentoo on it running in chroot.

What I hope to do is copy everyone's /home to hdb, reboot into gentoo, copy /home to the big drive, change fstab to mount /home from hda1, then reboot. I have all of this figured out, and have done it many times before with no problem.

My problem is that I plan to swap hda and hdb, and need grub to work. (i like having my system drive hda).

So when I install grub, it will go onto hdb, but when it reboots, it will be hda.

Do I do:
root(hd0,0)
setup(hd1)
(ie install into hd1, but tell that bootloader to go to hd0 since tha'ts what it will be when I reboot)

or

root(hd1,0)
setup(hd1)

I know setup will go onto hd1, but don't know what to specify root as. I know lilo writes that stuff at "install" time (hence having to rerun lilo when you change kernel) but don't know how grub works

[cyrillic]

You could use GRUB's device map feature so that GRUB will be installed correctly to the future (hd0) rather than the present one :