how does update-grub choose the root filesystem

[Alan Chandler <alan@chandlerfamily.org.uk>]

I am trying to figure out how to move my current rootfs to raid1 (its 
just a partition at the moment).

The plan is to make a a raid device, copy the current root fs in to it - 
but I then need to tell grub to set up this up as the root for the boot.

How do I do this?

--
Alan Chandler
http://www.chandlerfamily.org.uk