Create a file /grub/menu.lst with this content:
In this example FreeBSD is installed in the first partition slice, and NetBSD in the second one. The default OS to boot is the second one, NetBSD. The timeout to boot is 5 seconds.
After this type in a terminal:
grub –no-floppy –no-curses
This will open a shell for grub commands. Simply type:
‘root (hd0,1,a)’ means the grub root directory. In my case I installed Grub from NetBSD. NetBSD is installed in the second partition slice, and grub is inside it, so ‘root’ must be the second partition slice.