Since this whole thing didn’t work out for me right away, I’ll try to write down an algorithm of actions for those who add FreeBSD to GRUB2 for the first time.
Provided that we already have Ubuntu.

1. When installing a freak, when it offers to install the bootloader, you need to select BootMgr
http://www.freebsd.org/doc/en/books/handbo...ll/boot-mgr.png

2. After installing the frach, we restore the hornbeam through the LiveCD Ubuntu
http://ru.wikibooks.org/wiki/Grub_2#.D0.92...2_.D1.81_LiveCD

3. We go to the already installed ubuntu and find out on which section the frayka is.
To do this, in the terminal, type:
$ sudo fdisk -l
I have it on sda3 (remember!).

4. Open nautilus with superuser privileges.
Hit Alt + F2 and write
gksu nautilus
We find the file /etc/grub.d/40_custom, open it, delete nothing and add text to the end of the file

menuentry "FreeBSD 8.2" {
insmod ufs2
set root = (hd0,3)
chainloader +1
}

The last line should be blank. And save the file.
In this case, you need to understand how to correctly indicate the section of the hornbeam where the frach is located. Since I have it on sda3, I wrote "set root = (hd0,3)". That is, the hornbeam begins to count physical disks from zero, and the sections inside the screw from one. It would also be more correct to write "set root = (hd0,3, a)", since the frach inside creates its own partitions (by default, the "a" partition is the root file system, where we wrote the bootloader). But my record didn’t work, I didn’t bother.

5. Next, in the terminal, enter
$ sudo update-grub
The boot.cfg file is generated, thanks to which our fryha will appear in the list of hornbeam.

That's it, reboot and go to the long-awaited FreeBSD!
If, after all, it doesn’t enter, then perhaps you need to play around with the text in the 40_custom file