Multiboot NetBSD and Debian GNU/Linux with GRUB2

Debian GNU/Linux 8 Jessie Beta2 and NetBSD 7_BETA on the same pc.
 
Linux is on /dev/sda1
NetBSD partition is on /dev/sda4
Grub is installed on master boot record (/dev/sda).

Edit /etc/grub.d/40_custom and add the following lines:

menuentry "NetBSD 7 on sda4" {
        insmod ufs2
        insmod bsd
        set root=(hd0,4)
        chainloader (hd0,4)+1
}

Don't forget to do 'update-grub' before rebooting.