grub legacy and grub2 config to install netbsd

mkdir /boot/netbsd
cd /boot/netbsd
wget ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-5.1/i386/binary/kernel/netbsd-INSTALL_FLOPPY.gz
gunzip netbsd-INSTALL_FLOPPY.gz

If you only have a single Linux partition, and it is the first partition of your hard drive

# Grub Legacy: stuff to add to grub legacy's /boot/grub/menu.st
title NetBSD Installer
root (hd0,0)
kernel --type=netbsd  /boot/netbsd/netbsd-INSTALL_FLOPPY

# GRUB2: Stuff to add to /etc/grub.d/40_custom
menuentry "NetBSD Installer" {
set root=(hd0,msdos1)
multiboot /boot/netbsd/netbsd-INSTALL_FLOPPY
}