dhcpd

After a couple of trial and error tests and lots of caffeine ingested, I finally managed to install FreeBSD 9.1 over my network completely diskless using ISC's DHCP, PXE, tftpd-hpa, and NFS.

Download iso image and copy over all files.

wget ftp://ftp.freebsd.org/pub/FreeBSD/releases/amd64/amd64/ISO-IMAGES/9.0/Fr...
mount -o loop FreeBSD-9.0-RELEASE-amd64-disc1.iso /mnt
mkdir -p /srv/tftp/freebsd/amd64
cp -a /mnt/* /srv/tftp/freebsd/amd64
cp -a /mnt/.cshrc /srv/tftp/freebsd/amd64
cp -a /mnt/.profile /srv/tftp/freebsd/amd64
cp -a /mnt/.rr_moved /srv/tftp/freebsd/amd64

Create the following directories:

mkdir /srv/tftp/freebsd/amd64/jails
mkdir -p /srv/tftp/freebsd/amd64/conf/base/jails
mkdir /srv/tftp/freebsd/amd64/conf/default
chmod -R 777 /srv/tftp/freebsd/amd64/conf
chmod -R 777 /srv/tftp/freebsd/amd64/jails

Edit /srv/tftp/freebsd/amd64/etc/fstab, comment out the entry in the file:

#/dev/iso9660/FREEBSD_INSTALL / cd9660 ro 0 0

Add the following entry to /srv/tftp/freebsd/amd64/etc/rc.conf:

root_rw_mount="NO"

NFS configuration:

/srv/tftp/freebsd/amd64		192.168.1.1/24(ro,sync,no_root_squash,no_subtree_check)

dhcpd configuration (of course, IP may differ depending on your environment):
192.168.1.128 will be the IP that wil be assigned to the new FreeBSD system.
192.168.1.2 is the IP of the NFS server where the installation files are stored in.
The filename path is relative to what path you configured with tftpd-hpa.

host freebsdboot {
  hardware ethernet 08:00:27:2b:f9:f8;
  fixed-address 192.168.1.128;
  filename "freebsd/amd64/boot/pxeboot";
  option root-path "192.168.1.2:/srv/tftp/freebsd/amd64";
}

References:
http://forums.freebsd.org/showthread.php?t=30069
http://lists.freebsd.org/pipermail/freebsd-questions/2012-March/238969.html
http://box.matto.nl/disklessfreebsd.html