Create the root directory which will contain a FreeBSD installation to be NFS mounted:

# export NFSROOTDIR=/b/tftpboot/FreeBSD/install
# mkdir -p ${NFSROOTDIR}

Enable the NFS server by adding this line to /etc/rc.conf:

nfs_server_enable="YES"

Export the diskless root directory via NFS by adding the following to /etc/exports:

/b -ro -alldirs

Start the NFS server:

# service nfsd start

Enable inetd(8) by adding the following line to /etc/rc.conf:

inetd_enable="YES"

Uncomment the following line in /etc/inetd.conf by making sure it does not start with a # symbol:

tftp dgram udp wait root /usr/libexec/tftpd tftpd -l -s /b/tftpboot

Start inetd(8):

# service inetd start

Rebuild the FreeBSD kernel and userland (refer to Section 24.6, “Rebuilding World” for more detailed instructions):

# cd /usr/src
# make buildworld
# make buildkernel

Install FreeBSD into the directory mounted over NFS:

# make installworld DESTDIR=${NFSROOTDIR}
# make installkernel DESTDIR=${NFSROOTDIR}
# make distribution DESTDIR=${NFSROOTDIR}

Test that the TFTP server works and can download the boot loader which will be obtained via PXE:

# tftp localhost
tftp> get FreeBSD/install/boot/pxeboot
Received 264951 bytes in 0.1 seconds

Edit ${NFSROOTDIR}/etc/fstab and create an entry to mount the root file system over NFS:

# Device                                         Mountpoint    FSType   Options  Dump Pass
myhost.example.com:/b/tftpboot/FreeBSD/install       /         nfs      ro        0    0

Replace myhost.example.com with the hostname or IP address of the NFS server. In this example, the root file system is mounted read-only in order to prevent NFS clients from potentially deleting the contents of the root file system.

Set the root password in the PXE environment for client machines which are PXE booting :

# chroot ${NFSROOTDIR}
# passwd

If needed, enable ssh(1) root logins for client machines which are PXE booting by editing ${NFSROOTDIR}/etc/ssh/sshd_config and enabling PermitRootLogin. This option is documented in sshd_config(5).

Perform any other needed customizations of the PXE environment in ${NFSROOTDIR}. These customizations could include things like installing packages or editing the password file with vipw(8).

Use the net/wireshark package or port to debug the network traffic involved during the PXE booting process, which is illustrated in the diagram below.

Figure 31.1. PXE Booting Process with NFS Root Mount

	Client broadcasts a DHCPDISCOVER message.
	The DHCP server responds with the IP address, next-server, filename, and root-path values.
	The client sends a TFTP request to next-server, asking to retrieve filename.
	The TFTP server responds and sends filename to client.
	The client executes filename, which is pxeboot(8), which then loads the kernel. When the kernel executes, the root file system specified by root-path is mounted over NFS.

On the TFTP server, read /var/log/xferlog to ensure that pxeboot is being retrieved from the correct location. To test this example configuration:

# tftp 192.168.0.1
tftp> get FreeBSD/install/boot/pxeboot
Received 264951 bytes in 0.1 seconds

The BUGS sections in tftpd(8) and tftp(1) document some limitations with TFTP.

Make sure that the root file system can be mounted via NFS. To test this example configuration:

# mount -t nfs 192.168.0.1:/b/tftpboot/FreeBSD/install /mnt