Configuring a Diskless FreeBSD Client and Boot Server
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Prepared by: Todd Pfaff <todd@flex.eng.mcmaster.ca>
Martin Renters <martin@innovus.com>
Last update: Jan. 31, 1994
Martin Renters developed the diskless boot code for FreeBSD and has tested
Todd Pfaff has used a SunOS 4.1.2 Sun 4 server to support a diskless FreeBSD
client. The following procedure applies to that environment so your mileage
The following Ethernet cards have been tested with netboot:
Currently, diskless clients must be on the same subnet as the NFS server.
Code has been added to the diskless_cfg program to allow for booting clients
across a gateway, but the kernel code (in /usr/src/sys/nfs/nfs_vfsops.c) to
add a default route at boot time is not yet working.
<server> - host name of root/swap NFS server
<client> - host name of diskless FreeBSD client
<tftp_root> - path to TFTP root directory on TFTP server
(usually /tftpboot on SunOS 4.1.x)
<client_root> - path to client root filesystem on NFS server
(eg. /export/root/<client>)
<client_swap> - path to client swap file on NFS server
(eg. /export/swap/<client>)
<client_usr> - path to client usr filesystem on NFS server
<swap_size> - size of swap file in 512 byte blocks
1) Configure a bootp server.
CMU bootp-2.1 has been verified to do the job on a Sun 4/SunOS 4.1.2.
Create a bootptab entry for the diskless client. For example:
2) Configure a tftp server.
I already had this set up for diskless SunOS clients so I didn't have to do
You will later place the client kernel and diskless configuration file in
3) Build a diskless kernel.
You must have a standalone FreeBSD system running to create a kernel
Make sure you are running a current config. If not, rebuild and install
/usr/src/usr.sbin/config.
Create a kernel configuration with:
config "386bsd" swap on nfs size <swap_size>
and config and make this kernel.
Install the kernel in <tftp_root> and <server>:<client_root>.
Here's a minimal diskless kernel config file:
config "386bsd" swap on nfs size 50000
controller fd0 at isa? port "IO_FD1" bio irq 6 drq 2 vector fdintr
device pc0 at isa? port "IO_KBD" tty irq 1 vector pcrint
device npx0 at isa? port "IO_NPX" irq 13 vector npxintr
device sio0 at isa? port "IO_COM1" tty irq 4 vector siointr
device sio1 at isa? port "IO_COM2" tty irq 3 vector siointr
device lpt0 at isa? port "IO_LPT1" tty irq 7 vector lptintr
device ed0 at isa? port 0x300 net irq 5 iomem 0xd0000 vector edintr
4) Create a client root filesystem and swap file on the NFS server.
Make a new directory which will be the client's root filesystem.
This should include /bin, /dev, /etc, /sbin, /tmp, /var, a mountpoint
for /usr, and the client kernel (386bsd or whatever is given in the
bf field of the bootptab entry).
For example, you can copy the root filesystem from a standalone FreeBSD
<server># mkdir <client_root>
<server># mount freebsdhost:/ /mnt
<server># find * -print | cpio -pm <client_root>
<server># touch <client_swap>
<server># mkfile -n <swap_size>b <client_swap>
Export this root and swap to <client>.
A few things to modify in the client root directory:
Make sure all the devices you need are there.
If not you will have to mount this directory on a running
FreeBSD system and use MAKEDEV.
[This one bit me because I used tar to copy an root filesystem and
none of the device files were copied. Use cpio if you want to copy
a root filesystem and preserve device files. -TP]
Delete this. You probably don't want your diskless client to be an
You need at least the following entries:
<server>:<client_root> / nfs rw 0 0
<server>:<client_usr> /usr nfs rw 0 0
Set interface config and default route.
and remove the final 'mount -a -t nfs' at the end of rc.
5) Create a diskless configuration file.
The program /sbin/diskless_cfg is used to create a configuration file
which is loaded via tftp from the server by the netboot program.
This program must be run on the NFS server from which root and swap
will be mounted because it stores the server hostname and file handles
of the root path and swap file in a file.
Build /usr/src/usr.sbin/diskless_cfg on your NFS server.
The supplied Makefile is meant to build diskless_cfg under a FreeBSD
source tree, but you can compile diskless_cfg manually with:
cc -DNFS diskless_cfg.c -o diskless_cfg
Run the program as follows:
diskless_cfg -rootfs <client_root> -swap <client_swap> -hostname <client>
and this will create a file cfg.X.X.X.X where X.X.X.X is the decimal IP
Copy cfg.X.X.X.X to <tftp_root>.
6) Compile the netboot.com program.
cd /sys/i386/netboot; make
At the top of wd80x3.c in /sys/i386/netboot/wd80x3.c is a line:
#define WE_DEFAULT_MEM 0xD0000
which defines the Ethernet adapter RAM buffer address. Make sure you edit
this to reflect the address given in your diskless kernel config file:
device ed0 at isa? port 0x300 net irq 5 iomem 0xd0000 vector edintr
Copy netboot.com to a DOS disk or put netboot.rom into a boot PROM for
Run netboot.com from DOS to initiate the diskless client boot.
If your bootp server is not responding you can set the IP addresses of the
client and server manually and continue. Press escape during the boot to
to the netboot monitor. Type help in the netboot monitor for a list of
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