1. loading a boot program

DEC Alpha systems use BOOTP to determine the client's IP address and then use TFTP load a secondary bootstrap program from the server and filename specified in the BOOTP reply. DEC Alpha systems can also use MOP to load a program to run the system.

Sun systems use RARP to determine the client's IP address, transform that address to a hexadecimal string to form the filename of the secondary boot program, and then use TFTP to download the boot program from the server that sent the RARP reply.

HP 300-series systems use the HP RMP to download a boot program.

Typical personal computers may load a network boot program either from diskette or from a PROM on a Network Interface Card (NIC). Some BIOSes support booting from a network interface.

2. loading a kernel

1. gets the client IP address using RARP.
2. gets the client name and server IP address by broadcasting an RPC / BOOTPARAMS / WHOAMI request with the client IP address.
3. gets the server path for this client's root using an RPC / BOOTPARAMS / GETFILE request with the client name.
4. gets the root file handle by calling mountd(8) with the server path for the client root file system.
5. gets the kernel file handle by calling NFS lookup() on the root file handle.
6. loads the kernel using NFS read calls on the kernel file handle.
7. transfers control to the kernel entry point.

A BOOTP and/or DHCP secondary bootstrap program will do the following:

1. query for the client's bootstrap parameters. The response must include the client's IP address, and a TFTP server to load the NetBSD kernel from.
2. loads the NetBSD kernel from the TFTP server.
3. transfers control to the kernel entry point.

3. NFS mounting the root file system

In general, the GENERIC kernel config(1) file for any particular architecture will specify compile-time options to use the same protocol used by the secondary boot program for that architecture. A NetBSD kernel can be compiled to use any of BOOTP, DHCP, or Sun RPC BOOTPARAMS; see options(4).

The procedure typically used by the kernel is as follows:

1. The kernel finds a boot server using the same procedures as described above to determine the client's IP address, an NFS server, etc.
2. The kernel gets the NFS file handle for root using the same procedure as described above.
3. The kernel calls the NFS getattr() function to get the last-modified time of the root directory, and uses it to check the system clock.

RARP

8:0:20:7:c5:c7          myclient

This will be used by rarpd(8) to reply to queries from the clients. There must be one entry per client system.

A client system's Ethernet MAC address is often printed on the system case, or on a chip on its motherboard, or on the NIC. If not, “sniffing” the network with tcpdump(8) when the client is powered-on should reveal its Ethernet MAC address.

Each client system that uses RARP must have its own, unique IP address assigned to it. Assign an IP address for myclient in your /etc/hosts file, or in the master file for your DNS zone. For /etc/hosts the entry should look like:

192.197.96.12           myclient

DHCP/BOOTP

DHCP can provide a wide range of information to a requesting client; the key data for bootstrapping a diskless client are:

1. an IP address
2. a subnet mask
3. a TFTP server address for loading the secondary bootstrap and the NetBSD kernel
4. a filename of the secondary bootstrap
5. an NFS server address for the client's file system
6. the client's root file system path, to be NFS mounted.

An example for /etc/dhcpd.conf

host myclient { 
	hardware ethernet 8:0:20:7:c5:c7; 
	fixed-address myclient;		# client's assigned IP address 
	filename "myclient.netboot";	# secondary bootstrap 
	next-server myserver;		# TFTP server for secondary bootstrap 
	option swap-server myserver;	# NFS server for root filesystem 
	option root-path "/export/myclient/root"; 
}

That host declaration goes inside a subnet declaration, which gives parameters for all hosts on the subnet that will be using DHCP, such as the “routers” (the default route), “subnet-mask”, “broadcast-address”, “domain-name-servers”, etc. See dhcpd.conf(5) for details. In that example, myclient has an assigned IP address.

The DHCP parameters required for network bootstrapping a system will vary from platform to platform, as dictated by each system's firmware. In particular, because the DHCP is extensible, some hardware vendors have specified DHCP options to return information to requesting clients that are specific to that platform. Please see your platform's boot(8) for details.

TFTP

If booting a SPARC system, install a copy of the appropriate diskless secondary boot loader (such as /usr/mdec/boot or ofwboot.net) in the /tftpboot directory. Make a link such that the boot program is accessible by a filename composed of the client's IP address in hexadecimal, a dot, and the architecture name (all upper case). For example:

# cd /tftpboot 
# ln -s boot C0C5600C.SUN4

For a Sun-3 or UltraSPARC system, the filename would be just C0C5600C (these systems' firmware does not append the architecture name). The name used is architecture dependent, it simply has to match what the booting client's system firmware wishes to it to be.

If the client's system firmware fails to fetch the expected file, tcpdump(8) can be used to discover which filename the client is being requested. Also, examination of tftpd(8) log entries (typically in /var/log/messages) should show whether the server is hearing the client system, and what filename the client is asking for.

HP RMP

08:00:09:01:23:E6	SYS_UBOOT	# myclient

The secondary bootstrap program for an HP 300-series system SYS_UBOOT (which may be called uboot.lif before installation) must be installed in the directory /usr/mdec/rbootd.

See the rbootd(8) manual page for more information.

Sun RPC BOOTPARAMS

myclient  root=myserver:/export/myclient/root \ 
          swap=myserver:/export/myclient/root/swap \ 
          dump=myserver:/export/myclient/root/swap

and ensure that rpc.bootparamd(8) and rpcbind(8) are running. Both myclient and myserver must have IP addresses in the DNS or /etc/hosts.

Diskless Client File Systems

# cd /export/myclient/root 
# dd if=/dev/zero of=swap bs=16k count=1024

This creates a 16 megabyte swap file.

Populate myclient's root file system on the NFS server. How this is done depends on the client architecture and the version of the NetBSD distribution. It can be as simple as copying and modifying the server's root file system, or unpack a complete NetBSD binary distribution for the appropriate platform.

If the NFS server is going to support multiple different architectures (e.g. Alpha, PowerPC, SPARC, MIPS), then it is important to think carefully about how to lay out the NFS server's exported file systems, to share what can be shared (e.g. text files, configuration files, user home directories), and separate that which is distinct to each architecture (e.g. binary executables, libraries).

NFS

/usr -ro myclient 
# for SunOS: 
# /export/myclient -rw=myclient,root=myclient 
# for NetBSD: 
/export/myclient -maproot=root -alldirs myclient

If the server and client are of the same architecture, then the client can share the server's /usr file system (as is done above). If not, you must build a properly fleshed out /usr partition for the client in some other part of the server's file system, to serve to the client.

If your server is a SPARC, and your client a Sun-3, you might create and fill /export/usr.sun3 and then use the following /etc/exports lines:

/export/usr.sun3 -ro myclient 
/export/myclient -rw=myclient,root=myclient

Of course, in either case you will have to have an NFS server running on the server side.