pxeboot(8) - OpenBSD manual pages

NAME

pxeboot — amd64-specific second-stage PXE bootstrap

pxeboot is a modified version of the amd64 second-stage bootstrap program, boot(8), configured to run under Intel's Preboot Execution Environment (PXE). PXE is a form of smart boot ROM, built into many Ethernet cards from Intel, 3Com, and other manufacturers.

The computer's PXE boot ROM contacts a DHCP server by broadcasting a request on the network. It gets an IP address from the DHCP server, then it is told the name of the boot program to download — in this case, the boot program is pxeboot. The ROM downloads the boot program using TFTP, then executes it.

The pxeboot boot program will look for an /etc/boot.conf configuration file on the TFTP server. If it finds one, it processes the commands within it. boot.conf processing can be skipped by holding down either Control key as pxeboot starts.

pxeboot then sits in a loop, processing commands given by the user. It accepts all the commands accepted by boot(8).

If no commands are given for a short time, pxeboot will then attempt to load the OpenBSD kernel bsd via TFTP. It may be told to boot an alternative kernel, either by commands in the boot.conf file, or by commands typed by the user at the boot> prompt. pxeboot can be used for diskless(8) setups or to load the bsd.rd install kernel for network installs.

To prepare a server to support network booting, the dhcpd(8) and tftpd(8) services should be enabled and configured.

pxeboot and the kernel should be copied into the TFTP server's root directory (typically /tftpboot). A boot.conf file may be created if required (e.g. /tftpboot/etc/boot.conf).

A sample configuration file for dhcpd(8) might be as follows:

option domain-name "example.com";
option routers 10.0.0.1;
option subnet-mask 255.255.255.0;
option broadcast-address 10.0.0.255;
option domain-name-servers 10.0.0.1;
server-name "DHCPserver";
server-identifier 10.0.0.1;
next-server 10.0.0.1;

default-lease-time 120;
max-lease-time 120;

subnet 10.0.0.0 netmask 255.255.255.0 {
    filename "pxeboot";
    range 10.0.0.10 10.0.0.254;
}

Since amd64 systems boot up as i386 systems, their PXE ROMs typically set the PXE client system architecture to be the same as for i386. This means that the DHCP option vendor-class-identifier cannot, therefore, be used to distinguish between i386 and amd64 systems.

Instead, the client machine identifier (UUID) or hardware Ethernet address (MAC) should be used. See dhcpd(8) and dhcpd.conf(5) for more information.