PXEBOOT(8)

NAME
pxeboot - Preboot Execution Environment (PXE) bootloader

DESCRIPTION
The pxeboot bootloader is a modified version of the system third-stage bootstrap loader(8) configured to run under Intel's Preboot Execution Environment (PXE) system. PXE is a form of smart boot ROM, built into Intel EtherExpress Pro/100 and 3Com 3c905c Ethernet cards, and Ethernet-equipped Intel motherboards. PXE supports DHCP configuration and provides low-level NIC access services. The pxeboot bootloader retrieves the kernel, modules, and other files either via NFS over UDP. In combination with a NFS-mounted root file system, pxeboot allows for easy, EEPROM-burner free construction of diskless machines.

The pxeboot binary is loaded just like any other boot file, by specifying it in the DHCP server's configuration file. Below is a sample configuration for the ISC DHCP v2 server:

    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;
    default-lease-time 120;
    max-lease-time 120;
    subnet 10.0.0.0 netmask 255.255.255.0 {
           filename "boot/pxeboot";
           range 10.0.0.10 10.0.0.254;
           option root-path "10.0.0.1:/netbootroot";
    }

pxeboot defaults to a conservative 1024 byte NFS data packet. This may be changed by setting the nfs.read_size variable in /boot/loader.conf. Valid values range from 1024 to 4096 bytes.

pxeboot recognizes next-server and option root-path directives as the server and path to NFS mount for file requests, respectively, or the server to make TFTP requests to. Note that pxeboot expects to fetch /boot/dloader.rc from the specified server before loading any other files.

pxeboot uses /boot/kernel.BOOTP and /boot/loader-bootp.conf instead of /boot/kernel and /boot/loader.conf. Note that the TFTP version pxeboot_tftp(8) uses the standard boot loader files. The NFS version uses different files to allow BOOTP boots via NFS to be overloaded onto the same directory structure as a normal boot, though many other changes would have to be made to actually make that work. However, this is more for historical reasons. Current day PXE boot code can handle complex root-path specifications allowing the root image to be contained in a sub-directory of the NFS export.

In all other respects, pxeboot acts just like loader(8).

As PXE is still in its infancy, some firmware versions may not work properly. The pxeboot bootloader has been extensively tested on version 0.99 of Intel firmware; pre-release versions of the newer 2.0 firmware are known to have problems. Check with the device's manufacturer for their latest stable release.

For further information on Intel's PXE specifications and Wired for Management (WfM) systems, see http://developer.intel.com/ial/wfm/.

FILES
/boot/kernel.BOOTP
    Default kernel for pxeboot.
/boot/defaults/loader-bootp.conf
    pxeboot configuration file -- do not change this file.
/boot/loader-bootp.conf
    pxeboot configuration file.

SEE ALSO
dhcpd(8) (net/isc-dhcp42-server), diskless(8), loader(8), nfsd(8), pxeboot_tftp(8), tftpd(8)

HISTORY
The pxeboot bootloader first appeared in FreeBSD 4.1.

AUTHORS
-nosplit The pxeboot bootloader was written by John Baldwin <jhb@FreeBSD.org> and Paul Saab <ps@FreeBSD.org>. This manual page was written by Doug White <dwhite@FreeBSD.org>.