NAME
pxeboot
—
Preboot Execution Environment (PXE)
bootloader
DESCRIPTION
Thepxeboot
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 and
nextboot-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
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>.