.\" Copyright (c) 1999 Doug White
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.Dd May 25, 2017
.Dt PXEBOOT 5
.Os
.Sh NAME
.Nm pxeboot
.Nd Preboot Execution Environment (PXE) bootloader
.Sh DESCRIPTION
The
.Nm
bootloader is a modified version of the system third-stage bootstrap
.Xr loader 5
configured to run under Intel's Preboot Execution Environment (PXE) system.
PXE is a form of smart boot ROM, built into Ethernet cards, and
Ethernet-equipped motherboards.
PXE supports DHCP configuration and provides low-level NIC access services.
The
.Nm
bootloader retrieves the kernel, modules,
and other files either via NFS over UDP or by TFTP,
selectable through DHCP options.
.Pp
The
.Nm
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:
.Bd -literal -offset indent
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 "pxeboot";
       range 10.0.0.10 10.0.0.254;
}

.Ed
.Pp
.Nm
recognizes
.Va next-server
and
.Va 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
.Nm
expects to fetch
.Pa /boot/loader.rc
from the specified server before loading any other files.
.Pp
.Nm
defaults to a conservative 1024 byte NFS data packet size.
This may be changed by setting the
.Va nfs.read_size
variable in
.Pa /boot/loader.conf .
Valid values range from 1024 to 4096 bytes.
.Pp
.Nm
chooses NFS or TFTP based on the value of
.Va root-path
variable provided by the DHCP server.
.Nm
defaults to use NFS if the
.Va root-path
variable is in the
.Qq Pa ip-address Ns :/ Ns Pa path
form, otherwise TFTP is used.
.Pp
TFTP block size can be controlled by setting the
.Va tftp.blksize
variable in
.Pa /boot/loader.conf .
Valid values range from 8 to 9008 bytes.
.Pp
In all other respects,
.Nm
acts just like
.Xr loader 5 .
.Pp
For further information on Intel's PXE specifications and Wired for
Management (WfM) systems, see
.Li http://www.intel.com/design/archives/wfm/ .
.Sh SEE ALSO
.Xr loader 5