txt/pxelinux.txt - pub/scm/boot/syslinux/syslinux - Git at Google

 = pxelinux(1) =
 :doctype: manpage
 :revdate: 2013-06-12
 :author: H. Peter Anvin
 :author-email: hpa@zytor.com
 :editor1: Gene Cumm
 :editor1-email: gene.cumm@gmail.com
 :editor1-revlast: 2013-06-12


 == NAME ==
 pxelinux - The Syslinux derivative PXELINUX for PXE network booting


 == SYNOPSIS ==
 [verse]
 pxelinux.0


 == DESCRIPTION ==
 *PXELINUX* is a Syslinux derivative, for booting Linux off a network
 server, using a network ROM conforming to the Intel PXE (Pre-Execution
 Environment) specification.  *PXELINUX* is _*not*_ a program that is
 intended to be flashed or burned into a PROM on the network card; if
 you want that, check out Etherboot (http://www.etherboot.org/).
 Etherboot 5.4 or later can also be used to create a PXE-compliant boot
 PROM for many network cards.
 //FIXME: Needs gPXE/iPXE note

 PXELINUX generally requires that full file pathnames are 127 characters or shorter in length.
 //FIXME: why?  many tftpds limiting to 127+null?  outdated?


 == CURRENT DIRECTORY ==
 The initial current working directory is either as supplied by DHCP
 option 210 (pxelinux.pathprefix), the hardcoded path-prefix or the
 parent directory of the PXELINUX file, as indicated by DHCP fields
 'sname' and 'file' (sname="192.168.2.3" and file="boot/pxelinux.0"
 results in "tftp://192.168.2.3/boot/", "192.168.2.3::boot/" in older
 PXELINUX format) with precedence specified under *OPTIONS*.

 All unqualified filenames are relative to the current directory.


 == CONFIGURATION ==
 See *syslinux.cfg*(5) for the format of the contents.

 Because more than one system may be booted from the same server, the
 configuration file name depends on the IP address of the booting
 machine.  After attempting the file as specified in the DHCP or
 hardcoded options, PXELINUX will probe the following paths, prefixed
 with "pxelinux.cfg/", under the initial current working directory:

 - The client UUID if provided by the PXE stack (note, some BIOSes don't
 have a valid UUID, and you might end up with something like all 1's.)
 This is in the standard UUID format using lower case hexadecimal digits,
 e.g. b8945908-d6a6-41a9-611d-74a6ab80b83d.

 - The hardware type (using its ARP type code) and address, all in lower
 case hexadecimal with dash separators; for example, for an Ethernet (ARP
 type 1) with address 88:99:AA:BB:CC:DD it would search for the filename
 01-88-99-aa-bb-cc-dd.

 - The client's IPv4 address in upper-case hexidecimal (ie 192.168.2.91
 -> C0A8025B; you can use the included progam "gethostip" to compute the
 hexadecimal IP address for any host.) followed by removing characters,
 one at a time, from the end.

 - "default"

 Starting in release 3.20, if PXELINUX can not find a configuration file,
 it will reboot after the timeout interval has expired.  This keeps a
 machine from getting stuck indefinitely due to a boot server failure.


 == OPTIONS ==
 *PXELINUX* (starting with version 1.62) supports the following
 nonstandard DHCP options, which depending on your DHCP server you may be
 able to use to customize the specific behaviour of *PXELINUX*.  See RFC
 5071 for some additional information about these options. Options for
 *PXELINUX* can be specified by DHCP options or hardcoded into the
 binary.

 === Option Priority ===
 Hardcoded after-options are applied after DHCP options (and overrride)
 while hardcoded before-options are applied prior to DHCP options and
 default behavior takes the lowest priority.

 === DHCP options ===
 *Option 208* (pxelinux.magic)::
 Earlier versions of *PXELINUX* required this to be set to F1:00:74:7E
 (241.0.116.126) for *PXELINUX* to recognize any special DHCP options
 whatsoever.  As of *PXELINUX* 3.55, this option is deprecated and is no
 longer required.

 *Option 209* (pxelinux.configfile)::
 Specifies the initial *PXELINUX* configuration file name which may be
 qualified or unqualified.

 *Option 210* (pxelinux.pathprefix)::
 Specifies the *PXELINUX* common path prefix, instead of deriving it from
 the boot file name.  This almost certainly needs to end in whatever
 character the TFTP server OS uses as a pathname separator, e.g. slash
 (/) for Unix.

 *Option 211* (pxelinux.reboottime)::
 Specifies, in seconds, the time to wait before reboot in the event of
 TFTP failure.  0 means wait "forever" (in reality, it waits
 approximately 136 years.)

 === Hardcoded options ===
 Since version 3.83, the program "pxelinux-options" can be used to
 hard-code DHCP options into the pxelinux.0 image file; this is
 sometimes useful when the DHCP server is under different
 administrative control.  Hardcoded options

       6 => 'domain-name-servers',
      15 => 'domain-name',
      54 => 'next-server',
     209 => 'config-file',
     210 => 'path-prefix',
     211 => 'reboottime'


 == HTTP/FTP ==
 Since version 5.10, a special PXELINUX binary, lpxelinux.0, natively
 supports HTTP and FTP transfers, greatly increasing load speed and
 allowing for standard HTTP scripts to present PXELINUX's configuration
 file.  To use http or ftp, use standard URL syntax as filename; use the
 DHCP options below to transmit a suitable URL prefix to the client, or
 use the "pxelinux-options" tool provided in the utils directory to
 program it directly into the lpxelinux.0 file.


 == FILENAME SYNTAX ==
 //FIXME
 PXELINUX supports the following special pathname conventions:

 *::filename*::
 Suppresses the common filename prefix, i.e. passes the string "filename"
 unmodified to the server.

 *IP address::filename* (e.g. 192.168.2.3::filename)::
 Suppresses the common filename prefix, *and* sends a request to an alternate TFTP server.  Instead of an IP address, a DNS name can be used.  It will be assumed to be fully qualified if it contains dots; otherwise the local domain as reported by the DHCP server (option 15) will be added.

 :: was chosen because it is unlikely to conflict with operating system
 usage.  However, if you happen to have an environment for which the
 special treatment of :: is a problem, please contact the Syslinux
 mailing list.

 Since version 4.00, PXELINUX also supports standard URL syntax.


 == KEEPPXE ==
 Normally, PXELINUX will unload the PXE and UNDI stacks before invoking
 the kernel.  In special circumstances (for example, when using MEMDISK
 to boot an operating system with an UNDI network driver) it might be
 desirable to keep the PXE stack in memory.  If the option "keeppxe"
 is given on the kernel command line, PXELINUX will keep the PXE and
 UNDI stacks in memory.  (If you don't know what this means, you
 probably don't need it.)


 == EXAMPLES ==

 === Configuration filename ===
 For DHCP siaddr 192.168.2.3, file 'mybootdir/pxelinux.0', client UUID
 b8945908-d6a6-41a9-611d-74a6ab80b83d, Ethernet MAC address
 88:99:AA:BB:CC:DD and IPv4 address 192.168.2.91, the following files in
 this order will be attempted (after config-file options):

 	mybootdir/pxelinux.cfg/b8945908-d6a6-41a9-611d-74a6ab80b83d
 	mybootdir/pxelinux.cfg/01-88-99-aa-bb-cc-dd
 	mybootdir/pxelinux.cfg/C0A8025B
 	mybootdir/pxelinux.cfg/C0A8025
 	mybootdir/pxelinux.cfg/C0A802
 	mybootdir/pxelinux.cfg/C0A80
 	mybootdir/pxelinux.cfg/C0A8
 	mybootdir/pxelinux.cfg/C0A
 	mybootdir/pxelinux.cfg/C0
 	mybootdir/pxelinux.cfg/C
 	mybootdir/pxelinux.cfg/default


 === TFTP servers ===
 For best results, use a TFTP server which supports the "tsize" TFTP
 option (RFC 1784/RFC 2349).  The "tftp-hpa" TFTP server, which support
 options, is available at:

 	http://www.kernel.org/pub/software/network/tftp/
 	ftp://www.kernel.org/pub/software/network/tftp/

 and on any kernel.org mirror (see http://www.kernel.org/mirrors/).

 Another TFTP server which supports this is atftp by Jean-Pierre
 Lefebvre:

 	ftp://ftp.mamalinux.com/pub/atftp/

 If your boot server is running Windows (and you can't fix that), try
 tftpd32 by Philippe Jounin (you need version 2.11 or later; previous
 versions had a bug which made it incompatible with PXELINUX):

 	http://tftpd32.jounin.net/


 === DHCP config: Simple ===
 The PXE protocol uses a very complex set of extensions to DHCP or
 BOOTP.  However, most PXE implementations -- this includes all Intel
 ones version 0.99n and later -- seem to be able to boot in a
 "conventional" DHCP/TFTP configuration.  Assuming you don't have to
 support any very old or otherwise severely broken clients, this is
 probably the best configuration unless you already have a PXE boot
 server on your network.

 A sample DHCP setup, using the "conventional TFTP" configuration,
 would look something like the following, using ISC dhcp 2.0 dhcpd.conf
 syntax:

 -----
 allow booting;
 allow bootp;

 # Standard configuration directives...

 option domain-name "<domain name>";
 option subnet-mask <subnet mask>;
 option broadcast-address <broadcast address>;
 option domain-name-servers <dns servers>;
 option routers <default router>;

 # Group the PXE bootable hosts together
 group {
 	# PXE-specific configuration directives...
 	next-server <TFTP server address>;
 	filename "/tftpboot/pxelinux.0";

 	# You need an entry like this for every host
 	# unless you're using dynamic addresses
 	host <hostname> {
 		hardware ethernet <ethernet address>;
 		fixed-address <hostname>;
 	}
 }
 -----

 Note that if your particular TFTP daemon runs under chroot (tftp-hpa
 will do this if you specify the -s (secure) option; this is highly
 recommended), you almost certainly should not include the /tftpboot
 prefix in the filename statement.


 === DHCP Config: PXE-1 ===
 If the simple config does not work for your environment, you probably
 should set up a "PXE boot server" on port 4011 of your TFTP server; a
 free PXE boot server is available at:

 http://www.kano.org.uk/projects/pxe/

 With such a boot server defined, your DHCP configuration should look
 the same except for an "option dhcp-class-identifier" ("option
 vendor-class-identifier" if you are using DHCP 3.0):

 ----
 allow booting;
 allow bootp;

 # Standard configuration directives...

 option domain-name "<domain name>";
 option subnet-mask <subnet mask>;
 option broadcast-address <broadcast address>;
 option domain-name-servers <dns servers>;
 option routers <default router>;

 # Group the PXE bootable hosts together
 group {
 	# PXE-specific configuration directives...
 	option dhcp-class-identifier "PXEClient";
 	next-server <pxe boot server address>;

 	# You need an entry like this for every host
 	# unless you're using dynamic addresses
 	host <hostname> {
 		hardware ethernet <ethernet address>;
 		fixed-address <hostname>;
 	}
 }
 ----

 Here, the boot file name is obtained from the PXE server.


 === DHCP Config: Encapsulated ===
 If the "conventional TFTP" configuration doesn't work on your clients,
 and setting up a PXE boot server is not an option, you can attempt the
 following configuration.  It has been known to boot some
 configurations correctly; however, there are no guarantees:
 ----
 allow booting;
 allow bootp;

 # Standard configuration directives...

 option domain-name "<domain name>";
 option subnet-mask <subnet mask>;
 option broadcast-address <broadcast address>;
 option domain-name-servers <dns servers>;
 option routers <default router>;

 # Group the PXE bootable hosts together
 group {
 	# PXE-specific configuration directives...
 	option dhcp-class-identifier "PXEClient";
 	option vendor-encapsulated-options 09:0f:80:00:0c:4e:65:74:77:6f:72:6b:20:62:6f:6f:74:0a:07:00:50:72:6f:6d:70:74:06:01:02:08:03:80:00:00:47:04:80:00:00:00:ff;
 	next-server <TFTP server>;
 	filename "/tftpboot/pxelinux.0";

 	# You need an entry like this for every host
 	# unless you're using dynamic addresses
 	host <hostname> {
 		hardware ethernet <ethernet address>;
 		fixed-address <hostname>;
 	}
 }
 ----
 Note that this *will not* boot some clients that *will* boot with the
 "conventional TFTP" configuration; Intel Boot Client 3.0 and later are
 known to fall into this category.


 === DHCP Config: ISC dhcpd options ===
 ISC dhcp 3.0 supports a rather nice syntax for specifying custom
 options; you can use the following syntax in dhcpd.conf if you are
 running this version of dhcpd:
 ----
 option space pxelinux;
 option pxelinux.magic      code 208 = string;
 option pxelinux.configfile code 209 = text;
 option pxelinux.pathprefix code 210 = text;
 option pxelinux.reboottime code 211 = unsigned integer 32;
 ----
     NOTE: In earlier versions of PXELINUX, this would only work as a
     "site-option-space".  Since PXELINUX 2.07, this will work both as a
     "site-option-space" (unencapsulated) and as a "vendor-option-space"
     (type 43 encapsulated.)  This may avoid messing with the
     dhcp-parameter-request-list, as detailed below.

 Then, inside your PXELINUX-booting group or class (whereever you have
 the PXELINUX-related options, such as the filename option), you can
 add, for example:
 ----
 # Always include the following lines for all PXELINUX clients
 site-option-space "pxelinux";
 option pxelinux.magic f1:00:74:7e;
 if exists dhcp-parameter-request-list {
 	# Always send the PXELINUX options (specified in hexadecimal)
 	option dhcp-parameter-request-list = concat(option dhcp-parameter-request-list,d0,d1,d2,d3);
 }
 # These lines should be customized to your setup
 option pxelinux.configfile "configs/common";
 option pxelinux.pathprefix "/tftpboot/pxelinux/files/";
 option pxelinux.reboottime 30;
 filename "/tftpboot/pxelinux/pxelinux.bin";
 ----
 Note that the configfile is relative to the pathprefix: this will look
 for a config file called /tftpboot/pxelinux/files/configs/common on
 the TFTP server.

 The "option dhcp-parameter-request-list" statement forces the DHCP
 server to send the PXELINUX-specific options, even though they are not
 explicitly requested.  Since the DHCP request is done before PXELINUX
 is loaded, the PXE client won't know to request them.

 Using ISC dhcp 3.0 you can create a lot of these strings on the fly.
 For example, to use the hexadecimal form of the hardware address as
 the configuration file name, you could do something like:
 ----
 site-option-space "pxelinux";
 option pxelinux.magic f1:00:74:7e;
 if exists dhcp-parameter-request-list {
 	# Always send the PXELINUX options (specified in hexadecimal)
 	option dhcp-parameter-request-list = concat(option dhcp-parameter-request-list,d0,d1,d2,d3);
 }
 option pxelinux.configfile =
 	concat("pxelinux.cfg/", binary-to-ascii(16, 8, ":", hardware));
 filename "/tftpboot/pxelinux.bin";
 ----
 If you used this from a client whose Ethernet address was
 58:FA:84:CF:55:0E, this would look for a configuration file named
 "/tftpboot/pxelinux.cfg/1:58:fa:84:cf:55:e".


 == KNOWN ISSUES ==
 The following problems are known with PXELINUX, so far:

 - The error recovery routine doesn't work quite right.  For right now,
   it just does a hard reset - seems good enough.
 - We should probably call the UDP receive function in the keyboard
   entry loop, so that we answer ARP requests.
 - Boot sectors/disk images are not supported yet.

 If you have additional problems, please contact the Syslinux mailing
 list (see syslinux.txt for the address.)

 === Broken PXE stacks ===
 Lots of PXE stacks, especially old ones, have various problems of
 varying degrees of severity.  Please see:

 	http://syslinux.zytor.com/hardware.php

 ... for a list of currently known hardware problems, with workarounds
 if known.

 There are a number of extremely broken PXE stacks in the field.  The
 gPXE project (formerly known as Etherboot) provides an open-source PXE
 stack that works with a number of cards, and which can be loaded from
 a CD-ROM, USB key, or floppy if desired.

 Information on gPXE is available from:

 	http://www.etherboot.org/

 ... and ready-to-use ROM or disk images from:

 	http://www.rom-o-matic.net/

 Some cards, like may systems with the SiS 900, has a PXE stack which
 works just barely well enough to load a single file, but doesn't
 handle the more advanced items required by PXELINUX.  If so, it is
 possible to use the built-in PXE stack to load gPXE, which can then
 load PXELINUX.  See:

 	http://www.etherboot.org/wiki/pxechaining


 == NOTES ==
 === MTFTP ===
 PXELINUX does not support MTFTP, and there are no plans of doing so, as
 MTFTP is inherently broken for files more than 65535 packets (about 92
 MB) in size.  It is of course possible to use MTFTP for the initial
 boot, if you have such a setup.  MTFTP server setup is beyond the scope
 of this document.

 === Error Recovery ===
 If the boot fails, PXELINUX (unlike SYSLINUX) will not wait forever;
 rather, if it has not received any input for approximately five
 minutes after displaying an error message, it will reset the machine.
 This allows an unattended machine to recover in case it had bad enough
 luck of trying to boot at the same time the TFTP server goes down.


 == SEE ALSO ==
 *syslinux.cfg*(5), *syslinux-cli*(1), *lilo*(8), *keytab-lilo.pl*(8),
 *fdisk*(8), *mkfs*(8), *superformat*(1).


 == AUTHOR ==
 This AsciiDoc derived document is a modified version of the original
 *SYSLINUX* documentation by {author} <{author-email}>.  The conversion
 to an AsciiDoc was made by {editor1} <{editor1-email}>
	= pxelinux(1) =
	:doctype: manpage
	:revdate: 2013-06-12
	:author: H. Peter Anvin
	:author-email: hpa@zytor.com
	:editor1: Gene Cumm
	:editor1-email: gene.cumm@gmail.com
	:editor1-revlast: 2013-06-12


	== NAME ==
	pxelinux - The Syslinux derivative PXELINUX for PXE network booting


	== SYNOPSIS ==
	[verse]
	pxelinux.0


	== DESCRIPTION ==
	PXELINUX is a Syslinux derivative, for booting Linux off a network
	server, using a network ROM conforming to the Intel PXE (Pre-Execution
	Environment) specification. PXELINUX is _not_ a program that is
	intended to be flashed or burned into a PROM on the network card; if
	you want that, check out Etherboot (http://www.etherboot.org/).
	Etherboot 5.4 or later can also be used to create a PXE-compliant boot
	PROM for many network cards.
	//FIXME: Needs gPXE/iPXE note

	PXELINUX generally requires that full file pathnames are 127 characters or shorter in length.
	//FIXME: why? many tftpds limiting to 127+null? outdated?


	== CURRENT DIRECTORY ==
	The initial current working directory is either as supplied by DHCP
	option 210 (pxelinux.pathprefix), the hardcoded path-prefix or the
	parent directory of the PXELINUX file, as indicated by DHCP fields
	'sname' and 'file' (sname="192.168.2.3" and file="boot/pxelinux.0"
	results in "tftp://192.168.2.3/boot/", "192.168.2.3::boot/" in older
	PXELINUX format) with precedence specified under OPTIONS.

	All unqualified filenames are relative to the current directory.


	== CONFIGURATION ==
	See syslinux.cfg(5) for the format of the contents.

	Because more than one system may be booted from the same server, the
	configuration file name depends on the IP address of the booting
	machine. After attempting the file as specified in the DHCP or
	hardcoded options, PXELINUX will probe the following paths, prefixed
	with "pxelinux.cfg/", under the initial current working directory:

	- The client UUID if provided by the PXE stack (note, some BIOSes don't
	have a valid UUID, and you might end up with something like all 1's.)
	This is in the standard UUID format using lower case hexadecimal digits,
	e.g. b8945908-d6a6-41a9-611d-74a6ab80b83d.

	- The hardware type (using its ARP type code) and address, all in lower
	case hexadecimal with dash separators; for example, for an Ethernet (ARP
	type 1) with address 88:99:AA:BB:CC:DD it would search for the filename
	01-88-99-aa-bb-cc-dd.

	- The client's IPv4 address in upper-case hexidecimal (ie 192.168.2.91
	-> C0A8025B; you can use the included progam "gethostip" to compute the
	hexadecimal IP address for any host.) followed by removing characters,
	one at a time, from the end.

	- "default"

	Starting in release 3.20, if PXELINUX can not find a configuration file,
	it will reboot after the timeout interval has expired. This keeps a
	machine from getting stuck indefinitely due to a boot server failure.


	== OPTIONS ==
	PXELINUX (starting with version 1.62) supports the following
	nonstandard DHCP options, which depending on your DHCP server you may be
	able to use to customize the specific behaviour of PXELINUX. See RFC
	5071 for some additional information about these options. Options for
	PXELINUX can be specified by DHCP options or hardcoded into the
	binary.

	=== Option Priority ===
	Hardcoded after-options are applied after DHCP options (and overrride)
	while hardcoded before-options are applied prior to DHCP options and
	default behavior takes the lowest priority.

	=== DHCP options ===
	Option 208 (pxelinux.magic)::
	Earlier versions of PXELINUX required this to be set to F1:00:74:7E
	(241.0.116.126) for PXELINUX to recognize any special DHCP options
	whatsoever. As of PXELINUX 3.55, this option is deprecated and is no
	longer required.

	Option 209 (pxelinux.configfile)::
	Specifies the initial PXELINUX configuration file name which may be
	qualified or unqualified.

	Option 210 (pxelinux.pathprefix)::
	Specifies the PXELINUX common path prefix, instead of deriving it from
	the boot file name. This almost certainly needs to end in whatever
	character the TFTP server OS uses as a pathname separator, e.g. slash
	(/) for Unix.

	Option 211 (pxelinux.reboottime)::
	Specifies, in seconds, the time to wait before reboot in the event of
	TFTP failure. 0 means wait "forever" (in reality, it waits
	approximately 136 years.)

	=== Hardcoded options ===
	Since version 3.83, the program "pxelinux-options" can be used to
	hard-code DHCP options into the pxelinux.0 image file; this is
	sometimes useful when the DHCP server is under different
	administrative control. Hardcoded options

	6 => 'domain-name-servers',
	15 => 'domain-name',
	54 => 'next-server',
	209 => 'config-file',
	210 => 'path-prefix',
	211 => 'reboottime'


	== HTTP/FTP ==
	Since version 5.10, a special PXELINUX binary, lpxelinux.0, natively
	supports HTTP and FTP transfers, greatly increasing load speed and
	allowing for standard HTTP scripts to present PXELINUX's configuration
	file. To use http or ftp, use standard URL syntax as filename; use the
	DHCP options below to transmit a suitable URL prefix to the client, or
	use the "pxelinux-options" tool provided in the utils directory to
	program it directly into the lpxelinux.0 file.


	== FILENAME SYNTAX ==
	//FIXME
	PXELINUX supports the following special pathname conventions:

	::filename::
	Suppresses the common filename prefix, i.e. passes the string "filename"
	unmodified to the server.

	IP address::filename (e.g. 192.168.2.3::filename)::
	Suppresses the common filename prefix, and sends a request to an alternate TFTP server. Instead of an IP address, a DNS name can be used. It will be assumed to be fully qualified if it contains dots; otherwise the local domain as reported by the DHCP server (option 15) will be added.

	:: was chosen because it is unlikely to conflict with operating system
	usage. However, if you happen to have an environment for which the
	special treatment of :: is a problem, please contact the Syslinux
	mailing list.

	Since version 4.00, PXELINUX also supports standard URL syntax.


	== KEEPPXE ==
	Normally, PXELINUX will unload the PXE and UNDI stacks before invoking
	the kernel. In special circumstances (for example, when using MEMDISK
	to boot an operating system with an UNDI network driver) it might be
	desirable to keep the PXE stack in memory. If the option "keeppxe"
	is given on the kernel command line, PXELINUX will keep the PXE and
	UNDI stacks in memory. (If you don't know what this means, you
	probably don't need it.)


	== EXAMPLES ==

	=== Configuration filename ===
	For DHCP siaddr 192.168.2.3, file 'mybootdir/pxelinux.0', client UUID
	b8945908-d6a6-41a9-611d-74a6ab80b83d, Ethernet MAC address
	88:99:AA:BB:CC:DD and IPv4 address 192.168.2.91, the following files in
	this order will be attempted (after config-file options):

	mybootdir/pxelinux.cfg/b8945908-d6a6-41a9-611d-74a6ab80b83d
	mybootdir/pxelinux.cfg/01-88-99-aa-bb-cc-dd
	mybootdir/pxelinux.cfg/C0A8025B
	mybootdir/pxelinux.cfg/C0A8025
	mybootdir/pxelinux.cfg/C0A802
	mybootdir/pxelinux.cfg/C0A80
	mybootdir/pxelinux.cfg/C0A8
	mybootdir/pxelinux.cfg/C0A
	mybootdir/pxelinux.cfg/C0
	mybootdir/pxelinux.cfg/C
	mybootdir/pxelinux.cfg/default


	=== TFTP servers ===
	For best results, use a TFTP server which supports the "tsize" TFTP
	option (RFC 1784/RFC 2349). The "tftp-hpa" TFTP server, which support
	options, is available at:

	http://www.kernel.org/pub/software/network/tftp/
	ftp://www.kernel.org/pub/software/network/tftp/

	and on any kernel.org mirror (see http://www.kernel.org/mirrors/).

	Another TFTP server which supports this is atftp by Jean-Pierre
	Lefebvre:

	ftp://ftp.mamalinux.com/pub/atftp/

	If your boot server is running Windows (and you can't fix that), try
	tftpd32 by Philippe Jounin (you need version 2.11 or later; previous
	versions had a bug which made it incompatible with PXELINUX):

	http://tftpd32.jounin.net/


	=== DHCP config: Simple ===
	The PXE protocol uses a very complex set of extensions to DHCP or
	BOOTP. However, most PXE implementations -- this includes all Intel
	ones version 0.99n and later -- seem to be able to boot in a
	"conventional" DHCP/TFTP configuration. Assuming you don't have to
	support any very old or otherwise severely broken clients, this is
	probably the best configuration unless you already have a PXE boot
	server on your network.

	A sample DHCP setup, using the "conventional TFTP" configuration,
	would look something like the following, using ISC dhcp 2.0 dhcpd.conf
	syntax:

	-----
	allow booting;
	allow bootp;

	# Standard configuration directives...

	option domain-name "<domain name>";
	option subnet-mask <subnet mask>;
	option broadcast-address <broadcast address>;
	option domain-name-servers <dns servers>;
	option routers <default router>;

	# Group the PXE bootable hosts together
	group {
	# PXE-specific configuration directives...
	next-server <TFTP server address>;
	filename "/tftpboot/pxelinux.0";

	# You need an entry like this for every host
	# unless you're using dynamic addresses
	host <hostname> {
	hardware ethernet <ethernet address>;
	fixed-address <hostname>;
	}
	}
	-----

	Note that if your particular TFTP daemon runs under chroot (tftp-hpa
	will do this if you specify the -s (secure) option; this is highly
	recommended), you almost certainly should not include the /tftpboot
	prefix in the filename statement.


	=== DHCP Config: PXE-1 ===
	If the simple config does not work for your environment, you probably
	should set up a "PXE boot server" on port 4011 of your TFTP server; a
	free PXE boot server is available at:

	http://www.kano.org.uk/projects/pxe/

	With such a boot server defined, your DHCP configuration should look
	the same except for an "option dhcp-class-identifier" ("option
	vendor-class-identifier" if you are using DHCP 3.0):

	----
	allow booting;
	allow bootp;

	# Standard configuration directives...

	option domain-name "<domain name>";
	option subnet-mask <subnet mask>;
	option broadcast-address <broadcast address>;
	option domain-name-servers <dns servers>;
	option routers <default router>;

	# Group the PXE bootable hosts together
	group {
	# PXE-specific configuration directives...
	option dhcp-class-identifier "PXEClient";
	next-server <pxe boot server address>;

	# You need an entry like this for every host
	# unless you're using dynamic addresses
	host <hostname> {
	hardware ethernet <ethernet address>;
	fixed-address <hostname>;
	}
	}
	----

	Here, the boot file name is obtained from the PXE server.


	=== DHCP Config: Encapsulated ===
	If the "conventional TFTP" configuration doesn't work on your clients,
	and setting up a PXE boot server is not an option, you can attempt the
	following configuration. It has been known to boot some
	configurations correctly; however, there are no guarantees:
	----
	allow booting;
	allow bootp;

	# Standard configuration directives...

	option domain-name "<domain name>";
	option subnet-mask <subnet mask>;
	option broadcast-address <broadcast address>;
	option domain-name-servers <dns servers>;
	option routers <default router>;

	# Group the PXE bootable hosts together
	group {
	# PXE-specific configuration directives...
	option dhcp-class-identifier "PXEClient";
	option vendor-encapsulated-options 09:0f:80:00:0c:4e:65:74:77:6f:72:6b:20:62:6f:6f:74:0a:07:00:50:72:6f:6d:70:74:06:01:02:08:03:80:00:00:47:04:80:00:00:00:ff;
	next-server <TFTP server>;
	filename "/tftpboot/pxelinux.0";

	# You need an entry like this for every host
	# unless you're using dynamic addresses
	host <hostname> {
	hardware ethernet <ethernet address>;
	fixed-address <hostname>;
	}
	}
	----
	Note that this will not boot some clients that will boot with the
	"conventional TFTP" configuration; Intel Boot Client 3.0 and later are
	known to fall into this category.


	=== DHCP Config: ISC dhcpd options ===
	ISC dhcp 3.0 supports a rather nice syntax for specifying custom
	options; you can use the following syntax in dhcpd.conf if you are
	running this version of dhcpd:
	----
	option space pxelinux;
	option pxelinux.magic code 208 = string;
	option pxelinux.configfile code 209 = text;
	option pxelinux.pathprefix code 210 = text;
	option pxelinux.reboottime code 211 = unsigned integer 32;
	----
	NOTE: In earlier versions of PXELINUX, this would only work as a
	"site-option-space". Since PXELINUX 2.07, this will work both as a
	"site-option-space" (unencapsulated) and as a "vendor-option-space"
	(type 43 encapsulated.) This may avoid messing with the
	dhcp-parameter-request-list, as detailed below.

	Then, inside your PXELINUX-booting group or class (whereever you have
	the PXELINUX-related options, such as the filename option), you can
	add, for example:
	----
	# Always include the following lines for all PXELINUX clients
	site-option-space "pxelinux";
	option pxelinux.magic f1:00:74:7e;
	if exists dhcp-parameter-request-list {
	# Always send the PXELINUX options (specified in hexadecimal)
	option dhcp-parameter-request-list = concat(option dhcp-parameter-request-list,d0,d1,d2,d3);
	}
	# These lines should be customized to your setup
	option pxelinux.configfile "configs/common";
	option pxelinux.pathprefix "/tftpboot/pxelinux/files/";
	option pxelinux.reboottime 30;
	filename "/tftpboot/pxelinux/pxelinux.bin";
	----
	Note that the configfile is relative to the pathprefix: this will look
	for a config file called /tftpboot/pxelinux/files/configs/common on
	the TFTP server.

	The "option dhcp-parameter-request-list" statement forces the DHCP
	server to send the PXELINUX-specific options, even though they are not
	explicitly requested. Since the DHCP request is done before PXELINUX
	is loaded, the PXE client won't know to request them.

	Using ISC dhcp 3.0 you can create a lot of these strings on the fly.
	For example, to use the hexadecimal form of the hardware address as
	the configuration file name, you could do something like:
	----
	site-option-space "pxelinux";
	option pxelinux.magic f1:00:74:7e;
	if exists dhcp-parameter-request-list {
	# Always send the PXELINUX options (specified in hexadecimal)
	option dhcp-parameter-request-list = concat(option dhcp-parameter-request-list,d0,d1,d2,d3);
	}
	option pxelinux.configfile =
	concat("pxelinux.cfg/", binary-to-ascii(16, 8, ":", hardware));
	filename "/tftpboot/pxelinux.bin";
	----
	If you used this from a client whose Ethernet address was
	58:FA:84:CF:55:0E, this would look for a configuration file named
	"/tftpboot/pxelinux.cfg/1:58:fa:84:cf:55:e".


	== KNOWN ISSUES ==
	The following problems are known with PXELINUX, so far:

	- The error recovery routine doesn't work quite right. For right now,
	it just does a hard reset - seems good enough.
	- We should probably call the UDP receive function in the keyboard
	entry loop, so that we answer ARP requests.
	- Boot sectors/disk images are not supported yet.

	If you have additional problems, please contact the Syslinux mailing
	list (see syslinux.txt for the address.)

	=== Broken PXE stacks ===
	Lots of PXE stacks, especially old ones, have various problems of
	varying degrees of severity. Please see:

	http://syslinux.zytor.com/hardware.php

	... for a list of currently known hardware problems, with workarounds
	if known.

	There are a number of extremely broken PXE stacks in the field. The
	gPXE project (formerly known as Etherboot) provides an open-source PXE
	stack that works with a number of cards, and which can be loaded from
	a CD-ROM, USB key, or floppy if desired.

	Information on gPXE is available from:

	http://www.etherboot.org/

	... and ready-to-use ROM or disk images from:

	http://www.rom-o-matic.net/

	Some cards, like may systems with the SiS 900, has a PXE stack which
	works just barely well enough to load a single file, but doesn't
	handle the more advanced items required by PXELINUX. If so, it is
	possible to use the built-in PXE stack to load gPXE, which can then
	load PXELINUX. See:

	http://www.etherboot.org/wiki/pxechaining


	== NOTES ==
	=== MTFTP ===
	PXELINUX does not support MTFTP, and there are no plans of doing so, as
	MTFTP is inherently broken for files more than 65535 packets (about 92
	MB) in size. It is of course possible to use MTFTP for the initial
	boot, if you have such a setup. MTFTP server setup is beyond the scope
	of this document.

	=== Error Recovery ===
	If the boot fails, PXELINUX (unlike SYSLINUX) will not wait forever;
	rather, if it has not received any input for approximately five
	minutes after displaying an error message, it will reset the machine.
	This allows an unattended machine to recover in case it had bad enough
	luck of trying to boot at the same time the TFTP server goes down.


	== SEE ALSO ==
	syslinux.cfg(5), syslinux-cli(1), lilo(8), keytab-lilo.pl(8),
	fdisk(8), mkfs(8), superformat(1).


	== AUTHOR ==
	This AsciiDoc derived document is a modified version of the original
	SYSLINUX documentation by {author} <{author-email}>. The conversion
	to an AsciiDoc was made by {editor1} <{editor1-email}>