[people/ms/u-boot.git] / doc / README.pxe

/*
 * Copyright 2010-2011 Calxeda, Inc.
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

The 'pxe' commands provide a near subset of the functionality provided by
the PXELINUX boot loader. This allows U-Boot based systems to be controlled
remotely using the same PXE based techniques that many non U-Boot based servers
use.

Commands
========

pxe get
-------
     syntax: pxe get

     follows PXELINUX's rules for retrieving configuration files from a tftp
     server, and supports a subset of PXELINUX's config file syntax.

     Environment
     -----------
     'pxe get' requires two environment variables to be set:

     pxefile_addr_r - should be set to a location in RAM large enough to hold
     pxe files while they're being processed. Up to 16 config files may be
     held in memory at once. The exact number and size of the files varies with
     how the system is being used. A typical config file is a few hundred bytes
     long.

     bootfile,serverip - these two are typically set in the DHCP response
     handler, and correspond to fields in the DHCP response.

     'pxe get' optionally supports these two environment variables being set:

     ethaddr - this is the standard MAC address for the ethernet adapter in use.
     'pxe get' uses it to look for a configuration file specific to a system's
     MAC address.

     pxeuuid - this is a UUID in standard form using lower case hexadecimal
     digits, for example, 550e8400-e29b-41d4-a716-446655440000. 'pxe get' uses
     it to look for a configuration file based on the system's UUID.

     File Paths
     ----------
     'pxe get' repeatedly tries to download config files until it either
     successfully downloads one or runs out of paths to try. The order and
     contents of paths it tries mirrors exactly that of PXELINUX - you can
     read in more detail about it at:

     http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux

pxe boot
--------
     syntax: pxe boot [pxefile_addr_r]

     Interprets a pxe file stored in memory.

     pxefile_addr_r is an optional argument giving the location of the pxe file.
     The file must be terminated with a NUL byte.

     Environment
     -----------
     There are some environment variables that may need to be set, depending
     on conditions.

     pxefile_addr_r - if the optional argument pxefile_addr_r is not supplied,
     an environment variable named pxefile_addr_r must be supplied. This is
     typically the same value as is used for the 'pxe get' command.

     bootfile - typically set in the DHCP response handler based on the
     same field in the DHCP respone, this path is used to generate the base
     directory that all other paths to files retrieved by 'pxe boot' will use.
     If no bootfile is specified, paths used in pxe files will be used as is.

     serverip - typically set in the DHCP response handler, this is the IP
     address of the tftp server from which other files will be retrieved.

     kernel_addr_r, initrd_addr_r - locations in RAM at which 'pxe boot' will
     store the kernel(or FIT image) and initrd it retrieves from tftp. These
     locations will be passed to the bootm command to boot the kernel. These
     environment variables are required to be set.

     fdt_addr_r - location in RAM at which 'pxe boot' will store the fdt blob it
     retrieves from tftp. The retrieval is possible if 'fdt' label is defined in
     pxe file and 'fdt_addr_r' is set. If retrieval is possible, 'fdt_addr_r'
     will be passed to bootm command to boot the kernel.

     fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
     command if it is set and 'fdt_addr_r' is not passed to bootm command.

pxe file format
===============
The pxe file format is nearly a subset of the PXELINUX file format; see
http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
commands - global commands, and commands specific to labels. Lines begining
with # are treated as comments. White space between and at the beginning of
lines is ignored.

The size of pxe files and the number of labels is only limited by the amount
of RAM available to U-Boot. Memory for labels is dynamically allocated as
they're parsed, and memory for pxe files is statically allocated, and its
location is given by the pxefile_addr_r environment variable. The pxe code is
not aware of the size of the pxefile memory and will outgrow it if pxe files
are too large.

Supported global commands
-------------------------
Unrecognized commands are ignored.

default <label>	    - the label named here is treated as the default and is
		      the first label 'pxe boot' attempts to boot.

menu title <string> - sets a title for the menu of labels being displayed.

menu include <path> - use tftp to retrieve the pxe file at <path>, which
		      is then immediately parsed as if the start of its
		      contents were the next line in the current file. nesting
		      of include up to 16 files deep is supported.

prompt <flag>	    - if 1, always prompt the user to enter a label to boot
		      from. if 0, only prompt the user if timeout expires.

timeout <num>	    - wait for user input for <num>/10 seconds before
		      auto-booting a node.

label <name>	    - begin a label definition. labels continue until
		      a command not recognized as a label command is seen,
		      or EOF is reached.

Supported label commands
------------------------
labels end when a command not recognized as a label command is reached, or EOF.

menu default	    - set this label as the default label to boot; this is
		      the same behavior as the global default command but
		      specified in a different way

kernel <path>	    - if this label is chosen, use tftp to retrieve the kernel
		      (or FIT image) at <path>. it will be stored at the address
		      indicated in the kernel_addr_r environment variable, and
		      that address will be passed to bootm to boot this kernel.

append <string>	    - use <string> as the kernel command line when booting this
		      label.

initrd <path>	    - if this label is chosen, use tftp to retrieve the initrd
		      at <path>. it will be stored at the address indicated in
		      the initrd_addr_r environment variable, and that address
		      will be passed to bootm.

fdt <path>	    - if this label is chosen, use tftp to retrieve the fdt blob
		      at <path>. it will be stored at the address indicated in
		      the fdt_addr_r environment variable, and that address will
		      be passed to bootm.

fdtdir <path>	    - if this label is chosen, use tftp to retrieve a fdt blob
		      relative to <path>. If the fdtfile environment variable
		      is set, <path>/<fdtfile> is retrieved. Otherwise, the
		      filename is generated from the soc and board environment
		      variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
		      If the fdt command is specified, fdtdir is ignored.

localboot <flag>    - Run the command defined by "localcmd" in the environment.
		      <flag> is ignored and is only here to match the syntax of
		      PXELINUX config files.

Example
-------
Here's a couple of example files to show how this works.

------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
menu title Linux selections

# This is the default label
label install
	menu label Default Install Image
	kernel kernels/install.bin
	append console=ttyAMA0,38400 debug earlyprintk
	initrd initrds/uzInitrdDebInstall

# Just another label
label linux-2.6.38
	kernel kernels/linux-2.6.38.bin
	append root=/dev/sdb1

# The locally installed kernel
label local
	menu label Locally installed kernel
	append root=/dev/sdb1
	localboot 1
-------------------------------------------------------------

------------/tftpboot/pxelinux.cfg/default-------------------
menu include pxelinux.cfg/menus/base.menu
timeout 500

default linux-2.6.38
-------------------------------------------------------------

When a pxe client retrieves and boots the default pxe file,
'pxe boot' will wait for user input for 5 seconds before booting
the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
to be downloaded, and boot with the command line "root=/dev/sdb1"

Differences with PXELINUX
=========================
The biggest difference between U-Boot's pxe and PXELINUX is that since
U-Boot's pxe support is written entirely in C, it can run on any platform
with network support in U-Boot. Here are some other differences between
PXELINUX and U-Boot's pxe support.

- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
  in RFC 5071, but could be extended to do so.

- when U-Boot's pxe fails to boot, it will return control to U-Boot,
  allowing another command to run, other U-Boot command, instead of resetting
  the machine like PXELINUX.

- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
  only uses U-Boot.

- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
  does, only a simple text based menu using the commands described in
  this README.	With PXELINUX, it's possible to have a graphical boot
  menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
  a more robust menuing system like that of PXELINUX's.

- U-Boot's pxe expects U-Boot uimg's as kernels.  Anything that would work
  with the 'bootm' command in U-Boot could work with the 'pxe boot' command.

- U-Boot's pxe only recognizes a single file on the initrd command line.  It
  could be extended to support multiple.

- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
  disk boot - it will do whatever is defined in the 'localcmd' env
  variable. And since it doesn't support a full UNDI/PXE stack, the
  type field is ignored.

- the interactive prompt in U-Boot's pxe only allows you to choose a label
  from the menu.  If you want to boot something not listed, you can ctrl+c
  out of 'pxe boot' and use existing U-Boot commands to accomplish it.
Commit	Line	Data
06283a64 JH	1	/*
	2	* Copyright 2010-2011 Calxeda, Inc.
	3	*
1a459660	4	* SPDX-License-Identifier: GPL-2.0+
06283a64 JH	5	*/
	6
	7	The 'pxe' commands provide a near subset of the functionality provided by
a187559e BM	8	the PXELINUX boot loader. This allows U-Boot based systems to be controlled
a187559e BM	9	remotely using the same PXE based techniques that many non U-Boot based servers
06283a64 JH	10	use.
	11
	12	Commands
	13	========
	14
	15	pxe get
	16	-------
	17	syntax: pxe get
	18
	19	follows PXELINUX's rules for retrieving configuration files from a tftp
	20	server, and supports a subset of PXELINUX's config file syntax.
	21
	22	Environment
	23	-----------
	24	'pxe get' requires two environment variables to be set:
	25
	26	pxefile_addr_r - should be set to a location in RAM large enough to hold
	27	pxe files while they're being processed. Up to 16 config files may be
	28	held in memory at once. The exact number and size of the files varies with
	29	how the system is being used. A typical config file is a few hundred bytes
	30	long.
	31
	32	bootfile,serverip - these two are typically set in the DHCP response
	33	handler, and correspond to fields in the DHCP response.
	34
	35	'pxe get' optionally supports these two environment variables being set:
	36
	37	ethaddr - this is the standard MAC address for the ethernet adapter in use.
	38	'pxe get' uses it to look for a configuration file specific to a system's
	39	MAC address.
	40
	41	pxeuuid - this is a UUID in standard form using lower case hexadecimal
	42	digits, for example, 550e8400-e29b-41d4-a716-446655440000. 'pxe get' uses
	43	it to look for a configuration file based on the system's UUID.
	44
	45	File Paths
	46	----------
	47	'pxe get' repeatedly tries to download config files until it either
	48	successfully downloads one or runs out of paths to try. The order and
	49	contents of paths it tries mirrors exactly that of PXELINUX - you can
	50	read in more detail about it at:
	51
	52	http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux
	53
	54	pxe boot
	55	--------
	56	syntax: pxe boot [pxefile_addr_r]
	57
	58	Interprets a pxe file stored in memory.
	59
	60	pxefile_addr_r is an optional argument giving the location of the pxe file.
	61	The file must be terminated with a NUL byte.
	62
	63	Environment
	64	-----------
	65	There are some environment variables that may need to be set, depending
	66	on conditions.
	67
	68	pxefile_addr_r - if the optional argument pxefile_addr_r is not supplied,
	69	an environment variable named pxefile_addr_r must be supplied. This is
	70	typically the same value as is used for the 'pxe get' command.
	71
	72	bootfile - typically set in the DHCP response handler based on the
	73	same field in the DHCP respone, this path is used to generate the base
74	directory that all other paths to files retrieved by 'pxe boot' will use.
75	If no bootfile is specified, paths used in pxe files will be used as is.
76
77	serverip - typically set in the DHCP response handler, this is the IP
78	address of the tftp server from which other files will be retrieved.
79
80	kernel_addr_r, initrd_addr_r - locations in RAM at which 'pxe boot' will
fce78503 WS	81	store the kernel(or FIT image) and initrd it retrieves from tftp. These
	82	locations will be passed to the bootm command to boot the kernel. These
	83	environment variables are required to be set.
06283a64	84
a655938a CK	85	fdt_addr_r - location in RAM at which 'pxe boot' will store the fdt blob it
	86	retrieves from tftp. The retrieval is possible if 'fdt' label is defined in
	87	pxe file and 'fdt_addr_r' is set. If retrieval is possible, 'fdt_addr_r'
	88	will be passed to bootm command to boot the kernel.
	89
	90	fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
	91	command if it is set and 'fdt_addr_r' is not passed to bootm command.
06283a64 JH	92
	93	pxe file format
	94	===============
	95	The pxe file format is nearly a subset of the PXELINUX file format; see
	96	http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
	97	commands - global commands, and commands specific to labels. Lines begining
	98	with # are treated as comments. White space between and at the beginning of
	99	lines is ignored.
	100
	101	The size of pxe files and the number of labels is only limited by the amount
a187559e	102	of RAM available to U-Boot. Memory for labels is dynamically allocated as
06283a64 JH	103	they're parsed, and memory for pxe files is statically allocated, and its
	104	location is given by the pxefile_addr_r environment variable. The pxe code is
	105	not aware of the size of the pxefile memory and will outgrow it if pxe files
	106	are too large.
	107
	108	Supported global commands
	109	-------------------------
	110	Unrecognized commands are ignored.
	111
6b62b9a3 WD	112	default <label> - the label named here is treated as the default and is
6b62b9a3 WD	113	the first label 'pxe boot' attempts to boot.
06283a64 JH	114
	115	menu title <string> - sets a title for the menu of labels being displayed.
	116
	117	menu include <path> - use tftp to retrieve the pxe file at <path>, which
6b62b9a3 WD	118	is then immediately parsed as if the start of its
	119	contents were the next line in the current file. nesting
	120	of include up to 16 files deep is supported.
06283a64	121
6b62b9a3 WD	122	prompt <flag> - if 1, always prompt the user to enter a label to boot
6b62b9a3 WD	123	from. if 0, only prompt the user if timeout expires.
06283a64 JH	124
06283a64 JH	125	timeout <num> - wait for user input for <num>/10 seconds before
6b62b9a3	126	auto-booting a node.
06283a64	127
6b62b9a3 WD	128	label <name> - begin a label definition. labels continue until
	129	a command not recognized as a label command is seen,
	130	or EOF is reached.
06283a64 JH	131
	132	Supported label commands
	133	------------------------
	134	labels end when a command not recognized as a label command is reached, or EOF.
	135
6b62b9a3 WD	136	menu default - set this label as the default label to boot; this is
	137	the same behavior as the global default command but
	138	specified in a different way
06283a64	139
6b62b9a3	140	kernel <path> - if this label is chosen, use tftp to retrieve the kernel
fce78503 WS	141	(or FIT image) at <path>. it will be stored at the address
	142	indicated in the kernel_addr_r environment variable, and
	143	that address will be passed to bootm to boot this kernel.
06283a64	144
6b62b9a3 WD	145	append <string> - use <string> as the kernel command line when booting this
6b62b9a3 WD	146	label.
06283a64	147
6b62b9a3 WD	148	initrd <path> - if this label is chosen, use tftp to retrieve the initrd
	149	at <path>. it will be stored at the address indicated in
	150	the initrd_addr_r environment variable, and that address
	151	will be passed to bootm.
06283a64	152
a655938a CK	153	fdt <path> - if this label is chosen, use tftp to retrieve the fdt blob
	154	at <path>. it will be stored at the address indicated in
	155	the fdt_addr_r environment variable, and that address will
	156	be passed to bootm.
	157
6015f8f1 SB	158	fdtdir <path> - if this label is chosen, use tftp to retrieve a fdt blob
	159	relative to <path>. If the fdtfile environment variable
	160	is set, <path>/<fdtfile> is retrieved. Otherwise, the
	161	filename is generated from the soc and board environment
	162	variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
	163	If the fdt command is specified, fdtdir is ignored.
	164
06283a64	165	localboot <flag> - Run the command defined by "localcmd" in the environment.
6b62b9a3 WD	166	<flag> is ignored and is only here to match the syntax of
6b62b9a3 WD	167	PXELINUX config files.
06283a64 JH	168
	169	Example
	170	-------
	171	Here's a couple of example files to show how this works.
	172
695c1329	173	------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
06283a64 JH	174	menu title Linux selections
	175
	176	# This is the default label
	177	label install
	178	menu label Default Install Image
	179	kernel kernels/install.bin
	180	append console=ttyAMA0,38400 debug earlyprintk
	181	initrd initrds/uzInitrdDebInstall
	182
	183	# Just another label
	184	label linux-2.6.38
	185	kernel kernels/linux-2.6.38.bin
	186	append root=/dev/sdb1
	187
	188	# The locally installed kernel
	189	label local
	190	menu label Locally installed kernel
	191	append root=/dev/sdb1
	192	localboot 1
	193	-------------------------------------------------------------
	194
	195	------------/tftpboot/pxelinux.cfg/default-------------------
	196	menu include pxelinux.cfg/menus/base.menu
	197	timeout 500
	198
	199	default linux-2.6.38
	200	-------------------------------------------------------------
	201
	202	When a pxe client retrieves and boots the default pxe file,
	203	'pxe boot' will wait for user input for 5 seconds before booting
	204	the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
	205	to be downloaded, and boot with the command line "root=/dev/sdb1"
	206
	207	Differences with PXELINUX
	208	=========================
a187559e BM	209	The biggest difference between U-Boot's pxe and PXELINUX is that since
	210	U-Boot's pxe support is written entirely in C, it can run on any platform
	211	with network support in U-Boot. Here are some other differences between
	212	PXELINUX and U-Boot's pxe support.
06283a64	213
a187559e	214	- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
06283a64 JH	215	in RFC 5071, but could be extended to do so.
06283a64 JH	216
a187559e BM	217	- when U-Boot's pxe fails to boot, it will return control to U-Boot,
a187559e BM	218	allowing another command to run, other U-Boot command, instead of resetting
06283a64 JH	219	the machine like PXELINUX.
06283a64 JH	220
a187559e BM	221	- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
a187559e BM	222	only uses U-Boot.
06283a64	223
a187559e	224	- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
06283a64	225	does, only a simple text based menu using the commands described in
6b62b9a3	226	this README. With PXELINUX, it's possible to have a graphical boot
a187559e	227	menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
06283a64 JH	228	a more robust menuing system like that of PXELINUX's.
06283a64 JH	229
a187559e BM	230	- U-Boot's pxe expects U-Boot uimg's as kernels. Anything that would work
a187559e BM	231	with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
06283a64	232
a187559e	233	- U-Boot's pxe only recognizes a single file on the initrd command line. It
06283a64 JH	234	could be extended to support multiple.
06283a64 JH	235
a187559e	236	- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
06283a64 JH	237	disk boot - it will do whatever is defined in the 'localcmd' env
	238	variable. And since it doesn't support a full UNDI/PXE stack, the
	239	type field is ignored.
	240
a187559e	241	- the interactive prompt in U-Boot's pxe only allows you to choose a label
06283a64	242	from the menu. If you want to boot something not listed, you can ctrl+c
a187559e	243	out of 'pxe boot' and use existing U-Boot commands to accomplish it.