[thirdparty/u-boot.git] / doc / README.pxe

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

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.
		      For FIT image, The configuration specification can be
		      appended to the file name, with the format:
		        <path>#<conf>[#<extra-conf[#...]]
		      It will passed to bootm with that address.
		      (see: doc/uImage.FIT/command_syntax_extensions.txt)
		      It useful for overlay selection in pxe file
		      (see: doc/uImage.FIT/overlay-fdt-boot.txt)

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
83d290c5	1	SPDX-License-Identifier: GPL-2.0+
06283a64 JH	2	/*
06283a64 JH	3	* Copyright 2010-2011 Calxeda, Inc.
06283a64 JH	4	*/
	5
	6	The 'pxe' commands provide a near subset of the functionality provided by
a187559e BM	7	the PXELINUX boot loader. This allows U-Boot based systems to be controlled
a187559e BM	8	remotely using the same PXE based techniques that many non U-Boot based servers
06283a64 JH	9	use.
	10
	11	Commands
	12	========
	13
	14	pxe get
	15	-------
	16	syntax: pxe get
	17
	18	follows PXELINUX's rules for retrieving configuration files from a tftp
	19	server, and supports a subset of PXELINUX's config file syntax.
	20
	21	Environment
	22	-----------
	23	'pxe get' requires two environment variables to be set:
	24
	25	pxefile_addr_r - should be set to a location in RAM large enough to hold
	26	pxe files while they're being processed. Up to 16 config files may be
	27	held in memory at once. The exact number and size of the files varies with
	28	how the system is being used. A typical config file is a few hundred bytes
	29	long.
	30
	31	bootfile,serverip - these two are typically set in the DHCP response
	32	handler, and correspond to fields in the DHCP response.
	33
	34	'pxe get' optionally supports these two environment variables being set:
	35
	36	ethaddr - this is the standard MAC address for the ethernet adapter in use.
	37	'pxe get' uses it to look for a configuration file specific to a system's
	38	MAC address.
	39
	40	pxeuuid - this is a UUID in standard form using lower case hexadecimal
	41	digits, for example, 550e8400-e29b-41d4-a716-446655440000. 'pxe get' uses
	42	it to look for a configuration file based on the system's UUID.
	43
	44	File Paths
	45	----------
	46	'pxe get' repeatedly tries to download config files until it either
	47	successfully downloads one or runs out of paths to try. The order and
	48	contents of paths it tries mirrors exactly that of PXELINUX - you can
	49	read in more detail about it at:
	50
	51	http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux
	52
	53	pxe boot
	54	--------
	55	syntax: pxe boot [pxefile_addr_r]
	56
	57	Interprets a pxe file stored in memory.
	58
	59	pxefile_addr_r is an optional argument giving the location of the pxe file.
	60	The file must be terminated with a NUL byte.
	61
	62	Environment
	63	-----------
	64	There are some environment variables that may need to be set, depending
	65	on conditions.
	66
	67	pxefile_addr_r - if the optional argument pxefile_addr_r is not supplied,
	68	an environment variable named pxefile_addr_r must be supplied. This is
	69	typically the same value as is used for the 'pxe get' command.
	70
	71	bootfile - typically set in the DHCP response handler based on the
	72	same field in the DHCP respone, this path is used to generate the base
73	directory that all other paths to files retrieved by 'pxe boot' will use.
74	If no bootfile is specified, paths used in pxe files will be used as is.
75
76	serverip - typically set in the DHCP response handler, this is the IP
77	address of the tftp server from which other files will be retrieved.
78
79	kernel_addr_r, initrd_addr_r - locations in RAM at which 'pxe boot' will
fce78503 WS	80	store the kernel(or FIT image) and initrd it retrieves from tftp. These
	81	locations will be passed to the bootm command to boot the kernel. These
	82	environment variables are required to be set.
06283a64	83
a655938a CK	84	fdt_addr_r - location in RAM at which 'pxe boot' will store the fdt blob it
	85	retrieves from tftp. The retrieval is possible if 'fdt' label is defined in
	86	pxe file and 'fdt_addr_r' is set. If retrieval is possible, 'fdt_addr_r'
	87	will be passed to bootm command to boot the kernel.
	88
	89	fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
	90	command if it is set and 'fdt_addr_r' is not passed to bootm command.
06283a64 JH	91
	92	pxe file format
	93	===============
	94	The pxe file format is nearly a subset of the PXELINUX file format; see
	95	http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
	96	commands - global commands, and commands specific to labels. Lines begining
	97	with # are treated as comments. White space between and at the beginning of
	98	lines is ignored.
	99
	100	The size of pxe files and the number of labels is only limited by the amount
a187559e	101	of RAM available to U-Boot. Memory for labels is dynamically allocated as
06283a64 JH	102	they're parsed, and memory for pxe files is statically allocated, and its
	103	location is given by the pxefile_addr_r environment variable. The pxe code is
	104	not aware of the size of the pxefile memory and will outgrow it if pxe files
	105	are too large.
	106
	107	Supported global commands
	108	-------------------------
	109	Unrecognized commands are ignored.
	110
6b62b9a3 WD	111	default <label> - the label named here is treated as the default and is
6b62b9a3 WD	112	the first label 'pxe boot' attempts to boot.
06283a64 JH	113
	114	menu title <string> - sets a title for the menu of labels being displayed.
	115
	116	menu include <path> - use tftp to retrieve the pxe file at <path>, which
6b62b9a3 WD	117	is then immediately parsed as if the start of its
	118	contents were the next line in the current file. nesting
	119	of include up to 16 files deep is supported.
06283a64	120
6b62b9a3 WD	121	prompt <flag> - if 1, always prompt the user to enter a label to boot
6b62b9a3 WD	122	from. if 0, only prompt the user if timeout expires.
06283a64 JH	123
06283a64 JH	124	timeout <num> - wait for user input for <num>/10 seconds before
6b62b9a3	125	auto-booting a node.
06283a64	126
6b62b9a3 WD	127	label <name> - begin a label definition. labels continue until
	128	a command not recognized as a label command is seen,
	129	or EOF is reached.
06283a64 JH	130
	131	Supported label commands
	132	------------------------
	133	labels end when a command not recognized as a label command is reached, or EOF.
	134
6b62b9a3 WD	135	menu default - set this label as the default label to boot; this is
	136	the same behavior as the global default command but
	137	specified in a different way
06283a64	138
6b62b9a3	139	kernel <path> - if this label is chosen, use tftp to retrieve the kernel
fce78503 WS	140	(or FIT image) at <path>. it will be stored at the address
	141	indicated in the kernel_addr_r environment variable, and
	142	that address will be passed to bootm to boot this kernel.
2023000a PD	143	For FIT image, The configuration specification can be
	144	appended to the file name, with the format:
	145	<path>#<conf>[#<extra-conf[#...]]
	146	It will passed to bootm with that address.
	147	(see: doc/uImage.FIT/command_syntax_extensions.txt)
	148	It useful for overlay selection in pxe file
	149	(see: doc/uImage.FIT/overlay-fdt-boot.txt)
06283a64	150
6b62b9a3 WD	151	append <string> - use <string> as the kernel command line when booting this
6b62b9a3 WD	152	label.
06283a64	153
6b62b9a3 WD	154	initrd <path> - if this label is chosen, use tftp to retrieve the initrd
	155	at <path>. it will be stored at the address indicated in
	156	the initrd_addr_r environment variable, and that address
	157	will be passed to bootm.
06283a64	158
a655938a CK	159	fdt <path> - if this label is chosen, use tftp to retrieve the fdt blob
	160	at <path>. it will be stored at the address indicated in
	161	the fdt_addr_r environment variable, and that address will
	162	be passed to bootm.
	163
6015f8f1 SB	164	fdtdir <path> - if this label is chosen, use tftp to retrieve a fdt blob
	165	relative to <path>. If the fdtfile environment variable
	166	is set, <path>/<fdtfile> is retrieved. Otherwise, the
	167	filename is generated from the soc and board environment
	168	variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
	169	If the fdt command is specified, fdtdir is ignored.
	170
06283a64	171	localboot <flag> - Run the command defined by "localcmd" in the environment.
6b62b9a3 WD	172	<flag> is ignored and is only here to match the syntax of
6b62b9a3 WD	173	PXELINUX config files.
06283a64 JH	174
	175	Example
	176	-------
	177	Here's a couple of example files to show how this works.
	178
695c1329	179	------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
06283a64 JH	180	menu title Linux selections
	181
	182	# This is the default label
	183	label install
	184	menu label Default Install Image
	185	kernel kernels/install.bin
	186	append console=ttyAMA0,38400 debug earlyprintk
	187	initrd initrds/uzInitrdDebInstall
	188
	189	# Just another label
	190	label linux-2.6.38
	191	kernel kernels/linux-2.6.38.bin
	192	append root=/dev/sdb1
	193
	194	# The locally installed kernel
	195	label local
	196	menu label Locally installed kernel
	197	append root=/dev/sdb1
	198	localboot 1
	199	-------------------------------------------------------------
	200
	201	------------/tftpboot/pxelinux.cfg/default-------------------
	202	menu include pxelinux.cfg/menus/base.menu
	203	timeout 500
	204
	205	default linux-2.6.38
	206	-------------------------------------------------------------
	207
	208	When a pxe client retrieves and boots the default pxe file,
	209	'pxe boot' will wait for user input for 5 seconds before booting
	210	the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
	211	to be downloaded, and boot with the command line "root=/dev/sdb1"
	212
	213	Differences with PXELINUX
	214	=========================
a187559e BM	215	The biggest difference between U-Boot's pxe and PXELINUX is that since
	216	U-Boot's pxe support is written entirely in C, it can run on any platform
	217	with network support in U-Boot. Here are some other differences between
	218	PXELINUX and U-Boot's pxe support.
06283a64	219
a187559e	220	- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
06283a64 JH	221	in RFC 5071, but could be extended to do so.
06283a64 JH	222
a187559e BM	223	- when U-Boot's pxe fails to boot, it will return control to U-Boot,
a187559e BM	224	allowing another command to run, other U-Boot command, instead of resetting
06283a64 JH	225	the machine like PXELINUX.
06283a64 JH	226
a187559e BM	227	- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
a187559e BM	228	only uses U-Boot.
06283a64	229
a187559e	230	- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
06283a64	231	does, only a simple text based menu using the commands described in
6b62b9a3	232	this README. With PXELINUX, it's possible to have a graphical boot
a187559e	233	menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
06283a64 JH	234	a more robust menuing system like that of PXELINUX's.
06283a64 JH	235
a187559e BM	236	- U-Boot's pxe expects U-Boot uimg's as kernels. Anything that would work
a187559e BM	237	with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
06283a64	238
a187559e	239	- U-Boot's pxe only recognizes a single file on the initrd command line. It
06283a64 JH	240	could be extended to support multiple.
06283a64 JH	241
a187559e	242	- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
06283a64 JH	243	disk boot - it will do whatever is defined in the 'localcmd' env
	244	variable. And since it doesn't support a full UNDI/PXE stack, the
	245	type field is ignored.
	246
a187559e	247	- the interactive prompt in U-Boot's pxe only allows you to choose a label
06283a64	248	from the menu. If you want to boot something not listed, you can ctrl+c
a187559e	249	out of 'pxe boot' and use existing U-Boot commands to accomplish it.