[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.

     fdtoverlay_addr_r - location in RAM at which 'pxe boot' will temporarily store
     fdt overlay(s) before applying them to the fdt blob stored at 'fdt_addr_r'.

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)

fdtoverlays <path> [...] - if this label is chosen, use tftp to retrieve the DT
                      overlay(s) at <path>. it will be temporarily stored at the
                      address indicated in the fdtoverlay_addr_r environment variable,
                      and then applied in the load order to the fdt blob stored at the
                      address indicated in the fdt_addr_r environment variable.

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	91
69076dff NA	92	fdtoverlay_addr_r - location in RAM at which 'pxe boot' will temporarily store
	93	fdt overlay(s) before applying them to the fdt blob stored at 'fdt_addr_r'.
	94
06283a64 JH	95	pxe file format
	96	===============
	97	The pxe file format is nearly a subset of the PXELINUX file format; see
	98	http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
	99	commands - global commands, and commands specific to labels. Lines begining
	100	with # are treated as comments. White space between and at the beginning of
	101	lines is ignored.
	102
	103	The size of pxe files and the number of labels is only limited by the amount
a187559e	104	of RAM available to U-Boot. Memory for labels is dynamically allocated as
06283a64 JH	105	they're parsed, and memory for pxe files is statically allocated, and its
	106	location is given by the pxefile_addr_r environment variable. The pxe code is
	107	not aware of the size of the pxefile memory and will outgrow it if pxe files
	108	are too large.
	109
	110	Supported global commands
	111	-------------------------
	112	Unrecognized commands are ignored.
	113
6b62b9a3 WD	114	default <label> - the label named here is treated as the default and is
6b62b9a3 WD	115	the first label 'pxe boot' attempts to boot.
06283a64 JH	116
	117	menu title <string> - sets a title for the menu of labels being displayed.
	118
	119	menu include <path> - use tftp to retrieve the pxe file at <path>, which
6b62b9a3 WD	120	is then immediately parsed as if the start of its
	121	contents were the next line in the current file. nesting
	122	of include up to 16 files deep is supported.
06283a64	123
6b62b9a3 WD	124	prompt <flag> - if 1, always prompt the user to enter a label to boot
6b62b9a3 WD	125	from. if 0, only prompt the user if timeout expires.
06283a64 JH	126
06283a64 JH	127	timeout <num> - wait for user input for <num>/10 seconds before
6b62b9a3	128	auto-booting a node.
06283a64	129
6b62b9a3 WD	130	label <name> - begin a label definition. labels continue until
	131	a command not recognized as a label command is seen,
	132	or EOF is reached.
06283a64 JH	133
	134	Supported label commands
	135	------------------------
	136	labels end when a command not recognized as a label command is reached, or EOF.
	137
6b62b9a3 WD	138	menu default - set this label as the default label to boot; this is
	139	the same behavior as the global default command but
	140	specified in a different way
06283a64	141
6b62b9a3	142	kernel <path> - if this label is chosen, use tftp to retrieve the kernel
fce78503 WS	143	(or FIT image) at <path>. it will be stored at the address
	144	indicated in the kernel_addr_r environment variable, and
	145	that address will be passed to bootm to boot this kernel.
2023000a PD	146	For FIT image, The configuration specification can be
	147	appended to the file name, with the format:
	148	<path>#<conf>[#<extra-conf[#...]]
	149	It will passed to bootm with that address.
	150	(see: doc/uImage.FIT/command_syntax_extensions.txt)
	151	It useful for overlay selection in pxe file
	152	(see: doc/uImage.FIT/overlay-fdt-boot.txt)
06283a64	153
69076dff NA	154	fdtoverlays <path> [...] - if this label is chosen, use tftp to retrieve the DT
	155	overlay(s) at <path>. it will be temporarily stored at the
	156	address indicated in the fdtoverlay_addr_r environment variable,
	157	and then applied in the load order to the fdt blob stored at the
	158	address indicated in the fdt_addr_r environment variable.
	159
6b62b9a3 WD	160	append <string> - use <string> as the kernel command line when booting this
6b62b9a3 WD	161	label.
06283a64	162
6b62b9a3 WD	163	initrd <path> - if this label is chosen, use tftp to retrieve the initrd
	164	at <path>. it will be stored at the address indicated in
	165	the initrd_addr_r environment variable, and that address
	166	will be passed to bootm.
06283a64	167
a655938a CK	168	fdt <path> - if this label is chosen, use tftp to retrieve the fdt blob
	169	at <path>. it will be stored at the address indicated in
	170	the fdt_addr_r environment variable, and that address will
	171	be passed to bootm.
	172
6015f8f1 SB	173	fdtdir <path> - if this label is chosen, use tftp to retrieve a fdt blob
	174	relative to <path>. If the fdtfile environment variable
	175	is set, <path>/<fdtfile> is retrieved. Otherwise, the
	176	filename is generated from the soc and board environment
	177	variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
	178	If the fdt command is specified, fdtdir is ignored.
	179
06283a64	180	localboot <flag> - Run the command defined by "localcmd" in the environment.
6b62b9a3 WD	181	<flag> is ignored and is only here to match the syntax of
6b62b9a3 WD	182	PXELINUX config files.
06283a64 JH	183
	184	Example
	185	-------
	186	Here's a couple of example files to show how this works.
	187
695c1329	188	------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
06283a64 JH	189	menu title Linux selections
	190
	191	# This is the default label
	192	label install
	193	menu label Default Install Image
	194	kernel kernels/install.bin
	195	append console=ttyAMA0,38400 debug earlyprintk
	196	initrd initrds/uzInitrdDebInstall
	197
	198	# Just another label
	199	label linux-2.6.38
	200	kernel kernels/linux-2.6.38.bin
	201	append root=/dev/sdb1
	202
	203	# The locally installed kernel
	204	label local
	205	menu label Locally installed kernel
	206	append root=/dev/sdb1
	207	localboot 1
	208	-------------------------------------------------------------
	209
	210	------------/tftpboot/pxelinux.cfg/default-------------------
	211	menu include pxelinux.cfg/menus/base.menu
	212	timeout 500
	213
	214	default linux-2.6.38
	215	-------------------------------------------------------------
	216
	217	When a pxe client retrieves and boots the default pxe file,
	218	'pxe boot' will wait for user input for 5 seconds before booting
	219	the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
	220	to be downloaded, and boot with the command line "root=/dev/sdb1"
	221
	222	Differences with PXELINUX
	223	=========================
a187559e BM	224	The biggest difference between U-Boot's pxe and PXELINUX is that since
	225	U-Boot's pxe support is written entirely in C, it can run on any platform
	226	with network support in U-Boot. Here are some other differences between
	227	PXELINUX and U-Boot's pxe support.
06283a64	228
a187559e	229	- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
06283a64 JH	230	in RFC 5071, but could be extended to do so.
06283a64 JH	231
a187559e BM	232	- when U-Boot's pxe fails to boot, it will return control to U-Boot,
a187559e BM	233	allowing another command to run, other U-Boot command, instead of resetting
06283a64 JH	234	the machine like PXELINUX.
06283a64 JH	235
a187559e BM	236	- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
a187559e BM	237	only uses U-Boot.
06283a64	238
a187559e	239	- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
06283a64	240	does, only a simple text based menu using the commands described in
6b62b9a3	241	this README. With PXELINUX, it's possible to have a graphical boot
a187559e	242	menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
06283a64 JH	243	a more robust menuing system like that of PXELINUX's.
06283a64 JH	244
a187559e BM	245	- U-Boot's pxe expects U-Boot uimg's as kernels. Anything that would work
a187559e BM	246	with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
06283a64	247
a187559e	248	- U-Boot's pxe only recognizes a single file on the initrd command line. It
06283a64 JH	249	could be extended to support multiple.
06283a64 JH	250
a187559e	251	- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
06283a64 JH	252	disk boot - it will do whatever is defined in the 'localcmd' env
	253	variable. And since it doesn't support a full UNDI/PXE stack, the
	254	type field is ignored.
	255
a187559e	256	- the interactive prompt in U-Boot's pxe only allows you to choose a label
06283a64	257	from the menu. If you want to boot something not listed, you can ctrl+c
a187559e	258	out of 'pxe boot' and use existing U-Boot commands to accomplish it.