[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_label_override - override label to be used, if exists, instead of the
     default label. This will allow consumers to choose a pxe label at
     runtime instead of having to prompt the user. If "pxe_label_override" is set
     but does not exist in the pxe menu, pxe would fallback to the default label if
     given, and no failure is returned but rather a warning message.

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.

devicetree-overlay <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.
                      Alias for fdtoverlays.

kaslrseed           - set this label to request random number from hwrng as kaslr seed.

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.
		      For FIT image, the initrd can be provided with the same value than
		      kernel, including configuration:
		        <path>#<conf>[#<extra-conf[#...]]
		      In this case, kernel_addr_r is 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.
		      For FIT image, the device tree can be provided with the same value
		      than kernel, including configuration:
		        <path>#<conf>[#<extra-conf[#...]]
		      In this case, kernel_addr_r is passed to bootm.

devicetree <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. Alias for fdt.

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
c2969792 AOA	95	pxe_label_override - override label to be used, if exists, instead of the
	96	default label. This will allow consumers to choose a pxe label at
	97	runtime instead of having to prompt the user. If "pxe_label_override" is set
	98	but does not exist in the pxe menu, pxe would fallback to the default label if
	99	given, and no failure is returned but rather a warning message.
	100
06283a64 JH	101	pxe file format
	102	===============
	103	The pxe file format is nearly a subset of the PXELINUX file format; see
	104	http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
	105	commands - global commands, and commands specific to labels. Lines begining
	106	with # are treated as comments. White space between and at the beginning of
	107	lines is ignored.
	108
	109	The size of pxe files and the number of labels is only limited by the amount
a187559e	110	of RAM available to U-Boot. Memory for labels is dynamically allocated as
06283a64 JH	111	they're parsed, and memory for pxe files is statically allocated, and its
	112	location is given by the pxefile_addr_r environment variable. The pxe code is
	113	not aware of the size of the pxefile memory and will outgrow it if pxe files
	114	are too large.
	115
	116	Supported global commands
	117	-------------------------
	118	Unrecognized commands are ignored.
	119
6b62b9a3 WD	120	default <label> - the label named here is treated as the default and is
6b62b9a3 WD	121	the first label 'pxe boot' attempts to boot.
06283a64 JH	122
	123	menu title <string> - sets a title for the menu of labels being displayed.
	124
	125	menu include <path> - use tftp to retrieve the pxe file at <path>, which
6b62b9a3 WD	126	is then immediately parsed as if the start of its
	127	contents were the next line in the current file. nesting
	128	of include up to 16 files deep is supported.
06283a64	129
6b62b9a3 WD	130	prompt <flag> - if 1, always prompt the user to enter a label to boot
6b62b9a3 WD	131	from. if 0, only prompt the user if timeout expires.
06283a64 JH	132
06283a64 JH	133	timeout <num> - wait for user input for <num>/10 seconds before
6b62b9a3	134	auto-booting a node.
06283a64	135
6b62b9a3 WD	136	label <name> - begin a label definition. labels continue until
	137	a command not recognized as a label command is seen,
	138	or EOF is reached.
06283a64 JH	139
	140	Supported label commands
	141	------------------------
	142	labels end when a command not recognized as a label command is reached, or EOF.
	143
6b62b9a3 WD	144	menu default - set this label as the default label to boot; this is
	145	the same behavior as the global default command but
	146	specified in a different way
06283a64	147
6b62b9a3	148	kernel <path> - if this label is chosen, use tftp to retrieve the kernel
fce78503 WS	149	(or FIT image) at <path>. it will be stored at the address
	150	indicated in the kernel_addr_r environment variable, and
	151	that address will be passed to bootm to boot this kernel.
2023000a PD	152	For FIT image, The configuration specification can be
	153	appended to the file name, with the format:
	154	<path>#<conf>[#<extra-conf[#...]]
	155	It will passed to bootm with that address.
	156	(see: doc/uImage.FIT/command_syntax_extensions.txt)
	157	It useful for overlay selection in pxe file
	158	(see: doc/uImage.FIT/overlay-fdt-boot.txt)
06283a64	159
69076dff NA	160	fdtoverlays <path> [...] - if this label is chosen, use tftp to retrieve the DT
	161	overlay(s) at <path>. it will be temporarily stored at the
	162	address indicated in the fdtoverlay_addr_r environment variable,
	163	and then applied in the load order to the fdt blob stored at the
	164	address indicated in the fdt_addr_r environment variable.
	165
35821a25 ET	166	devicetree-overlay <path> [...] - if this label is chosen, use tftp to retrieve the DT
	167	overlay(s) at <path>. it will be temporarily stored at the
	168	address indicated in the fdtoverlay_addr_r environment variable,
	169	and then applied in the load order to the fdt blob stored at the
	170	address indicated in the fdt_addr_r environment variable.
	171	Alias for fdtoverlays.
	172
02901469 ZN	173	kaslrseed - set this label to request random number from hwrng as kaslr seed.
02901469 ZN	174
6b62b9a3 WD	175	append <string> - use <string> as the kernel command line when booting this
6b62b9a3 WD	176	label.
06283a64	177
6b62b9a3 WD	178	initrd <path> - if this label is chosen, use tftp to retrieve the initrd
	179	at <path>. it will be stored at the address indicated in
	180	the initrd_addr_r environment variable, and that address
	181	will be passed to bootm.
a5dacef7 PD	182	For FIT image, the initrd can be provided with the same value than
	183	kernel, including configuration:
	184	<path>#<conf>[#<extra-conf[#...]]
	185	In this case, kernel_addr_r is passed to bootm.
06283a64	186
a655938a CK	187	fdt <path> - if this label is chosen, use tftp to retrieve the fdt blob
	188	at <path>. it will be stored at the address indicated in
	189	the fdt_addr_r environment variable, and that address will
	190	be passed to bootm.
a5dacef7 PD	191	For FIT image, the device tree can be provided with the same value
	192	than kernel, including configuration:
	193	<path>#<conf>[#<extra-conf[#...]]
	194	In this case, kernel_addr_r is passed to bootm.
a655938a	195
35821a25 ET	196	devicetree <path> - if this label is chosen, use tftp to retrieve the fdt blob
	197	at <path>. it will be stored at the address indicated in
	198	the fdt_addr_r environment variable, and that address will
	199	be passed to bootm. Alias for fdt.
	200
6015f8f1 SB	201	fdtdir <path> - if this label is chosen, use tftp to retrieve a fdt blob
	202	relative to <path>. If the fdtfile environment variable
	203	is set, <path>/<fdtfile> is retrieved. Otherwise, the
	204	filename is generated from the soc and board environment
	205	variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
	206	If the fdt command is specified, fdtdir is ignored.
	207
06283a64	208	localboot <flag> - Run the command defined by "localcmd" in the environment.
6b62b9a3 WD	209	<flag> is ignored and is only here to match the syntax of
6b62b9a3 WD	210	PXELINUX config files.
06283a64 JH	211
	212	Example
	213	-------
	214	Here's a couple of example files to show how this works.
	215
695c1329	216	------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
06283a64 JH	217	menu title Linux selections
	218
	219	# This is the default label
	220	label install
	221	menu label Default Install Image
	222	kernel kernels/install.bin
	223	append console=ttyAMA0,38400 debug earlyprintk
	224	initrd initrds/uzInitrdDebInstall
	225
	226	# Just another label
	227	label linux-2.6.38
	228	kernel kernels/linux-2.6.38.bin
	229	append root=/dev/sdb1
	230
	231	# The locally installed kernel
	232	label local
	233	menu label Locally installed kernel
	234	append root=/dev/sdb1
	235	localboot 1
	236	-------------------------------------------------------------
	237
	238	------------/tftpboot/pxelinux.cfg/default-------------------
	239	menu include pxelinux.cfg/menus/base.menu
	240	timeout 500
	241
	242	default linux-2.6.38
	243	-------------------------------------------------------------
	244
	245	When a pxe client retrieves and boots the default pxe file,
	246	'pxe boot' will wait for user input for 5 seconds before booting
	247	the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
	248	to be downloaded, and boot with the command line "root=/dev/sdb1"
	249
	250	Differences with PXELINUX
	251	=========================
a187559e BM	252	The biggest difference between U-Boot's pxe and PXELINUX is that since
	253	U-Boot's pxe support is written entirely in C, it can run on any platform
	254	with network support in U-Boot. Here are some other differences between
	255	PXELINUX and U-Boot's pxe support.
06283a64	256
a187559e	257	- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
06283a64 JH	258	in RFC 5071, but could be extended to do so.
06283a64 JH	259
a187559e BM	260	- when U-Boot's pxe fails to boot, it will return control to U-Boot,
a187559e BM	261	allowing another command to run, other U-Boot command, instead of resetting
06283a64 JH	262	the machine like PXELINUX.
06283a64 JH	263
a187559e BM	264	- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
a187559e BM	265	only uses U-Boot.
06283a64	266
a187559e	267	- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
06283a64	268	does, only a simple text based menu using the commands described in
6b62b9a3	269	this README. With PXELINUX, it's possible to have a graphical boot
a187559e	270	menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
06283a64 JH	271	a more robust menuing system like that of PXELINUX's.
06283a64 JH	272
a187559e BM	273	- U-Boot's pxe expects U-Boot uimg's as kernels. Anything that would work
a187559e BM	274	with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
06283a64	275
a187559e	276	- U-Boot's pxe only recognizes a single file on the initrd command line. It
06283a64 JH	277	could be extended to support multiple.
06283a64 JH	278
a187559e	279	- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
06283a64 JH	280	disk boot - it will do whatever is defined in the 'localcmd' env
	281	variable. And since it doesn't support a full UNDI/PXE stack, the
	282	type field is ignored.
	283
a187559e	284	- the interactive prompt in U-Boot's pxe only allows you to choose a label
06283a64	285	from the menu. If you want to boot something not listed, you can ctrl+c
a187559e	286	out of 'pxe boot' and use existing U-Boot commands to accomplish it.