2 * Copyright 2010-2011 Calxeda, Inc.
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License as published by the Free
6 * Software Foundation; either version 2 of the License, or (at your option)
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 * You should have received a copy of the GNU General Public License along with
15 * this program. If not, see <http://www.gnu.org/licenses/>.
18 The 'pxe' commands provide a near subset of the functionality provided by
19 the PXELINUX boot loader. This allows U-boot based systems to be controlled
20 remotely using the same PXE based techniques that many non U-boot based servers
30 follows PXELINUX's rules for retrieving configuration files from a tftp
31 server, and supports a subset of PXELINUX's config file syntax.
35 'pxe get' requires two environment variables to be set:
37 pxefile_addr_r - should be set to a location in RAM large enough to hold
38 pxe files while they're being processed. Up to 16 config files may be
39 held in memory at once. The exact number and size of the files varies with
40 how the system is being used. A typical config file is a few hundred bytes
43 bootfile,serverip - these two are typically set in the DHCP response
44 handler, and correspond to fields in the DHCP response.
46 'pxe get' optionally supports these two environment variables being set:
48 ethaddr - this is the standard MAC address for the ethernet adapter in use.
49 'pxe get' uses it to look for a configuration file specific to a system's
52 pxeuuid - this is a UUID in standard form using lower case hexadecimal
53 digits, for example, 550e8400-e29b-41d4-a716-446655440000. 'pxe get' uses
54 it to look for a configuration file based on the system's UUID.
58 'pxe get' repeatedly tries to download config files until it either
59 successfully downloads one or runs out of paths to try. The order and
60 contents of paths it tries mirrors exactly that of PXELINUX - you can
61 read in more detail about it at:
63 http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux
67 syntax: pxe boot [pxefile_addr_r]
69 Interprets a pxe file stored in memory.
71 pxefile_addr_r is an optional argument giving the location of the pxe file.
72 The file must be terminated with a NUL byte.
76 There are some environment variables that may need to be set, depending
79 pxefile_addr_r - if the optional argument pxefile_addr_r is not supplied,
80 an environment variable named pxefile_addr_r must be supplied. This is
81 typically the same value as is used for the 'pxe get' command.
83 bootfile - typically set in the DHCP response handler based on the
84 same field in the DHCP respone, this path is used to generate the base
85 directory that all other paths to files retrieved by 'pxe boot' will use.
86 If no bootfile is specified, paths used in pxe files will be used as is.
88 serverip - typically set in the DHCP response handler, this is the IP
89 address of the tftp server from which other files will be retrieved.
91 kernel_addr_r, initrd_addr_r - locations in RAM at which 'pxe boot' will
92 store the kernel and initrd it retrieves from tftp. These locations will
93 be passed to the bootm command to boot the kernel. These environment
94 variables are required to be set.
96 fdt_addr_r - location in RAM at which 'pxe boot' will store the fdt blob it
97 retrieves from tftp. The retrieval is possible if 'fdt' label is defined in
98 pxe file and 'fdt_addr_r' is set. If retrieval is possible, 'fdt_addr_r'
99 will be passed to bootm command to boot the kernel.
101 fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
102 command if it is set and 'fdt_addr_r' is not passed to bootm command.
106 The pxe file format is nearly a subset of the PXELINUX file format; see
107 http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
108 commands - global commands, and commands specific to labels. Lines begining
109 with # are treated as comments. White space between and at the beginning of
112 The size of pxe files and the number of labels is only limited by the amount
113 of RAM available to U-boot. Memory for labels is dynamically allocated as
114 they're parsed, and memory for pxe files is statically allocated, and its
115 location is given by the pxefile_addr_r environment variable. The pxe code is
116 not aware of the size of the pxefile memory and will outgrow it if pxe files
119 Supported global commands
120 -------------------------
121 Unrecognized commands are ignored.
123 default <label> - the label named here is treated as the default and is
124 the first label 'pxe boot' attempts to boot.
126 menu title <string> - sets a title for the menu of labels being displayed.
128 menu include <path> - use tftp to retrieve the pxe file at <path>, which
129 is then immediately parsed as if the start of its
130 contents were the next line in the current file. nesting
131 of include up to 16 files deep is supported.
133 prompt <flag> - if 1, always prompt the user to enter a label to boot
134 from. if 0, only prompt the user if timeout expires.
136 timeout <num> - wait for user input for <num>/10 seconds before
139 label <name> - begin a label definition. labels continue until
140 a command not recognized as a label command is seen,
143 Supported label commands
144 ------------------------
145 labels end when a command not recognized as a label command is reached, or EOF.
147 menu default - set this label as the default label to boot; this is
148 the same behavior as the global default command but
149 specified in a different way
151 kernel <path> - if this label is chosen, use tftp to retrieve the kernel
152 at <path>. it will be stored at the address indicated in
153 the kernel_addr_r environment variable, and that address
154 will be passed to bootm to boot this kernel.
156 append <string> - use <string> as the kernel command line when booting this
159 initrd <path> - if this label is chosen, use tftp to retrieve the initrd
160 at <path>. it will be stored at the address indicated in
161 the initrd_addr_r environment variable, and that address
162 will be passed to bootm.
164 fdt <path> - if this label is chosen, use tftp to retrieve the fdt blob
165 at <path>. it will be stored at the address indicated in
166 the fdt_addr_r environment variable, and that address will
169 localboot <flag> - Run the command defined by "localcmd" in the environment.
170 <flag> is ignored and is only here to match the syntax of
171 PXELINUX config files.
175 Here's a couple of example files to show how this works.
177 ------------/tftpboot/pxelinux.cfg/menus/linux.list----------
178 menu title Linux selections
180 # This is the default label
182 menu label Default Install Image
183 kernel kernels/install.bin
184 append console=ttyAMA0,38400 debug earlyprintk
185 initrd initrds/uzInitrdDebInstall
189 kernel kernels/linux-2.6.38.bin
190 append root=/dev/sdb1
192 # The locally installed kernel
194 menu label Locally installed kernel
195 append root=/dev/sdb1
197 -------------------------------------------------------------
199 ------------/tftpboot/pxelinux.cfg/default-------------------
200 menu include pxelinux.cfg/menus/base.menu
204 -------------------------------------------------------------
206 When a pxe client retrieves and boots the default pxe file,
207 'pxe boot' will wait for user input for 5 seconds before booting
208 the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
209 to be downloaded, and boot with the command line "root=/dev/sdb1"
211 Differences with PXELINUX
212 =========================
213 The biggest difference between U-boot's pxe and PXELINUX is that since
214 U-boot's pxe support is written entirely in C, it can run on any platform
215 with network support in U-boot. Here are some other differences between
216 PXELINUX and U-boot's pxe support.
218 - U-boot's pxe does not support the PXELINUX DHCP option codes specified
219 in RFC 5071, but could be extended to do so.
221 - when U-boot's pxe fails to boot, it will return control to U-boot,
222 allowing another command to run, other U-boot command, instead of resetting
223 the machine like PXELINUX.
225 - U-boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
228 - U-boot's pxe doesn't provide the full menu implementation that PXELINUX
229 does, only a simple text based menu using the commands described in
230 this README. With PXELINUX, it's possible to have a graphical boot
231 menu, submenus, passwords, etc. U-boot's pxe could be extended to support
232 a more robust menuing system like that of PXELINUX's.
234 - U-boot's pxe expects U-boot uimg's as kernels. Anything that would work
235 with the 'bootm' command in U-boot could work with the 'pxe boot' command.
237 - U-boot's pxe only recognizes a single file on the initrd command line. It
238 could be extended to support multiple.
240 - in U-boot's pxe, the localboot command doesn't necessarily cause a local
241 disk boot - it will do whatever is defined in the 'localcmd' env
242 variable. And since it doesn't support a full UNDI/PXE stack, the
243 type field is ignored.
245 - the interactive prompt in U-boot's pxe only allows you to choose a label
246 from the menu. If you want to boot something not listed, you can ctrl+c
247 out of 'pxe boot' and use existing U-boot commands to accomplish it.