1/* 2 * Copyright 2010-2011 Calxeda, Inc. 3 * 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) 7 * any later version. 8 * 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 12 * more details. 13 * 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/>. 16 */ 17 18The 'pxe' commands provide a near subset of the functionality provided by 19the PXELINUX boot loader. This allows U-boot based systems to be controlled 20remotely using the same PXE based techniques that many non U-boot based servers 21use. 22 23Commands 24======== 25 26pxe get 27------- 28 syntax: pxe get 29 30 follows PXELINUX's rules for retrieving configuration files from a tftp 31 server, and supports a subset of PXELINUX's config file syntax. 32 33 Environment 34 ----------- 35 'pxe get' requires two environment variables to be set: 36 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 41 long. 42 43 bootfile,serverip - these two are typically set in the DHCP response 44 handler, and correspond to fields in the DHCP response. 45 46 'pxe get' optionally supports these two environment variables being set: 47 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 50 MAC address. 51 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. 55 56 File Paths 57 ---------- 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: 62 63 http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux 64 65pxe boot 66-------- 67 syntax: pxe boot [pxefile_addr_r] 68 69 Interprets a pxe file stored in memory. 70 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. 73 74 Environment 75 ----------- 76 There are some environment variables that may need to be set, depending 77 on conditions. 78 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. 82 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. 87 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. 90 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. 95 96 fdt_addr - the location of a fdt blob. If this is set, it will be passed 97 to bootm when booting a kernel. 98 99pxe file format 100=============== 101The pxe file format is nearly a subset of the PXELINUX file format; see 102http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line 103commands - global commands, and commands specific to labels. Lines begining 104with # are treated as comments. White space between and at the beginning of 105lines is ignored. 106 107The size of pxe files and the number of labels is only limited by the amount 108of RAM available to U-boot. Memory for labels is dynamically allocated as 109they're parsed, and memory for pxe files is statically allocated, and its 110location is given by the pxefile_addr_r environment variable. The pxe code is 111not aware of the size of the pxefile memory and will outgrow it if pxe files 112are too large. 113 114Supported global commands 115------------------------- 116Unrecognized commands are ignored. 117 118default <label> - the label named here is treated as the default and is 119 the first label 'pxe boot' attempts to boot. 120 121menu title <string> - sets a title for the menu of labels being displayed. 122 123menu include <path> - use tftp to retrieve the pxe file at <path>, which 124 is then immediately parsed as if the start of its 125 contents were the next line in the current file. nesting 126 of include up to 16 files deep is supported. 127 128prompt <flag> - if 1, always prompt the user to enter a label to boot 129 from. if 0, only prompt the user if timeout expires. 130 131timeout <num> - wait for user input for <num>/10 seconds before 132 auto-booting a node. 133 134label <name> - begin a label definition. labels continue until 135 a command not recognized as a label command is seen, 136 or EOF is reached. 137 138Supported label commands 139------------------------ 140labels end when a command not recognized as a label command is reached, or EOF. 141 142menu default - set this label as the default label to boot; this is 143 the same behavior as the global default command but 144 specified in a different way 145 146kernel <path> - if this label is chosen, use tftp to retrieve the kernel 147 at <path>. it will be stored at the address indicated in 148 the kernel_addr_r environment variable, and that address 149 will be passed to bootm to boot this kernel. 150 151append <string> - use <string> as the kernel command line when booting this 152 label. 153 154initrd <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. 158 159localboot <flag> - Run the command defined by "localcmd" in the environment. 160 <flag> is ignored and is only here to match the syntax of 161 PXELINUX config files. 162 163Example 164------- 165Here's a couple of example files to show how this works. 166 167------------/tftpboot/pxelinux.cfg/menus/linux.list---------- 168menu title Linux selections 169 170# This is the default label 171label install 172 menu label Default Install Image 173 kernel kernels/install.bin 174 append console=ttyAMA0,38400 debug earlyprintk 175 initrd initrds/uzInitrdDebInstall 176 177# Just another label 178label linux-2.6.38 179 kernel kernels/linux-2.6.38.bin 180 append root=/dev/sdb1 181 182# The locally installed kernel 183label local 184 menu label Locally installed kernel 185 append root=/dev/sdb1 186 localboot 1 187------------------------------------------------------------- 188 189------------/tftpboot/pxelinux.cfg/default------------------- 190menu include pxelinux.cfg/menus/base.menu 191timeout 500 192 193default linux-2.6.38 194------------------------------------------------------------- 195 196When a pxe client retrieves and boots the default pxe file, 197'pxe boot' will wait for user input for 5 seconds before booting 198the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin 199to be downloaded, and boot with the command line "root=/dev/sdb1" 200 201Differences with PXELINUX 202========================= 203The biggest difference between U-boot's pxe and PXELINUX is that since 204U-boot's pxe support is written entirely in C, it can run on any platform 205with network support in U-boot. Here are some other differences between 206PXELINUX and U-boot's pxe support. 207 208- U-boot's pxe does not support the PXELINUX DHCP option codes specified 209 in RFC 5071, but could be extended to do so. 210 211- when U-boot's pxe fails to boot, it will return control to U-boot, 212 allowing another command to run, other U-boot command, instead of resetting 213 the machine like PXELINUX. 214 215- U-boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it 216 only uses U-boot. 217 218- U-boot's pxe doesn't provide the full menu implementation that PXELINUX 219 does, only a simple text based menu using the commands described in 220 this README. With PXELINUX, it's possible to have a graphical boot 221 menu, submenus, passwords, etc. U-boot's pxe could be extended to support 222 a more robust menuing system like that of PXELINUX's. 223 224- U-boot's pxe expects U-boot uimg's as kernels. Anything that would work 225 with the 'bootm' command in U-boot could work with the 'pxe boot' command. 226 227- U-boot's pxe doesn't recognize initrd options in the append command - you 228 must specify initrd files using the initrd command. 229 230- U-boot's pxe only recognizes a single file on the initrd command line. It 231 could be extended to support multiple. 232 233- in U-boot's pxe, the localboot command doesn't necessarily cause a local 234 disk boot - it will do whatever is defined in the 'localcmd' env 235 variable. And since it doesn't support a full UNDI/PXE stack, the 236 type field is ignored. 237 238- the interactive prompt in U-boot's pxe only allows you to choose a label 239 from the menu. If you want to boot something not listed, you can ctrl+c 240 out of 'pxe boot' and use existing U-boot commands to accomplish it. 241