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_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. 100 101 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. 103 104pxe file format 105=============== 106The pxe file format is nearly a subset of the PXELINUX file format; see 107http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line 108commands - global commands, and commands specific to labels. Lines begining 109with # are treated as comments. White space between and at the beginning of 110lines is ignored. 111 112The size of pxe files and the number of labels is only limited by the amount 113of RAM available to U-boot. Memory for labels is dynamically allocated as 114they're parsed, and memory for pxe files is statically allocated, and its 115location is given by the pxefile_addr_r environment variable. The pxe code is 116not aware of the size of the pxefile memory and will outgrow it if pxe files 117are too large. 118 119Supported global commands 120------------------------- 121Unrecognized commands are ignored. 122 123default <label> - the label named here is treated as the default and is 124 the first label 'pxe boot' attempts to boot. 125 126menu title <string> - sets a title for the menu of labels being displayed. 127 128menu 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. 132 133prompt <flag> - if 1, always prompt the user to enter a label to boot 134 from. if 0, only prompt the user if timeout expires. 135 136timeout <num> - wait for user input for <num>/10 seconds before 137 auto-booting a node. 138 139label <name> - begin a label definition. labels continue until 140 a command not recognized as a label command is seen, 141 or EOF is reached. 142 143Supported label commands 144------------------------ 145labels end when a command not recognized as a label command is reached, or EOF. 146 147menu 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 150 151kernel <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. 155 156append <string> - use <string> as the kernel command line when booting this 157 label. 158 159initrd <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. 163 164fdt <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 167 be passed to bootm. 168 169localboot <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. 172 173Example 174------- 175Here's a couple of example files to show how this works. 176 177------------/tftpboot/pxelinux.cfg/menus/linux.list---------- 178menu title Linux selections 179 180# This is the default label 181label install 182 menu label Default Install Image 183 kernel kernels/install.bin 184 append console=ttyAMA0,38400 debug earlyprintk 185 initrd initrds/uzInitrdDebInstall 186 187# Just another label 188label linux-2.6.38 189 kernel kernels/linux-2.6.38.bin 190 append root=/dev/sdb1 191 192# The locally installed kernel 193label local 194 menu label Locally installed kernel 195 append root=/dev/sdb1 196 localboot 1 197------------------------------------------------------------- 198 199------------/tftpboot/pxelinux.cfg/default------------------- 200menu include pxelinux.cfg/menus/base.menu 201timeout 500 202 203default linux-2.6.38 204------------------------------------------------------------- 205 206When a pxe client retrieves and boots the default pxe file, 207'pxe boot' will wait for user input for 5 seconds before booting 208the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin 209to be downloaded, and boot with the command line "root=/dev/sdb1" 210 211Differences with PXELINUX 212========================= 213The biggest difference between U-boot's pxe and PXELINUX is that since 214U-boot's pxe support is written entirely in C, it can run on any platform 215with network support in U-boot. Here are some other differences between 216PXELINUX and U-boot's pxe support. 217 218- U-boot's pxe does not support the PXELINUX DHCP option codes specified 219 in RFC 5071, but could be extended to do so. 220 221- 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. 224 225- U-boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it 226 only uses U-boot. 227 228- 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. 233 234- 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. 236 237- U-boot's pxe only recognizes a single file on the initrd command line. It 238 could be extended to support multiple. 239 240- 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. 244 245- 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. 248