| /* |
| * Copyright 2010-2011 Calxeda, Inc. |
| * |
| * This program is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License as published by the Free |
| * Software Foundation; either version 2 of the License, or (at your option) |
| * any later version. |
| * |
| * This program is distributed in the hope it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| * more details. |
| * |
| * You should have received a copy of the GNU General Public License along with |
| * this program. If not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| 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 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. |
| |
| 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 |
| 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. |
| |
| 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. |
| |
| 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/linux.list---------- |
| 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. |
