PXELINUX Version 1.49 A bootloader for Linux using the PXE network booting protocol Copyright (C) 1994-2000 H. Peter Anvin This program is provided under the terms of the GNU General Public License, version 2 or, at your option, any later version. There is no warranty, neither expressed nor implied, to the function of this program. Please see the included file COPYING for details. ---------------------------------------------------------------------- PXELINUX is a SYSLINUX derivative, for booting Linux off a network server, using a network ROM conforming to the Intel PXE (Pre-Execution Environment) specification. PXELINUX is *not* a program that is intended to be flashed or burned into a PROM on the network card; if you want that, check out NILO (http://www.nilo.org/). NILO can also be used to create a PXE-compliant boot PROM for most network cards which have drivers for Linux or FreeBSD. ++++ HOW TO CONFIGURE PXELINUX ++++ PXELINUX operates in many ways like SYSLINUX. If you are not familiar with SYSLINUX, read syslinux.doc first, since this documentation only explains the differences. On the TFTP server, create the directory "/tftpboot", and copy the following files to it: pxelinux.bin - from the SYSLINUX distribution any kernel or initrd images you want to boot Finally, create the directory "/tftpboot/pxelinux.cfg". The configuration file (equivalent of syslinux.cfg) will live in this directory. Because more than one system may be booted from the same server, the configuration file name depends on the IP address of the booting machine. PXELINUX will search for its config file on the boot server in the following way: First, it will search for the config file using its own IP address in upper case hexadecimal, e.g. 192.0.2.91 -> C000025B. If that file is not found, it will remove one hex digit and try again. Ultimately, it will try looking for a file named "default" (in lower case). As an example, for 192.0.2.91, it will try C000025B, C000025, C00002, C0000, C000, C00, C0, C, and default, in that order. It should be noted that all filename references are relative to the directory pxelinux.bin lives in (usually /tftpboot). PXELINUX generally requires that filenames are 31 characters or shorter in length. PXELINUX does not support MTFTP, and I have no immediate plans of doing so. It is of course possible to use MTFTP for the initial boot, if you have such a setup. MTFTP server setup is beyond the scope of this document. ++++ SOME NOTES ON THE TFTP SERVER ++++ PXELINUX currently requires that the boot server has a TFTP server which supports the "tsize" TFTP option (RFC 1784/RFC 2349). The "tftp-hpa" TFTP server, which support options, is available at: http://www.kernel.org/pub/software/network/tftp/ ftp://www.kernel.org/pub/software/network/tftp/ ... and on any kernel.org mirror (see http://www.kernel.org/mirrors/). Unfortunately, the Intel LANDesk Service Agent II prior to version 0.99h (PXE PDK V2.4) seems to have a rather serious bug: it requests the TFTP "blksize" option, but will be mortally confused if this option is actually accepted by the server! There are three possible workarounds for this bug: 1. Use a TFTP server with doesn't support "blksize". Unfortunately, PXELINUX requires the "tsize" option to be supported, and it is very unusual for TFTP servers to implement one and not the other. The "tftp-hpa" TFTP server (see above) therefore can be configured to disable individual options with a command-line option (-r ). In this case, use "-r blksize". 2. Use MTFTP for the initial bootstrap. You need an MTFTP server with the appropriate DHCP setup to do this. 3. Use appropriate DHCP options that the client will attempt MTFTP before trying conventional TFTP. It seems that the client will not request the "blksize" option if it has tried MTFTP and failed. These DHCP options are beyond the scope of this document. ++++ SETTING UP THE DHCP SERVER ++++ The PXE protocol uses a very complex set of extensions to DHCP or BOOTP. ISC dhcp 3.0, currently in beta, appears to have enough smarts to support at least most of the full protocol. However, I believe I have found a magic cookie set of options which is adequate to make all or most existing PXE client boot. Using ISC dhcp 2.0 dhcpd.conf syntax: allow booting; allow bootp; filename "/tftpboot/pxelinux.bin" ; option dhcp-class-identifier "PXEClient"; option vendor-encapsulated-options 09:0f:80:00:0c:4e:65:74:77:6f:72:6b:20:62:6f:6f:74:0a:07:00:50:72:6f:6d:70:74:06:01:02:08:03:80:00:00:47:04:80:00:00:00:ff; next-server ; # server-identifier ; # Illegal! See below option domain-name ""; option subnet-mask ; option broadcast-address ; option domain-name-servers ; option routers ; # Skip everything below if you want to use dynamic IP # address assignment host { hardware ethernet ; fixed-address ; } Note that if your particular TFTP daemon runs under chroot (tftp-hpa will do this if you specify the -s (secure) option; this is recommended), you most likely should not include the /tftpboot prefix. If the DHCP and TFTP servers are not on the same machine, you are supposed to set up a DHCP server on port 4011 on the TFTP server; this is the "PXE boot server", which uses the DHCP protocol. If this is not possible, you can try adding the directive "server-identifier ;" Unfortunately this is a violation of DHCP protocol, but some PXE implementations do not accept the next-server directive without it or the "boot server". I have successfully booted an Intel N440BX ("Nightshade") motherboard with onboard Ethernet and "Intel LANDesk(R) Service Agent II version 0.99c" (derived from the Intel PXE PDK V2.0) and the Intel PRO/100+ Management Adapter "Boot agent 2.6 (build 071)" (derived from the Intel PXE PDK V3.0 bld 071) using the configuration above and ISC dhcpd 2.0. ++++ SOME NOTES ++++ If the boot fails, PXELINUX (unlike SYSLINUX) will not wait forever; rather, if it has not received any input for approximately five minutes after displaying an error message, it will reset the machine. This allows an unattended machine to recover in case it had bad enough luck of trying to boot at the same time the TFTP server goes down. ++++ PXELINUX IS STILL BETA ++++ PXELINUX is still very much beta; however, I'd be interested in hearing about any experiences you might have with it, good or bad. If you have any comments, please use the SYSLINUX mailing list mentioned at the end of syslinux.doc. Thanks! Currently known problems: + Requires a TFTP server which supports the "tsize" option. + The error recovery routine doesn't work quite right. For right now, it just does a hard reset - seems good enough. + There may be funnies with memory management. The PXE spec has no decent way of telling it to free up all memory and unchain any interrupts; it allows the base stack to be unloaded, but not the UNDI driver. + There seems to be a problem with sending ACK "storms"; a number of ACK packets fired off without the proper delay in between. I suspect this is a PXE firmware problem, rather than a PXELINUX problem. + We should probably call the UDP receive function in the keyboard entry loop, so that we answer ARP requests. + Boot sectors don't work yet... they probably need auxilliary information (such as device) to work at all. * No way to chain-load onto a hard disk.