关于PXELINUX的一些重要描述摘录

以下资源都来自官方文档，原文摘录

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 Etherboot. Etherboot 5.4 or later can also be used to create a PXE-compliant boot PROM for many network cards.

HOW TO CONFIGURE PXELINUX

PXELINUX operates in many ways like SYSLINUX. If you are not familiar with SYSLINUX, read syslinux.txt first, since this documentation only explains the differences.

On the TFTP server, create the directory "/tftpboot", and copy the following files to it:

pxelinux.0 - 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 -- see syslinux.txt for the options here) 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 the client UUID, if one is provided by the PXE stack (note, some BIOSes don't have a valid UUID, and you might end up with something like all 1's.) This is in the standard UUID format using lower case hexadecimal digits, e.g. b8945908-d6a6-41a9-611d-74a6ab80b83d.

Next, it will search for the config file using the hardware type (using its ARP type code) and address, all in lower case hexadecimal with dash separators; for example, for an Ethernet (ARP type 1) with address 88:99:AA:BB:CC:DD it would search for the filename 01-88-99-aa-bb-cc-dd.

Next, it will search for the config file using its own IP address in upper case hexadecimal, e.g. 192.0.2.91 -> C000025B (you can use the included progam "gethostip" to compute the hexadecimal IP address for any host.)

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, if the boot file name is /mybootdir/pxelinux.0, the UUID is b8945908-d6a6-41a9-611d-74a6ab80b83d, the Ethernet MAC address is 88:99:AA:BB:CC:DD and the IP address 192.0.2.91, it will try:

	/mybootdir/pxelinux.cfg/b8945908-d6a6-41a9-611d-74a6ab80b83d
	/mybootdir/pxelinux.cfg/01-88-99-aa-bb-cc-dd
	/mybootdir/pxelinux.cfg/C000025B
	/mybootdir/pxelinux.cfg/C000025
	/mybootdir/pxelinux.cfg/C00002
	/mybootdir/pxelinux.cfg/C0000
	/mybootdir/pxelinux.cfg/C000
	/mybootdir/pxelinux.cfg/C00
	/mybootdir/pxelinux.cfg/C0
	/mybootdir/pxelinux.cfg/C
	/mybootdir/pxelinux.cfg/default

... in that order.

Note that all filename references are relative to the directory pxelinux.0 lives in.

Starting in release 3.20, PXELINUX will no longer apply a built-in default if it cannot find any configuration file at all; instead it will reboot after the timeout interval has expired. This keeps a machine from getting stuck indefinitely due to a boot server failure.

 

SETTING UP THE TFTP SERVER

PXELINUX currently requires that the boot server has a TFTP server which supports the "tsize" TFTP option (RFC 1784/RFC 2349). There are both TFTP server,”atftp”and "tftp-hpa" ，which support options.

"tftp-hpa" 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/).

atftp is  by Jean-Pierre Lefebvre:

ftp://ftp.mamalinux.com/pub/atftp/

 

If your boot server is running Windows (and you can't fix that), try tftpd32 by Philippe Jounin (you need version 2.11 or later; previous versions had a bug which made it incompatible with PXELINUX)

SETTING UP THE DHCP SERVER

A sample DHCP setup, using the "conventional TFTP" configuration, would look something like the following, using ISC dhcp 2.0 dhcpd.conf syntax:

allow booting;

allow bootp;

# Standard configuration directives...

option domain-name "<domain name>";

option subnet-mask <subnet mask>;

option broadcast-address <broadcast address>;

option domain-name-servers <dns servers>;

option routers <default router>;

# Group the PXE bootable hosts together

group {

    # PXE-specific configuration directives...

    next-server <TFTP server address>;

    filename "/tftpboot/pxelinux.0";

    # You need an entry like this for every host

    # unless you're using dynamic addresses

        host <hostname> {

            hardware ethernet <ethernet address>;

        fixed-address <hostname>;

    }

}

 

Note that if your particular TFTP daemon runs under chroot(CHROOT就是Change Root，也就是改变程序执行时所参考的根目录位置.tftp-hpa will do this if you specify the -s (secure) option; this is highly recommended), you almost certainly should not include the /tftpboot prefix in the filename statement.

If this does not work for your configuration（如果上述配置无法正常工作）, you probably should set up a "PXE boot server" on port 4011 of your TFTP server; a free PXE boot server is available at:

http://www.kano.org.uk/projects/pxe/

With such a boot server defined, your DHCP configuration should look the same except for an "option dhcp-class-identifier" ("option vendor-class-identifier" if you are using DHCP 3.0):

allow booting;
allow bootp;

# Standard configuration directives...

option domain-name "<domain name>";
option subnet-mask <subnet mask>;
option broadcast-address <broadcast address>;
option domain-name-servers <dns servers>;
option routers <default router>;

# Group the PXE bootable hosts together
group {
	# PXE-specific configuration directives...
        option dhcp-class-identifier "PXEClient";
	next-server <pxe boot server address>;

	# You need an entry like this for every host
	# unless you're using dynamic addresses
        host <hostname> {
	        hardware ethernet <ethernet address>;
		fixed-address <hostname>;
	}
}

Here, the boot file name is obtained from the PXE server. （在这种配置中不用指定引导文件）

 

If the "conventional TFTP" configuration doesn't work on your clients, and setting up a PXE boot server is not an option（如果上述两种配置都无法正常工作）, you can attempt the following configuration. It has been known to boot some configurations correctly; however, there are no guarantees:

allow booting;
allow bootp;

# Standard configuration directives...

option domain-name "<domain name>";
option subnet-mask <subnet mask>;
option broadcast-address <broadcast address>;
option domain-name-servers <dns servers>;
option routers <default router>;

# Group the PXE bootable hosts together
group {
	# PXE-specific configuration directives...
        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 <TFTP server>;
	filename "/tftpboot/pxelinux.0";

	# You need an entry like this for every host
	# unless you're using dynamic addresses
        host <hostname> {
	        hardware ethernet <ethernet address>;
		fixed-address <hostname>;
	}
}

Note that this will not boot some clients that will boot with the "conventional TFTP" configuration; Intel Boot Client 3.0 and later are known to fall into this category.