PXE network booting
This page described the installation of a Linux OS on a computer by means of PXE (Preboot Execution Environment) booting. See also pages on:
PXE_and_UEFI network booting.
SYSLINUX and PXELINUX
PXE network booting from Linux servers uses the SYSLINUX and PXELINUX utilities (see also this Wikipedia article). Read the documentation on these pages to get an understanding of the process. The SYSLINUX source code has additional very useful documentation which we have copied here: syslinux.doc and pxelinux.doc.
There is a SYSLINUX mailing list as well as a SYSLINUX Wiki.
SYSLINUX documentation
Boot process summary
When a client computer performs a PXE network boot, the Linux DHCP server assigns the client an IP-address
and further information including a TFTP-server address (DHCP next-server option)
and a boot image file name pxelinux.0 (DHCP filename option).
The client retrieves the file pxelinux.0 from the TFTP server and executes it.
The pxelinux.0 PXELINUX boot image then attempts to download configurations files from the TFTP server
in the boot process explained here.
To summarize: The PXE/network client will use TFTP to download a PXELINUX configuration file
from the server’s /tftpboot/pxelinux.cfg/ directory
whose name is usually either:
the client’s hexadecimally encoded IP-address (such as
0A018219), orthe file named
default.
With newer versions of SYSLINUX it is also possible to PXE-boot into the SYSLINUX menu systems where many booting options can be configured. This is a very flexible way to boot, for example, diskette images with BIOS upgrades, hardware testers, or Kickstart installation, etc.
Installing the SYSLINUX tools
Although your Linux machine may already have some of the SYSLINUX tools installed, it is recommended that you get the latest version of SYSLINUX.
Unpack the tar-ball and copy the following SYSLINUX files to the /tftpboot directory on the DHCP/TFTP server:
tar xzvf syslinux-4.02.tar.gz
cd syslinux-4.02
cp core/pxelinux.0 memdisk/memdisk com32/modules/chain.c32 com32/menu/menu.c32 /tftpboot/
(version 4.02 is used in this example). Additional com32/*/*.c32 modules might be needed if further features from SYSLINUX will be used.
For the older SYSLINUX version 3.x the locations of files differ a bit, so do:
tar xzvf syslinux-3.51.tar.gz
cd syslinux-3.51
cp pxelinux.0 memdisk/memdisk com32/modules/*.c32 /tftpboot/
If for some reason you must rebuild SYSLINUX, first verify that you have the nasm package installed:
rpm -q nasm
Then build SYSLINUX in the top-level directory by doing simply make.
See also the file distrib.doc for further details.
The default file
You must also create a default PXE boot file /tftpboot/pxelinux.cfg/default instructing the
node how to boot in case there is no hexadecimally encoded IP-address file.
Probably the most sensible default boot method is local hard disk which is configured as follows:
We assume that you have installed the SYSLINUX tools as shown above, in particular the chain.c32 tool.
Then create the file named default containing these lines:
default harddisk
label harddisk
kernel chain.c32
append hd0
For comparison, in many places you will find the following recipe for the default file:
default harddisk
label harddisk
localboot 0
This recipe can be error-prone and actually means boot from the next device in the BIOS boot order, rather than booting from the hard disk as you would be led to believe. For more information read this article from the SYSLINUX mailing list (look at the bottom of the article).
Etherboot/gPXE
Something to consider for the future is the Etherboot/gPXE project which permits a larger set of boot media, includign also HTTP-servers. For PXE-booting into gPXE see PXE chainloading.
Linux and Windows deployment (WDS)
A Microsoft Windows Deployment Service WDS takes over PXE booting of any PXE clients it has configured, thus the clients will ignore the Linux PXE boot server.
For a solution, see Linux and Windows deployment:
This covers the setup and deployment of a PXE boot solution consisting of 2 pxe servers and one dhcp server. The 2 PXE servers are linux and windows - the former running pxelinux and tftp and the latter one running WDS (Windows Deployment Services), with a linux server providing DHCP services.
See also Peaceful Coexistence: WDS and Linux PXE Servers:
As it turns out, thanks to the lesser-known pxechain utility, it is possible to seamlessly jump from one PXE host to another. With a few tweaks to your WDS server, you can continue to use it for Windows OS installs and bounce over to a Linux host for Linux, ESXi, or rescue-CD purposes.
SYSLINUX Menu systems
With newer versions of SYSLINUX it is possible to PXE-boot into the SYSLINUX menu systems where many booting options can be configured. This is a very flexible way to boot, for example, diskette images with BIOS upgrades, hardware testers, or Kickstart installation, etc.
Please consult the README.menu from the SYSLINUX source.
One must first install SYSLINUX files to /tftpboot on the DHCP/TFTP server as shown in Installing the SYSLINUX tools.
Secondly, for each client machine that should use the SYSLINUX menu systems a hexadecimally encoded IP-address file
must be created in /tftpboot/pxelinux.cfg/, pointing to the menu configuration file.
This can conveniently be done with the pxeconfig command discussed below.
An example default.menu SYSLINUX menu file in /tftpboot/pxelinux.cfg/ is:
DEFAULT menu.c32
PROMPT 0
MENU TITLE Menu from TFTP server
label AlmaLinux8.8 minimal-x86_64
menu label Clean AlmaLinux-8.8-x86_64, minimal install
kernel AlmaLinux-8.8-x86_64/vmlinuz
append load_ramdisk=1 initrd=AlmaLinux-8.8-x86_64/initrd.img network inst.ks=nfs:<some-IP-address>:/u/kickstart/ks-almalinux-8.8-minimal-x86_64.cfg vga=792
label harddisk
menu label Boot from local harddisk
kernel chain.c32
append hd0
This configuration will display a menu with 4 items, each performing a different task
as described in the menu label lines.
Commandline key strokes
The command line prompt supports the following keystrokes (see syslinux.doc):
<Enter> boot specified command line
<BackSpace> erase one character
<Ctrl-U> erase the whole line
<Ctrl-V> display the current SYSLINUX version
<Ctrl-W> erase one word
<Ctrl-X> force text mode
<F1>..<F10> help screens (if configured)
<Ctrl-F><digit> equivalent to F1..F10
<Ctrl-C> interrupt boot in progress
<Esc> interrupt boot in progress