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opsi manual opsi version 4.0.2
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DHCPREQUEST is the response of the client to the server if the IP address is accepted. (This is not an obsolete step
as there could be more than one server in the network.)
The server sends a DHCPACK to acknowledge the request. The information is sent to the client again.
You can watch this process on the display, for the PXE-BOOTPROM displays some firmware information and its
CLIENT MAC ADDR. The rotating pipe-symbol is displayed during the request. When an offer was made it is
replaced by an \ and you get the transmitted information (CLIENT IP, MASK, DHCP IP, GATEWAY IP). A short
while later you should get a response like this: My IP ADDRESS SEEMS TO BE . . . . . . .
This process makes the PC a regular, fully configured member of the network. The next step is to load the boot file
(boot image) given in the configuration information.
9.2.4 Loading pxelinux
The boot image is loaded via trivial file transfer protocol (tftp). The displayed message is „LOADING“. tftp is a
rather old and simple protocol to transfer files without authentication. In fact, all data available via tftp is available
to everyone in the network. Therefore the tftp access is limited to one directory, which is usually /tftpboot. This
directory is specified in inetd (internet daemon, /etc/inetd.conf), which will start the tftp daemon tftpd if requested.
The start command as noted in inetd.conf is something like
tftpd -p -u tftp -s /tftpboot
The PXE boot-process is multi-stage:
Stage 1 is to load and start the file submitted as part of the address discovery process (usually /tftpboot/linux/pxelinux.0).
The program pxelinux.0 then looks for configuration and boot information in /tftpboot/linux/pxelinux.cfg. It first
looks for a PC specific file with a name based on the hardware ethernet address (MAC) of the network controller with
a leading 01. The filename for the controller with the hardware ethernet address 00:0C:29:11:6B:D2 would be 01-00-
0c-29-11-6b-d2. If the file is not found, pxelinux.0 will start to shorten the filename (starting at the end) to obtain
a match. If this process ends without result, the file default will be loaded. This file only contains the instruction to
boot from the local hard disk. In this case the PC won’t install anything and will just start the current OS from hard
disk.
Figure 53: Step 2 PXE-Boot
To initiate the re-installation of a certain PC, a loadable file is prepared for the program pxelinux.0. In order to do
so, the opsipxeconfd creates a PC custom file in /tftpboot/linux/pxelinux.cfg. Part of this file is the command to load