opsi Version 3.3.1 - opsi Download - uib

5. Netboot products: Automated OS installation and more
At first the PC only knows its hardware ethernet address (MAC), consisting of six two-
digit HEX characters.
The firmware initiates a DHCPDISCOVER broadcast: “I need an IP address, who is my
DHCP-Server?“
The DHCP-Server offers an address (DHCPOFFER).
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.
5.1.3.1. 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:
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