[syslinux] PXElinux question - not in FAQ (additional DHCP options)

Josef Siemes jsiemes at web.de
Fri Mar 7 09:18:21 PST 2003


sorry if you got this mail  without contents - seems that return sends the mail here ...

Woody Suwalski <woody at suwalski.net> schrieb am 07.03.03 17:57:26:
> Now I am trying to build a network boot for Xandros distribution.
> I have it working, however I need to do 2 DHCP cycles - 1 happens in 
> PXE, and then it repeats in my network boot code (based on BusyBox). All 
> I need in the second stage is the NFS image address, passed by DHCP as
>     option root-path "dell:/XandrosInstallCD";

It seems that you could just define this, without any changes.

pxelinux needs the server address and the boot file options
(DHCP options 66 & 67, ISC dhcp options next-server and filename),
and doesn't interest in the root-path option.

Did you already try this? Since it seems that you already did this without
success: Does your second DHCP request ask for the root-path option,
and did the server give it to the client? DHCP has a mechanism where the
client specifies which options it wants from the server, and the server
in turn responds with the defined options for this client. More on this is in
the various DHCP RFCs. AFAIK ethereal (or even tcpdump?) reports which 
options were requested by the client.

> Unless I could use your PXELINUX_MAGIC option. Since I do not need extra 
> config files, I could use the field to specify NFS root. But how to pass 
> it later to the kernel?

Give every client an own config file, and let these have something like

default bla
label bla
  kernel mykernel
  append root-path=<root path of this client> [further client-specific options]

in this file. With this workaround every client would get its specific
kernel parameters, and these would be interpreted by the boot 
process (initrd, init-scripts or else). You could generate these by a script,
getting the data from one central source.



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