[syslinux] RedHat kickstart with PXELINUX

Peter Lister P.Lister at sychron.com
Wed Sep 4 05:37:52 PDT 2002


> We are attempting to setup an automated system to build some Linux
> systems. We have utilised the PXELINUX bootloader after encountering
> the PXE 512Kb limit with bootp.
> 
> We now have another issue which you may have already run into. In the
> DHCP configuration we specify pxelinux.0 as the bootfile, this works
> reasonable well, we call the Redhat vmlinuz and initrd.img files
> within the pxelinux.cfg/config file and the installation begins
> as expected. We would like to have a non-interactive installation
> using the Kickstart mechanism to provide the responses, the issue
> is that the installer expects to get the Kickstart file location
> from the DHCP 'bootfile' parameter which we have already used
> to provide the pxelinux.0.

Easy enough, though nothing to do with pxelinux as such.

PXE always has a 2 stage start up - when using pxelinux as the NBP, the
2nd stage gets the config via tftp, so there are no confusing multiple
dhcp requests, but if a subsequent stage uses dhcp, you need to tell the
dhcp server that replies to requests from PXE firmware have different
contents from the replies to other clients. Etherboot uses dhcp rather
than tftp, so to use Etherboot as a PXE NBP, one must always
differentiate the PXE and Etherboot dhcp requests from each other (and
those of Kickstart or Linux kernel).

Requests can be distinguished by Vendor Class ID (this is what the VCI
and other class identifiers are for). A "PXEClient" VCI is part of the
PXE spec, so you should be able to rely on it. Use ISC dhcpd v3 if you
don't already have it (this is possible with v2, but v3 is better). If
the Kickstart request doesn't include a VCI the kickstart values will
need to be the "no VCI" default (and Red Hat should fix this). You can
see the request contents with log statements in the dhcpd config - look
at the dhcpd docs.

For an example, look at http://www.ltsp.org/documentation/pxe.howto.html
- this differentiates PXE from Etherboot, rather than Kickstart, but the
principle is similar.

Read http://www.stanford.edu/~alfw/PXE-Kickstart if you haven't already.





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