The trick that Rocks uses is to have a boot order of (hard disk, pxe)
and then when you want to reinstall, change two bytes in the
boot sector to make the hard disk unbootable and it will fall through
to a PXE boot only at that time.

What worker node installs at Fermilab do is to have a DHCP server that
only answers the PXE request when you want to reinstall, and no other
time, so the PXE request just times out and then you boot off the hard 
drive.

Steve

On Mon, 17 Oct 2011, ~Stack~ wrote:

> Hello All,
>
> I ran into another issue with my PXE build out. I searched the net and
> found many people with the same issue, but there was either no response
> or their solution would not work for my needs (requiring access to
> software I don't have). What I am after with this is a completely
> unmanaged automated install of a client on boot.
>
> I am using dnsmasq as my DNS, DHCP, and TFTP server.
>
> I have a server and a client. The client boots off the network card with
> PXE. It asks for and receives a IP from the DHCP server and proceeds
> with pulling the TFTP information. The TFTP server passes it a
> pxelinux.0 file along with the "default" configuration. The
> configuration has a kickstart file and the client continues with a
> flawless install of SL6.1. After the install, the client reboots...and
> the whole process starts over and over and over again. I know why it
> does this (the default boot option is to install), but I can't figure
> out how to control it.
>
> What I would like is a process where I boot the clients from an off
> state, have them do a fresh install, and then reboot into the new
> install. Nothing is stored on these nodes and a fresh install goes
> rather quickly so I don't mind this option.
>
> At first I tried scripting an option that just toggled the tftp default
> menu but it wasn't working very smoothly as not all my hosts boot at
> equal speeds.
>
> I attempted chainloading in the tftp but just made a mess and I didn't
> get any different results. Most likely due to me not understanding it
> properly. I am open to pointers.
>
> I thought I could do it inside of DNSMasq, but I couldn't find a good
> example and my attempts didn't work.
>
> I looked online and found projects like systemimager.org but I am
> already doing most of what they provide. I attempted to reverse their
> perl scripts but that is a bigger project then I initially thought. What
> I did like about this project was the ability to tell it to allow a
> single host or a group of hosts to reinstall or to boot off the hard disk.
>
> I have gotten some great pointers from this list so far and I am really
> hoping someone might have another for me. Any ideas?
>
> Thanks!
>
> ~Stack~
>

-- 
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
[log in to unmask]  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Group Leader.
Lead of FermiCloud project.