Diskless PXEboot crashes at kernel loading.

Sam Baskinger sbaskinger at lumeta.com
Mon Feb 19 08:08:30 UTC 2007

Hi all,

I can't emphasise enough how useful running a TCPDUMP on the server
in question is to find out what subtle thing it is that I missed.

Generally speaking a quick-crash like that is a file not being found like
the modules directory or something silly like that. If you dump the NFS 
traffic you will probably see the client asking for a file handle for
file X and getting denied by the server.

If you're not familiar w/ TCPDUMP, here are some handy commands:

# Avoid SSH and dump everything to the screen...
tcpdump -s 1500 -X udp

# Write it to a file so you can open it in ethereal later...
tcpdump -s 1500 -X -w nfs.dump udp

# Read in the dump file and read it through less, should you not want to us
# ethereal after the last step. :)
tcpdump -X -r nfs.dump |less

Note that if you have a slow or missing DNS entry, give these calls a -n
to just get the data and not worry about the ND entries.

Hope this helps! PXE boots are never kind. :)

Sam Baskinger
Software Engineer

Lumeta - Securing the Network in the Face of Change

Lumeta Corporation

> > And the crash happens.
> > Note that the crash occurs for whatever option
> > 1 to 6 I choose from the FreeBSD boot menu.
> > Does someone understand the crash messages?
> Not that I understand those messages but some time ago I've had a
> similar case. It took me some hours to realise that I try to load
> amd64 kernel to i386 diskless station...

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