Edubuntu does not work with DHCP Konfiguration on port 1067

[mailing-joergd at gmx.net]

> Hi,
> 
> On Mon, 07 Aug 2006, mailing-joergd at gmx.net wrote:
> 
> > The classroom is already running a terminal server solution, which uses
> > pxe. But it is a commercial solution, not very flexible. My task is to
> > implement a thinclient solution WITHOUT touching the existing system. A
> > testbed server is available, the clients will be booted via diskette.
> > AFAIK, the best possibility to realize this is shifting edubuntu to work
> > on dhcp port 1067.
> 
> Instinctively, running DHCP on two different ports with modified DHCP
> clients sounds horrible but whatever works for you :-)
> 
> For what it's worth, I would be more inclined to shut down the DHCP on one
> or other system and configure the other DHCP server to handle both
> systems.
> That way you can use a standard PXE setup on clients and just reconfigure
> the DHCP server to dictate which machines get Edubuntu and which get the
> other system.  

The clients should be able to boot the existing system as well as Edubuntu.
That's why a distinction based on the machines is not practicable. A pxe multiboot solution might work, but I'd prefer a solution where edubuntu works independent of the other system. The users just should put in the etherboot-diskette if they would like to boot edubuntu.
 
> Modified DHCP clients seems counter to the whole point of DHCP, but that's
> just my instinct.

You're instict is definitely right... :-)

> > I've done these steps: - Changed the dhcp server port in
> > /etc/init.d/dhcp3-server - Configured a diskette via rom-o-matic.net to
> > work on port 1067/1068 (ALTERNATE_DHCP_PORTS_1067_1068)
> 
> The Edubuntu thin client system needs to be told to use port 1067. I guess
> you  should be able to modify dhclient.conf to tell it to use a different
> port but I can't find this option documented anywhere.  I do see in the
> manpage of dhclient that it can be passed port options on the command
> line,
> eg "-p 1068" so I'd imagine there should be a config file option.  

Yes, but how to implement this option in the client image?
I'm not sure that the second dhcp request (the one which causes the trouble) is triggered by the nfs mounted /opt/ltsp/i386.

If 2nd dhcp request fails, the client crashes down to the busybox.
After 2nd dhcp request succeeds, the client starts mounting its filesystem over nfs.

I think the dhcp request is started by the vmlinuz/initrd.img image located in /var/lib/tftpboot/ltsp.

Is this correct?

> If it came to it, you could rebuild the dhcp3-client package and install
> it
> into your edubuntu chroot with the default port number changed in the
> source.  (ick!)  It looks like you need to look at client/dhclient.c line
> 298.

Hmmm I'm pessimistic after trying to build my own kernel already failed...

> > The client's first dhcp request is correctly answered, and he gets his
> > linux image via tftp. So far so good...
> > 
> > Unfortunately, there's trouble when the client sends his second dhcp
> > request. He gets the wrong ip configuration, as he asks the wrong (the
> > existing) dhcp server. Consequentially, the client is unable to mount
> the
> > nfs.
> 
> That sounds about right.
> 
> > As far as I understood, the option-129 setting only works with etherboot
> > images. Edubuntu does not deliver etherboot images by default.
> Therefore,
> > I created a etherboot image as described at
> > https://help.ubuntu.com/community/UbuntuLTSP/LTSPEtherbootSetup .
>
> Sorry, I don't know enough about this stuff to be of much help.  However,
> I
> guess the ultimate goal must be to convince dhclient to use the other port
> so I'm unclear exactly how dhclient gets passed this info.  

These option settings are used to bypass specified options (like DPORT)
to the client kernel. As described, the kernel delivered with ltsp_initrd_kit recognizes the DPORT setting. For other people using the ltsp package it seems to work with the option settings, too (take a look at the ltsp mailing list).
 
How are the edubuntu images in /var/lib/tftpboot/ltsp created? Is there any chance to adapt them without having to make a new kernel? What are the differences between the edubuntu images and the ltsp images?

> > option option-129 "DPORT=1067";
> 
> Just a small thing.  If you want DHCP on 1067,1068, dhclient needs to be
> passed the command line "-p 1068" (otherwise it uses 1066,1067).  I
> presume
> that's not your problem (or you'd be getting no dhcp response).  Just a
> thought.

Did not help, I think DPORT=1067 means that the dhcp server port is 1067, which would be ok.

> Sorry I can't help more,
> Gavin

Thanks a lot for your help,
hopefully we can fix this issue somehow.

Best Regards
Jörg Deutschmann
-- 


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