[K12OSN] (no subject)

Christopher Hill (chris@redhat.com)
Wed, 24 Apr 2002 23:41:32 +0100


Hi!

I've got a suggestion for a new K12LTSP feature that I don't think 
would be too hard to implement and would add a lot of value to the 
distro for the situation that our school is in at least.

We can't really separate the computers that we would like to test 
K12LTSP on from the rest of the network, so I was experimenting with 
using two DHCP servers on the network. The idea was something like this:

The Etherboot image is configured with the 'REQUIRE_VCI_ETHERBOOT' 
enabled. This means that the DHCP client will only accept leases from 
servers that put the 'Etherboot' Vendor Class Identifier in their 
replies.

The DHCP server is configured to only supply leases to clients that put 
'Etherboot' in their Vendor Class Identifiers.

The above two are possible with the current version of K12LTSP, by 
fiddling with the K12LTSP dhcp server config file. The system boots and 
gets to the point where DHClient tries to get an IP address. However, 
DHClient doesn't have the 'Etherboot' option in it's VCI, and it 
accepts leases from all servers, so it doesn't get a lease from the 
correct server, and the bootup fails.

What needs to happen are two things:

1) The DHClient needs to have a VCI set - something like K12LTSP would 
be nice :). I don't think this can be too hard.
2) The DHClient also needs to make sure it only accepts replies from 
servers that also have a certain VCI set - once again, K12LTSP would be 
a good idea. Not sure how easy this is to do.

If this happened, then basically setting up K12LTSP across a network 
would be as easy as:

1) Install the server with both interfaces plugged into the same 
network (or even one multihomed adaptor)

2) Create the Etherboot images with the 'REQUIRE_VCI_ETHERBOOT' option 
enabled.

The K12LTSP DHCP server would only respond to K12LTSP clients, and the 
normal DHCP server would respond to both clients but the leases would 
not be taken up because the K12LTSP clients will only accept leases 
from the K12LTSP server.

I hope this is fairly clear - it seems to me that for a small 
investment in time there is a real improvement available!

If you need information on how only allowing certain VCIs works under 
LTSP, try the following LTSP documentation. It is in the situation of 
needing to distinguish between PXE and Etherboot clients, but the 
principle remains the same.
http://www.ltsp.org/documentation/pxe.howto.html

Please let me know how you think and ask any questions.

Chris



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