Hello,
I'm using a somehow old xCAT version (2.11) to provision stateless
OSimages using switch based discovery. Everything works fine but I
cannot fully understand how the whole PXE process works :
my understanding is that, starting from scratch, it goes like this :
Unknown node :
1. C: native PXE client request
2. S : xCAT answers by providing xnba
3. C: xnba make another PXE request
4. S : xCAT answers by providing the 'net'
(/tftpboot/xcat/xnba/nets/<net>) gpxe script
5 C : xnba executes the 'net' gpxe script which http-downloads genesis
image which kernel is given the BOOTIF parameter : expanded to what ?
[genesis does its job. BTW : I thought a nodeset was done at the end of
chain to instruct to next boot on the final osimage (provided 'osimage='
ends up chain) but it does not seems to be an exactg equivalent to
nodeset since the prescripts in that context aren't executed : am I right ?]
1. - 3. : same as above
4. S: xCAT answers by providing the 'node'
(/tfptboot/xcat/xnba/nodes/<node>) gpxe script
5 C : xnba executes the 'node' gpxe script which http-downloads the
final osimage which kernel is given the BOOTIF parameter : expanded to
what ?
Though my setup works, I'm having a hard time figuring out exactly what
are the use/relevance and links (if any) between
[install|primary|discovery]nics in the noderes table and the BOOTIF
kernel parameter as well as what exactly gets BOOTIF expdanded to.
I'm (successfully) provisionning on nodes like this
- eth0, eth1 : 2 built-in 1G ethernet interfaces
- eth2 : 1 additionnal PCI-E 10G ethernet card
- bios configured to PXE through the latter (eth2)
So it seems to me everything from the first native PXE request to the os
image download, goes through this 10G/eth2 interface. This is as a
matter of fact what I want.
But :
- how is it that it works in spite of my noderes table being set up
(probably from a previous trial) like this :
"compute",,"xnba","xcat",,"xcat",,,"eth1","eth0",,,,,,,,,,,
-> installnic is == eth1
- how does (step 2. above) xnba "know" what interface to use for it's
own PXE request since no BOOTIF nor kernel has been passed yet ?
Thanks
--
Thomas HUMMEL
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