[Fedora-livecd-list] Re: [PATCH] Add support for pxeboot

Chris Lalancette clalance at redhat.com
Tue Feb 12 04:03:33 UTC 2008


Richard W.M. Jones wrote:
> 
> (a) The initrd has to carry around dhclient, network scripts, and all 
> the network programs like '/sbin/ip'.
> 
> (b) The initrd has to be able to find the TFTP server again, which 
> basically involves making another DHCP query.  In Chris's original 
> implementation he also added specific DHCP options to carry the TFTP 
> server information since it wasn't clear how to get this out of stock 
> dhclient.
> 
> (c) After booting, because of (b), the network is already set up, which 
> is not how a live CD expects it to be.  Therefore the live CD itself 
> would need to be changed if it does any network configuration.

This turns out not to be a problem in practice; the network init scripts
are just fine re-doing all the configuration that the initrd did, it
just takes some time.  In particular, another downfall with this method
that Richard did not mention is that by the time you've actually booted,
you've DHCP'ed 3 times on the same interface; once to find your PXE
server and TFTP the kernel/initrd, once in the initrd to fetch your root
filesystem, and finally a third time to bring the interface up for real.
 Each of these takes time, slowing down the boot process.  In Richard's
version, this is reduced to two DHCP's; the first one to fetch
everything via PXE, and the second in the network init scripts.

Chris Lalancette




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