[et-mgmt-tools] XenEnterprise, PXEBoot, and Koan....

Michael DeHaan mdehaan at redhat.com
Fri Sep 21 15:52:58 UTC 2007

Patrick Nixon wrote:
> Hey all,
>  I'm trying to figure out the best way to be able to pxeboot a Virtual
> Machine on our XenEnterprise server and have it build itself using
> cobbler.
koan currently does Xen paravirt and also qemu/kqemu/KVM installs.   So 
no Xen PXE as of yet.
Upstream virtinst (the library koan uses) does have Xen PXE support, but 
as it's not released quite
yet I haven't added it to koan.

Of course, you can already use Cobbler to manage the PXE config, just 
that the piece
to make koan create a new PXE virtual machine isn't in Cobbler yet.

>  Since Xen doesn't do PXEBoot, I was reading up on Koan and the livecd
> thinking I could make an ISO for Xen to boot from and then koan to the
> cobbler server and 'Presto!' it's done.

This really doesn't make sense -- and may indicate I haven't explained 
the point of the Live CD
clearly enough

That Live CD was designed for doing installs of hardware (bare metal) in 
an environment
where Cobbler was present, but DHCP could not be configured.  It's also 
a universal installer,
meaning that F7 based live CD can install any distribution, not just 
those based on F-7.  You can
walk one CD anywhere on  your network, stick it in, and have it install 
-- regardless of whether
the admin of the network has PXE configured or not -- regardless of 
whether he's set up cobbler
or not.  It points that physical machine at /your/ cobbler server.   
It's just enough to boot it, discover
the hard drives, and write grub and the neccessary details into the MBR.

However, it's not really appropriate for doing virtualized installs.   
It assumes disks already
exist and are discovered by the Boot CD, etc.   Plus it wouldn't specify 
how much RAM you need, etc.

Once PXE support is released in virtinst, I'll add some bits for koan to 
make it be able to install fullvirt
Xen -- the PXE config will come from cobbler, as will the cobbler 
settings for how much RAM to allocate
and where the disk space is.   However, the actual boot will take place 
over PXE.

Until then, you can use paravirtualized Xen or qemu/KVM with koan.   
They do not technically PXE
but they achieve the same kind of result.

>  However, I'm having trouble building the LiveCD, but I think that's
> mostly because I'm using Centos5 instead for FC7+.

The live CD must be built on F7 or higher.  The only reason we require a 
live CD to be built (vs downloaded)
is the parameters to koan (such as the boot server name, or the 
preference to autodiscover, and what
profile to install) are embedded into the CD when it's burned.

An interactive version that asks what profile to install from a list, 
however, is something that could be done
with minimal changes.  And if we did that, it could also prompt for the 
server location...

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