Xen users - Sep 2006 - Problem running domU over a diskless XEN

Hey,

I have a XEN 3.0.2 hypervisor running as a diskless machine over NFS (booted
using PXE and DHCP)
When I run "xend start" my machine freezes and the only thing to do is
to
cold boot it.

I found that during the creation of the xenbr0 bridge, eth0 goes down and
undergoes a serious ''makeover''.
This, of course, is a very bad thing for me because as soon as eth0 goes
down or cannot maintain the
network connection, my DISKLESS machine doesn''t work anymore.

I temporarily solved the problem by using a second network adapter, eth1,
and inserting it into the beridge
instead of eth0.

My goal is to be able to start ''xend'' and run domU''s
with only one network
adapter, the same one my diskless
hypervisor uses as it''s life line. Can this be done? Is it possible to
change the ''network-bridge'' script is such a
way that the bridge will be created and the domU''s will have a network
connection without ever bringing eth0 to
a non functioning state?

Alternatively, can I configure some kind of routing mechanism to allow the
domU''s to access the network through
eth0?
Note that I''m also booting my domU''s as diskless machines over
NFS and using
the same DHCP as the hypervisor,
so and they HAVE to be a part of the same subnet as the hypervisor (e.g.
NAT/PAT is not a good solution...)

Thanks,

Tal.


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On Thursday 21 September 2006 10:39 am, Tal Maoz wrote:
> I have a XEN 3.0.2 hypervisor running as a diskless machine over NFS
> (booted using PXE and DHCP)
> When I run "xend start" my machine freezes and the only thing to
do is to
> cold boot it.
not exactly the solution you''re seeking, but have you tried to do PXE
without
NFSroot?

i mean, since dom0 is supposed to do VERY little work besides xend, you can 
create a cramfs initrd with all you need and get that via TFTP at bootup; no 
need for NFSroot on dom0.

i do that for some small servers, accessible only via SSH, SCP and thttp (no 
Xen... yet)


-- 
Javier


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On Thu, 21 Sep 2006, Javier Guerra wrote:
> On Thursday 21 September 2006 10:39 am, Tal Maoz wrote:
> > I have a XEN 3.0.2 hypervisor running as a diskless machine over NFS
> > (booted using PXE and DHCP)
> > When I run "xend start" my machine freezes and the only
thing to do is to
> > cold boot it.
> 
> not exactly the solution you''re seeking, but have you tried to do
PXE without
> NFSroot?
> 
> i mean, since dom0 is supposed to do VERY little work besides xend, you can
> create a cramfs initrd with all you need and get that via TFTP at bootup;
no
> need for NFSroot on dom0.
> 
> i do that for some small servers, accessible only via SSH, SCP and thttp
(no
> Xen... yet)

that''s an interesting idea. Do you have a build environment for the
initrd
that you''d be willing to share (or suggest). Obviously it should be a
cut
down environment, not a gnu-libc one where you can''t get a static
binary
down to less than a 1/2 meg. Busybox can get you a long way, but
doesn''t
cover ssh. And xen needs a lot of python... hhmm, that would be a really 
cool project, but not a trivial one. 

(yikes, my centos python install is 20 meg, in that scale, maybe skipping 
glibc isn''t significant.)

-Tom

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