[kernel-xen] DomU fails to start after power outage

Steven Haigh netwiz at crc.id.au
Fri Nov 9 08:25:55 EST 2012

On 9/11/2012 4:14 AM, Steven Spencer wrote:
> In looking at your template config, I'm wondering if we are simply doing
> things wrong here. If so, then we've been doing them wrong for a very
> long time. When we create a new domain, we generally use virt-install
> with prompts, If we were to use your template system, would this give us
> a more reliable way to restore a domain given this situation in the future.
> I'm still off-line by the way. Mostly because I'm not sure how to
> restore the vif.

Ahhh - another victim of libvirt.

While I can see the idea behind libvirt, and while I have much respect 
for RedHat, I really see libvirt as a bandaid that RH came up with 
because they pulled Xen support with RHEL6. As such, they needed a tool 
for enterprise customers that will eventually make it so that it would 
be a single interface for KVM, Xen etc etc.

That may be a noble idea, but its not there yet. My thoughts on it at 
the current state is that it merely adds another stage of extraction and 
another point of failure for something to go wrong. Its not required, so 
I don't recommend to use it. Its also why I don't build a libvirt with 
my Xen packages - and that is ignoring that libvirt is not yet 
compatible with Xen 4.2!

The traditional way to create Xen VMs has always been via /etc/xen and a 
config file. Its hand created and most large companies create their own 
scripting to manage these. As such, you have complete and easy control 
over the VM configuration. The config format is VERY simple and there 
isn't really much to go wrong.

If virt-install creates the XML config (urgh), you may be able to 
convert the XML to normal config using libvirt.

The syntax is:
$ virsh -c xen:/// domxml-to-native xen-xm rhel5pv.xml

This will output a plain text config file. For compatibility, you can 
also go the other way:
$ virsh -c xen:/// domxml-from-native xen-xm rhel5.cfg

Steven Haigh

Email: netwiz at crc.id.au
Web: http://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299

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