[libvirt] [PATCH] Openvz: how to use a nondefault config

[Evgeniy Sokolov]

> 2009/4/2 Daniel P. Berrange <berrange at redhat.com 
> <mailto:berrange at redhat.com>>
> 
>     On Thu, Apr 02, 2009 at 06:36:15PM +0400, Evgeniy Sokolov wrote:
>      >
>      > Config /etc/vz/conf/ve-XXX.conf-sample define there are many
>     parameters
>      > like  memory, CPU etc. This parameters are not properties of
>     <filesystem>.
>      >
>      > Daniel, usage of pre-defined configs in really usefull. Can we create
>      > additional tag inside <domain></domain>?
> 
>     The trouble with this is that given the XML config of a guest, you can
>     no longer determine what its configuration is, because a large amount
>     of configuration is hidden in this opaque 'template'.
> 
> 
> And in kvm/qemu case there is a lot of hidden information too :)
> In OpenVZ case we don't loose any info (see below).
> 
> 
> 
> 
>     If we're to support templates, I think we need to make them first class
>     objects, so you can query what templates exist, and see their associated
>     config settings.
> 
>     eg, expose a simple API
> 
>       virDomainTemplatePtr;
> 
>       int virConnectListDomainTemplates(virConnectPtr conn, const char
>     **names);
>       virDomainTemplatePtr virDomainTemplateLookupbyName(virConnectPtr
>     con, const char *name)
>       char *virDomainTemplateGetXMLDesc(virDomainTemplatePtr tmpl);
>       virDomainTemplatePtr virDomainTemplateDefineXML(virConnectPtr
>     conn, const char *xml)
>       int virDomainTemplateUndefine(virDomainTemplatePtr tmpl);
>       int virDomainTemplateFree(virDomainTemplatePtr tmpl);
> 
> 
> 
>     Then, we could either include a <template>$NAME</template> parameter in
>     the XML for a guest. Or have an alternate API for creating guests
> 
>       virDomainCreateXMLWithTemplate(virConnectPtr conn,
>                                      const char *xmlDesc,
>                                      const char *template)
> 
>     It depends whether we'd want to track the template <-> guest association
>     forever, or just use it once to fill-in the guest XML and then forget
>     about the template after that.
> 
Template <-> guest association don't need. Information is used only once.

So, we will extend libvirt API by
       virDomainCreateXMLWithTemplate()
and will include <template>$NAME</template> to <domain></domain>.

Daniel, is it correct?

> 
> It doesn't matter in OpenVZ case: template (or, "config", in openvz 
> terminology) is used only
> once, when container is creating. But then per-container "copy" is created,
> and it is already used by libvirt to keep information about container. 
> Per-container
> OpenVZ config keeps the name of the original config (in ORIGIN_SAMPLE 
> variable).
ORIGIN_SAMPLE is not used by OpenVZ, and don't need. It is saved to 
config for using external tools.
> 
> Is there need for "Template API" in case of other hypervisors?
> 
> 
> 
> ------------------------------------------------------------------------
> 
> --
> Libvir-list mailing list
> Libvir-list at redhat.com
> https://www.redhat.com/mailman/listinfo/libvir-list