Re: Fwd: Re: [Xen-users] Xen 3.1, Fedora 8 and PCI passthrough

[jim burns <jim_burn@xxxxxxxxxxxxx>]

On Monday 25 February 2008 10:48:42 am Kenneth Lundström wrote:
> If I now restart the computer and then open virt-manager my test domain
> is nowhere to be found. I have to edit the config.sxp file and remove
> the section about the NIC. I insert my own text and then my domain is
> back again. Is there a way to find out what the problem might be?

It's probably not a great idea to edit the UUID/config.sxp, and definitely not 
when the guest is running. This points out the different styles virt-manager 
and the usual 'xm' usage employ. When you create a domain in virt-manager / 
virt-install, it does the equivalent of a 'virsh define xmlfile', which 
creates your UUID/config.sxp. Then to start the guest, the gui does the 
equivalent of 'virsh start domain-name(as defined in the xml file)'. When you 
shutdown, virt-manager still has the definition until you do a 'virsh 
undefine ...'. (The corresponding xm commands are xm new, xm start, and xm 
delete.)

The user who uses xm instead of a gui typically uses xm create, and xm destroy 
or shutdown (or shuts down gracefully from within the guest), which leaves no 
residual trace of the domain in the xenstore databases. It's always a good 
idea to have copies of the dumpxml, or the flat config you created from it, 
in case the xenstore definitions disappear, or are corrupted (in which case 
you erase /var/lib/xend/domains/UUID after rebooting into a non-xen kernel).

The difference between the dumpxml and the flat config is which command you 
create the domain with. virsh define/create uses xml, xm new/create uses the 
flat config. I personally always create a domain from a config, which is 
backed up along with everything else important, and don't worry about whether 
xen will remember my domain's definition w/o corruption in it's database. 
Also, having a config you can edit allows you to add more advanced features 
(like pci passthrough) that the gui can't handle. Editing a database is, 
again, probably a bad idea.

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