[libvirt] RFC: add new API to known if domain has been updated
Daniel P. Berrange
berrange at redhat.com
Mon Nov 15 10:56:58 UTC 2010
On Mon, Nov 15, 2010 at 10:26:22AM +0800, Osier Yang wrote:
> Hi, all
>
> Suppose that one updated a domain, and want to restart the
> domain with original configuration.
>
> However, currently, unless shutdown the domain first, and then
> restart or reload libvirtd, otherwise domain will still be started
> with changed configuration. e.g.
>
> # virsh list --all
> Id Name State
> ----------------------------------
> 1 f14 running
>
> # virsh dumpxml f14 | grep -A 7 cdrom
> <disk type='file' device='cdrom'>
> <driver name='qemu' type='raw'/>
> <source file='/var/lib/libvirt/images/cd1.iso'/>
> <target dev='hdc' bus='ide'/>
> <readonly/>
> <alias name='ide0-1-0'/>
> <address type='drive' controller='0' bus='1' unit='0'/>
> </disk>
>
> # virsh update-device f14 cd2.xml
>
> # virsh dumpxml f14 | grep -A 7 cdrom
> <disk type='file' device='cdrom'>
> <driver name='qemu' type='raw'/>
> <source file='/var/lib/libvirt/images/cd2.iso'/>
> <target dev='hdc' bus='ide'/>
> <readonly/>
> <alias name='ide0-1-0'/>
> <address type='drive' controller='0' bus='1' unit='0'/>
> </disk>
>
> # virsh destroy f14
> # virsh start f14
>
> # virsh dumpxml f14 | grep -A 7 cdrom
> <disk type='file' device='cdrom'>
> <driver name='qemu' type='raw'/>
> <source file='/var/lib/libvirt/images/cd2.iso'/>
> <target dev='hdc' bus='ide'/>
> <readonly/>
> <alias name='ide0-1-0'/>
> <address type='drive' controller='0' bus='1' unit='0'/>
> </disk>
>
> it's caused by libvirtd doesn't known if a domain is updated or not,
> it updated the domain configuration in memory, but client could
> not known about it.
>
> As a result, one wants to start the domain with original configuration,
> he has to shutdown the domain first, and then restart libvirt.
This is a bug. libvirt should save a copy of the original configuration
at the time the guest starts, so any live changes only remain for the
duration of that boot and automatically revert at shutdown.
Regards,
Daniel
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