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[libvirt] offline migration / vm cloning with libvirt/virsh



Hi ,


I am trying to perform offline migration (i.e) Create an incremental image using the qcow format, transfer the vm memory state to a state fie.Use the image and statefile together as a template. Now create a new vm using the template. I can successfully do it using the following commands : 


Save phase :

stop

migrate "exec:gzip -c > STATEFILE.gz"

qemu-img 

qemu-img create -b BASE_img -f qcow2 INCRE_img


Restore phase :

qemu-kvm -m 1024 -hda INCRE_img -incoming "exec: gzip -c -d STATEFILE.gz"


And it works fine. But I am not able to find the vm with virt-manager or other libvirt based tools.


If I use : 

virsh save <dom_id> STATEFILE


I can restore using "virsh restore STATEFILE" but I want to associate this with the incremental image that I created, but I dont know how. I think it saves the existing vm's xml file along with the STATEFILE, thus I am not able to change the disk image to the incremental image.


Thus ,

1. Either I should find a way to make vms created using qemu-kvm appear in libvirt-based tools.


OR 


2. Find a way to associate the virsh save STATEFILE with a incremental image. 


Any help or hint with respect to these will be very helpful. I am try to do cloning with minimal cost. This takes only 25 seconds ( to create STATEFILE) and creating incremental image is instantatenous . But I want to use the vm monitoring code based on libvirt. And it makes life difficult. 


Thanks for your help. 


-

Regards,

Sethuraman Subbiah


Graduate Student - NC state University

M.S in Computer Science


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