On 06.07.2015 10:20, vt wrote:
Hi.
If a base qcow2 image snapshot chain like this:
base.qcow2: [A] -> [B] -> [C]
[C] is the current image where guest read/write to,usually we create a
new image base on the base.qcow2 like this
qemu-img create -f qcow2 -o backing_file=/path/base.qcow2 new.qcow2
so the data of new.qcow2 is from [C] of base.qcow2, assuming the
new.qcow2 has not been write to since created.
What I want is that the data of new.qcow2 is from [B] of base.qcow2,
like this:
qemu-img create -f qcow2 -o
backing_file=/path/base.qcow2,backing_snapshot=B new.qcow2
Can the qemu support it now?
Thanks
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vt
Hi vt,
I don't think this is possible. For this to work, the snapshot would
have to be loaded temporarily, but the only place I can see in the qemu
code base where this is done is inside qemu-img and qemu-nbd, so qemu
itself appearently does not support this.
What you can do is export the snapshot via qemu-nbd (-l) and then use
that NBD server as a backing file with qemu. This is not very nice, but
I don't suppose there are many people eager to implement the
functionality you'd like to have (although I don't think it would be too
difficult, frankly…).
Max
