[libvirt] [libvirt-users] virsh can't support VM offline blockcommit
kchamart at redhat.com
Tue Oct 13 13:55:01 UTC 2015
On Tue, Oct 13, 2015 at 10:39:58AM +0800, justlibvirt at gmail.com wrote:
> Hi everyone!
Firstly, please don't post the same message multiple times in a row. If
someone hasn't responded, they're either busy, or haven't noticed this
> I use the libvirt(version: 1.2.2) and QEMU(version: 2.2.1) to
> test qemu snapshot features:
> I tried virsh blockcommit when VM offline, the virsh blockcommit
> failed: the error messase as below: error: Requested operation is
> not valid: domain is not running when I start the VM, the virsh
> blockcommit work fine! my question is：we need virsh support
> blockcommit when VM offline。how do？
As near as I know, 'blockcommit' hasn't yet gotten offline support.
> we test qemu snapshot as follows： we need create snapshot of
> the cycle，and by virsh blockcommit merge snapshot chain，but
> when VM offline， the virsh blockcommit will fail， someone
> suggest me：when VM offline，may use qemu-img commit to submit
> snapshot turn，but qemu-img can't modify snapshot chain backing
> relation，it need we use qemu-img rebase amend snapshot‘s
As you note there's the 'qemu-img commit' primitive that allows you to
commit the changes in an overlay back into its base image:
If you have: base.qcow2 <-- overlay1.qcow2 <-- overlay2.qcow2
And, if you do:
$ qemu-img commit overlay2.qcow2
It'll commit the contents of overlay2.qcow2 into overlay1.qcow2.
And, indeed use the 'qemu-img rebase' to modify the backing file is the
only method I know of, for offline operations.
> the main question is when we use qemu-img rebase
> modify snapshot's backingfile, if someone start the VM, it will
> may lead to VM filesystem readonly。
Though I haven't tested this recently, why would it lead to VM
filesystem becoming read-only?
> we should how to solve the question? thanks! >
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