On Tue, Oct 13, 2015 at 10:39:58AM +0800, justlibvirt@gmail.com wrote:
Hi everyone!
Hi, 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 message.
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 backingfile，
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! >
-- /kashyap