Re: [libvirt-users] virsh can't support VM offline blockcommit
On Tue, Oct 13, 2015 at 10:39:58AM +0800, justlibvirt(a)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