On 03/28/2017 10:28 AM, Patrick O'Callaghan wrote:
On Tue, 2017-03-28 at 09:13 -0500, Robert Nichols wrote:
On 03/27/2017 12:31 PM, Patrick O'Callaghan wrote:
I have a QEMU image snapshot:
$ sudo qemu-img info /var/lib/libvirt/images/Windows10.qcow2
image: /var/lib/libvirt/images/Windows10.qcow2
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 196K
cluster_size: 65536
backing file: /home/poc/Win10/win10.qcow2
backing file format: qcow2
Format specific information:
compat: 1.1
lazy refcounts: true
refcount bits: 16
corrupt: false
However when I try to restore the virtual disk I get:
$ sudo qemu-img snapshot -a /var/lib/libvirt/images/Windows10.qcow2 /home/poc/Win10/win10.qcow2
qemu-img: Could not apply snapshot '/var/lib/libvirt/images/Windows10.qcow2': -2 (No such file or directory)
I must be doing something obviously wrong, but can't see what it is.
Hints would be appreciated.
What you have is not a snapshot. A snapshot is created with "qemu-img snapshot -c <snapshot-name> <imagename>", and that is _not_ a separate file. That "<snapshot-name>" is not a file name but just a tag to identify one of possibly several snapshots within that "<imagename>" file.
I did create it with the above line. Clearly I didn't understand where
it was, or perhaps I inadvertently deleted it.
That output from "qemu-img info ..." says otherwise. That /var/lib/libvirt/images/Windows10.qcow2 file was created with "qemu-img create -b /home/poc/Win10/win10.qcow2 /var/lib/libvirt/images/Windows10.qcow2". There is no other way that "backing file: /home/poc/Win10/win10.qcow2" could appear in the output.
In order for the .../Windows10.qcow2 file to be valid, that backing file _must_ exist and be unchanged since that new file was created.
Currently 'qemu-img snapshot -l <filename>' gives no output, so it
looks like it's gone assuming it was ever there.
There should not be any output. You simply do not have anything that qemu-img calls a "snapshot".
(BTW the "no such file or directory" message could not be less
helpful).
Agreed, 100%.
What you made was a copy-on-write image using /home/poc/Win10/win10.qcow2 as a backing file. You can make changes in /var/lib/libvirt/images/Windows10.qcow2 and not affect the backing file, but the backing file _must_not_be_changed_ during the lifetime of that dependent image. That c-o-w image cannot be restored to its original state. The way you do that is to throw it away and create a new one with the same backing file.
I'm going to try to attach it to another Windows instance to see if it
can be repaired. Otherwise, it looks like I'm screwed.
That backing file _must_ exist, or else you have nothing. If the backing file exists, but has changed, then the only valid image is what is currently in the backing file. If an unchanged backing file exists, you have the option to (a) throw away that /var/lib/libvirt/images/Windows10.qcow2 file and create it anew from that backing file, or (b) merge the changes that have been made in the /var/lib/libvirt/images/Windows10.qcow2 file back into the backing file. You do the latter with "qemu-img commit /var/lib/libvirt/images/Windows10.qcow2".
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.
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