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.

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.

--
Bob Nichols     "NOSPAM" is really part of my email address.
                Do NOT delete it.

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