On Mon, Aug 25, 2025 at 08:37:24 -0400, Philip Bondi wrote:
> Hello libvirt users:
>
> On QNAP platform, this is my outcome from the following step "2. Enumerate
Were you unable to use the 'virDomainBackupBegin' API? (virsh
backup-begin) ?
> the current block device(s) in use, again. Notice that the current disk
> image in use is the above-created overlay, overlay1.qcow2:" I'm showing
> both pre- and post-execution from the shell.
>
> There's 2 files. Should both files be purged according to the instruction
> "Now you can safely discard the overlay image"?
>
> + virsh domblklist 9c7d2c4d-9c28-44bd-8da9-642a63b25c39
> Target Source
> -------------------------------------------------------------------------------
> vda /share/Virtual-Machines/SHACKLETON1210/SHACKLETON1210_00.1755932401
> hda /share/Virtual-Machines/debian-12.10.0-amd64-netinst.iso
>
> ls -alF
> /share/CACHEDEV2_DATA/Virtual-Machines/SHACKLETON1210/SHACKLETON1210_00.1755932401*
> -rw-r--r-- 1 admin administrators 177602560 2025-08-23 05:02
> SHACKLETON1210_00.1755932401
> -rw------- 1 admin administrators 40470118400 2025-08-23 03:42
> SHACKLETON1210_00.1755932401.1755934525
Unfortunately you are showing only one output and didn't post the exact
steps that lead to this situation. Since deleting files could lead to
data loss in certain situations you will need to verify which images are
used and which are not.
To do that look at the VM xml (virsh dumpxml) and verify which images
are in the backing chain of the disk that you've backed up. The chain
looks like:
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/var/lib/libvirt/images/rhel7.1484071880'/>
<backingStore type='file'>
<format type='qcow2'/>
<source file='/var/lib/libvirt/images/rhel7.qcow2'/>
<backingStore/>
</backingStore>
<target dev='vdf' bus='virtio'/>
</disk>
It can have more nested <backingStore> entries. All of the images
captured by the XML are *in use* and must not be deleted.
In short you should delete only the temporary overlay that you've
created via 'virsh snapshot-create-as' and only after it was succesfully
merged via blockcommit.
