On 5/16/19 10:20 AM, Thomas Stein wrote:
Hello all.
My currently used versions: libvirt-5.2.0 and qemu-4.0.0.
Here is my problem. I'm struggeling since a few weeks with a strange behaviour by either qemu or libvirt. After a reboot of the hardware node the $domain.xml contains suddenly a backingStore setting which was not there before reboot. Something like that:
<devices> <emulator>/usr/bin/qemu-system-x86_64</emulator> <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/var/lib/libvirt/shinymail/shinymail_weekly.qcow2-2019-05-15'/> <backingStore type='file'> <format type='qcow2'/> <source file='/var/lib/libvirt/images/shinymail.qcow2'/>
Yes, this matches:
</backingStore> <target dev='vda' bus='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> </disk> ...
This obviousely happens after a backup has been running. The Backup Script looks like this:
<snip> virsh snapshot-create-as --domain shinymail weekly --diskspec vda,file=/var/lib/libvirt/shinymail/shinymail_weekly.qcow2-$(date +%Y-%m-%d) --disk-only --atomic --no-metadata
the effects of this command. Ultimately, I'm TRYING to get my new 'virsh domain-backup' command integrated into the next libvirt release, which has the advantage of performing a backup WITHOUT having to modify the <domain> XML. But until that happens, any time you use 'virsh snapshot-create-as' as part of a sequence for performing backups, you ARE modifying the <domain> XML, and if you want to revert to the external backup, or if...
cp ...
virsh blockcommit shinymail vda --active --verbose --pivot <snip>
...blockcommit fails for whatever reason to undo the effects of 'snapshot-create-as' in creating a temporary overlay, then yes, you do have to worry about the temporary overlay being in the way, where you'll have to manually edit the <domain> definition to match the actual disk layouts you really want.
So after that "dmblklist shinymail" does show the right source file but after a reboot it tries to use the weekly snapshot again which leads to filesystem errors.
Someone has an idea what could cause such a behaviour?
-- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org