Ok, so this is due to your /etc/libvirt/hooks/qemu script not handling 'reconnect' and exiting with an error. When the hook script exits with an error, the existing vm is terminated. (The error is in your libvirtd.log) So adding a 'exit 0' when called with 'reconnect' will solve this for you.
I'm going to mark this bug invalid. If you feel that there is still a real bug, please comment here so we can revisit. ** Changed in: libvirt (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to libvirt in Ubuntu. https://bugs.launchpad.net/bugs/1470778 Title: Unattended upgrade of libvirt-bin and libvirt0 killed virtual machines To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1470778/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs