After an automatic update of CentOS to version 7.7 on Sep 17 2019 my QEMU/KVM virtual machines do not start when I reboot the hypervisor server.
Trying to start the VM by hand gives this error:
# virsh start mygreatvm error: failed to connect to the hypervisor error: no connection driver available for <null>
Trying to list currently defined VMs (the VMs in questions are set to start by default (autostart) on every boot so they should at least appear here):
# virsh list error: failed to connect to the hypervisor error: no connection driver available for <null>
There are no error messages in system logs and neither in
/var/log/libvirt/qemu/*.log. The libvirt daemon seems to run fine and does not complain about the non-started servers in
# systemctl status libvirtd ● libvirtd.service - Virtualization daemon Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2019-09-18 16:42:30 UTC; 2min 49s ago Docs: man:libvirtd(8) https://libvirt.org Main PID: 1817 (libvirtd) Tasks: 16 (limit: 32768) CGroup: /system.slice/libvirtd.service └─1817 /usr/sbin/libvirtd Sep 18 16:42:30 server systemd: Starting Virtualization daemon... Sep 18 16:42:30 server systemd: Started Virtualization daemon.