Just posting this here for my reference and in case anyone else is experiencing having some instances not starting reliably in OpenStack. The discussion here finally gave me the hint to figure out a work around for my issue, and this seems to be the closest bug report/discussion to what I am experiencing? I am following the basic OpenStack install instructions using Ubuntu 18.04 server editions with OpenStack Stein. I had gotten a good flat provider network working, and was able to create instances from images and ssh into them. However, after creating 1 or 2 instances, instance startup was randomly failing and appearing to time out. About 1 time in 4 attempts the instance would start, but the rest of the time startup would fail. I had originally been looking at possible kvm/virtualization issues that were causing the vm to pause and never resume while being created, but this ultimately didn't appear to be my issue. In my nova-compute.log on the compute node where an instance was being created and started, I was seeing the following messages: ------------------- 2019-05-20 13:05:52.868 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Attempting claim on node lion-compute-1-01: memory 2048 MB, disk 5 GB, vcpus 1 CPU 2019-05-20 13:05:52.869 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Total memory: 12058 MB, used: 4608.00 MB 2019-05-20 13:05:52.869 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] memory limit not specified, defaulting to unlimited 2019-05-20 13:05:52.870 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Total disk: 65 GB, used: 10.00 GB 2019-05-20 13:05:52.870 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] disk limit not specified, defaulting to unlimited 2019-05-20 13:05:52.871 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Total vcpu: 16 VCPU, used: 2.00 VCPU 2019-05-20 13:05:52.872 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] vcpu limit not specified, defaulting to unlimited 2019-05-20 13:05:52.873 32022 INFO nova.compute.claims [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Claim successful on node lion-compute-1-01 2019-05-20 13:05:53.626 32022 INFO nova.virt.libvirt.driver [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Creating image 2019-05-20 13:05:54.113 32022 WARNING nova.compute.manager [req-0f2c0ac8-e241-4a68-9456-0839338eb43b f1e2da0af9df4165bafc5d48f5676792 8b3105f3fa3245f78a2292402a1411fb - default default] [instance: 0ce58e2e-a09e-458d-9014-e71f41094ba1] Received unexpected event network-vif-plugged-bdd60ae2-74d8-4951-9fb5-eaed9cfb60ec for instance with vm_state active and task_state None. 2019-05-20 13:05:56.879 32022 INFO os_vif [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] Successfully plugged vif VIFBridge(active=False,address=fa:16:3e:11:ae:ca,bridge_name='brqb6a95cfc-cb',has_traffic_filtering=True,id=dd59cecd-8ae6-4ada-9c11-7a5f896778d8,network=Network(b6a95cfc-cb94-4610-b354-39442c1d1b12),plugin='linux_bridge',port_profile=,preserve_on_delete=False,vif_name='tapdd59cecd-8a') 2019-05-20 13:05:57.220 32022 WARNING nova.compute.manager [req-0d0020b5-7485-4dc5-93ce-50a8a57b9001 f1e2da0af9df4165bafc5d48f5676792 8b3105f3fa3245f78a2292402a1411fb - default default] [instance: 0ce58e2e-a09e-458d-9014-e71f41094ba1] Received unexpected event network-vif-plugged-bdd60ae2-74d8-4951-9fb5-eaed9cfb60ec for instance with vm_state active and task_state None. 2019-05-20 13:05:58.441 32022 INFO nova.compute.manager [req-db477014-547a-4103-b83c-0c57ded3b145 - - - - -] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] VM Started (Lifecycle Event) 2019-05-20 13:05:58.494 32022 INFO nova.compute.manager [req-db477014-547a-4103-b83c-0c57ded3b145 - - - - -] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] VM Paused (Lifecycle Event) 2019-05-20 13:05:58.583 32022 INFO nova.compute.manager [req-db477014-547a-4103-b83c-0c57ded3b145 - - - - -] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] During sync_power_state the instance has a pending task (spawning). Skip. 2019-05-20 13:06:00.220 32022 WARNING nova.compute.manager [req-65ec8c9c-7fea-46b0-ba11-a2ce10075844 f1e2da0af9df4165bafc5d48f5676792 8b3105f3fa3245f78a2292402a1411fb - default default] [instance: 0ce58e2e-a09e-458d-9014-e71f41094ba1] Received unexpected event network-vif-plugged-bdd60ae2-74d8-4951-9fb5-eaed9cfb60ec for instance with vm_state active and task_state None. ** The previous unexpected network-vif-plugged warning repeats about every 3 seconds here for 5 minutes 2019-05-20 13:10:32.347 32022 INFO nova.virt.libvirt.imagecache [req-b0747c3b-818f-4f40-9242-0175e171e2f1 - - - - -] image 1df6f1d9-ad32-4a20-bfd6-67589d267b82 at (/var/lib/nova/instances/_base/a97e1ab707a49a2c4772328d0e440a2e19174b62): checking 2019-05-20 13:10:32.567 32022 WARNING nova.virt.libvirt.imagecache [req-b0747c3b-818f-4f40-9242-0175e171e2f1 - - - - -] Unknown base file: /var/lib/nova/instances/_base/7fc6a3f6299c3dddd0084bd4161c2a0ef492c25b 2019-05-20 13:10:32.568 32022 INFO nova.virt.libvirt.imagecache [req-b0747c3b-818f-4f40-9242-0175e171e2f1 - - - - -] Active base files: /var/lib/nova/instances/_base/a97e1ab707a49a2c4772328d0e440a2e19174b62 2019-05-20 13:10:32.569 32022 INFO nova.virt.libvirt.imagecache [req-b0747c3b-818f-4f40-9242-0175e171e2f1 - - - - -] Removable base files: /var/lib/nova/instances/_base/7fc6a3f6299c3dddd0084bd4161c2a0ef492c25b 2019-05-20 13:10:32.570 32022 INFO nova.virt.libvirt.imagecache [req-b0747c3b-818f-4f40-9242-0175e171e2f1 - - - - -] Base or swap file too young to remove: /var/lib/nova/instances/_base/7fc6a3f6299c3dddd0084bd4161c2a0ef492c25b 2019-05-20 13:10:35.013 32022 WARNING nova.compute.manager [req-a2ad0d45-186c-4b79-a85f-90da5ec2922e f1e2da0af9df4165bafc5d48f5676792 8b3105f3fa3245f78a2292402a1411fb - default default] [instance: 0ce58e2e-a09e-458d-9014-e71f41094ba1] Received unexpected event network-vif-plugged-bdd60ae2-74d8-4951-9fb5-eaed9cfb60ec for instance with vm_state active and task_state None. ** Many more unexpected event network-vif-plugged messages 2019-05-20 13:10:58.445 32022 WARNING nova.virt.libvirt.driver [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Timeout waiting for [('network-vif-plugged', 'dd59cecd-8ae6-4ada-9c11-7a5f896778d8')] for instance with vm_state building and task_state spawning.: eventlet.timeout.Timeout: 300 seconds 2019-05-20 13:10:58.883 32022 INFO os_vif [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] Successfully unplugged vif VIFBridge(active=False,address=fa:16:3e:11:ae:ca,bridge_name='brqb6a95cfc-cb',has_traffic_filtering=True,id=dd59cecd-8ae6-4ada-9c11-7a5f896778d8,network=Network(b6a95cfc-cb94-4610-b354-39442c1d1b12),plugin='linux_bridge',port_profile=,preserve_on_delete=False,vif_name='tapdd59cecd-8a') 2019-05-20 13:10:58.884 32022 INFO nova.virt.libvirt.driver [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Deleting instance files /var/lib/nova/instances/5d14418e-c766-4fe1-b1d1-fdc0bef4d90d_del 2019-05-20 13:10:58.885 32022 INFO nova.virt.libvirt.driver [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Deletion of /var/lib/nova/instances/5d14418e-c766-4fe1-b1d1-fdc0bef4d90d_del complete 2019-05-20 13:10:59.035 32022 ERROR nova.compute.manager [req-76c24954-2ce4-485d-84cd-ead03c6b403e 75e2bcf2a0f2497fb08f18b00b38446a ed5341aae98f48bbbdfa72887f32a79c - default default] [instance: 5d14418e-c766-4fe1-b1d1-fdc0bef4d90d] Instance failed to spawn: nova.exception.VirtualInterfaceCreateException: Virtual Interface creation failed -------------------- It appears to me from this log sequence that the instance is correctly allocated and created on the compute node. But then the VM is started, then VM paused then the VM is never restarted. It looks like when instance startup works for me, the pause is normal, but I guess they successfully receive the vif they are looking for and they resume the instance? In any case, I did not find this documented explicitly anywhere, but in Stein their appear to be parameters in the nova.conf file now that one can set to effect the timeout period and whether vif plugging/unplugging should be considered fatal to instances. Maybe these were added specifically for people with issues like mine? In any case, changing these settings in /etc/nova/nova.conf on my compute nodes allows for reliable instance creation and startup now on my OpenStack installation: compute node /etc/nova/nova.conf vif_plugging_is_fatal = false vif_plugging_timeout = 0 Though since I am not familiar with what vif plugging is, I'm not sure if there are other implications of ignoring these in my OpenStack installation going forward.