[one-users] unable to attach disks to VMs: 'driver' expects a driver name and other error messages

[Lars Buitinck]

Dear all,

I've been struggling for hours now trying to attach disk images to
running VMs in OpenNebula. While for two of my five VMs, this has
actually worked, it's failing for the three remaining ones.

I've successfully created images, using DEV_PREFIX=vd; this is the
setup that eventually worked for two of the VMs. When I try to attach
these disks, I get various different error messages, depending on the
VM.

One of them logs:

Fri May 31 14:55:18 2013 [VMM][E]: attach_disk: Command "virsh
--connect qemu:///system attach-device one-47
/srv/cloud/one/datastores/0/47/disk.2.attach" failed: error: Failed to
attach device from /srv/cloud/one/datastores/0/47/disk.2.attach
Fri May 31 14:55:18 2013 [VMM][I]: error: internal error unable to
execute QEMU command 'device_add': Parameter 'driver' expects a driver
name
Fri May 31 14:55:18 2013 [VMM][E]: Could not attach
/srv/cloud/one/datastores/0/47/disk.2 (sda) to one-47

But filling in a DRIVER in the image template doesn't work either.
Making a new VM with either a "raw" or other driver also fails. (I
must admit I don't understand what this "driver" field really does and
I couldn't find anything in the documentation.)

Another VM, where I did fill in DRIVER, logs:

Fri May 31 15:07:35 2013 [VMM][E]: attach_disk: Command "virsh
--connect qemu:///system attach-device one-46
/srv/cloud/one/datastores/0/46/disk.2.attach" failed: error: Failed to
attach device from /srv/cloud/one/datastores/0/46/disk.2.attach
Fri May 31 15:07:35 2013 [VMM][I]: error: internal error unable to
execute QEMU command '__com.redhat_drive_add': Device
'drive-virtio-disk0' could not be initialized
Fri May 31 15:07:35 2013 [VMM][E]: Could not attach
/srv/cloud/one/datastores/0/46/disk.2 (vda) to one-46
Fri May 31 15:07:35 2013 [VMM][I]: ExitCode: 1
Fri May 31 15:07:35 2013 [VMM][I]: Failed to execute virtualization
driver operation: attach_disk.
Fri May 31 15:07:35 2013 [VMM][E]: Error attaching new VM Disk: Could
not attach /srv/cloud/one/datastores/0/46/disk.2 (vda) to one-46

I've no idea what this means either.

Finally, one VM actually seems to successfully get its image attached,
but then I don't see the image inside the Ubuntu guest, not even after
I modprobe pci_hotplug and acpiphp, detach it, and attach it again.

Can anyone shed some light on these failures? I'm at a loss and we've
lost too much time on this already. This is OpenNebula 3.8 running on
a couple of CentOS hosts.

TIA,
Lars Buitinck
Scientific programmer, ILPS
University of Amsterdam