Virtual Machine Manager: failed to start, internal error: unable to find audio backend for sound device

I had setup three VMs under the Virtual Machine Manager: 1 Linux, Windows 10 and Windows 11. All three worked fine. Then I upgraded to Fedora 35. Now the Linux and Windows 10 systems are fine, but Windows 11 give me this error when I attempt to start it:

failed to start
internal error: unable to find audio backend for sound device

The details are:

Error starting domain: internal error: unable to find audio backend for sound device

Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 65, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 101, in tmpcb
callback(*args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/libvirtobject.py", line 57, in newfn
ret = fn(self, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/object/domain.py", line 1329, in startup
self._backend.create()
File "/usr/lib64/python3.10/site-packages/libvirt.py", line 1353, in create
raise libvirtError('virDomainCreate() failed')
libvirt.libvirtError: internal error: unable to find audio backend for sound device

In attempting to search for solutions, there isn’t an exact match to the error but it’s curious it’s just with the Windows 11 VM and the others are fine.

Any ideas?

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Same error happens when trying to start Ubuntu 20.04 virtual machine

You should analyze the VM config:

virsh list --all
virsh dumpxml vm_name

Compare the working with the problematic one.

The result was no info …

[mswallow@fedora ~]$ virsh list --all
Id Name State

[mswallow@fedora ~]$

Elevate privileges with sudo if your VMs are running in system context.

Awsome, Vladislav! I was able to find a difference that, when changed, allowed my Windows 11 machine to boot up. Thank you!!

By the way, the difference was that the Windows 11 machine had a Display VNC defined that the Windows 10 machine did not, I removed it from the windows 11 machine and the error did not appear.

Again, thank you!

2 Likes

I’ve updated to Fedora Silverblue 35, and now I’m getting this error too. I’m not sure how to fix it. I don’t have any Display VNC defined, so I don’t have one to remove.

If I remove the sound device entirely, then it boots, but then I have no sound device…

<sound model="ich9">
  <address type="pci" domain="0x0000" bus="0x00" slot="0x1b" function="0x0"/>
</sound>

Any ideas?

You can see if this helps:
Steps to change settings:
open Virtual Machine Manager
Click virtual machine
Click open
Click view details
Click Display VNC
Change Type from VNC server to Spice server
Click apply

1 Like