virt-manager: '/usr/libexec/qemu-bridge-helper' is not a suitable bridge helper

[davidak]

Issue description

I configured QEMU/KVM and connect virt-manager via "User session" to start a VM.

The VM has no network connection, so i try to set my ethernet interface as bridge. (I don't know what i'm doing)

Starting the VM fails now with this message:

Error starting domain: '/usr/libexec/qemu-bridge-helper' is not a suitable bridge helper: No such file or directory

Traceback (most recent call last):
  File "/nix/store/xv0z2k1cxi3jgp8kqmksq68gvi1n6sw1-virt-manager-1.4.2/share/virt-manager/virtManager/asyncjob.py", line 89, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/nix/store/xv0z2k1cxi3jgp8kqmksq68gvi1n6sw1-virt-manager-1.4.2/share/virt-manager/virtManager/asyncjob.py", line 125, in tmpcb
    callback(*args, **kwargs)
  File "/nix/store/xv0z2k1cxi3jgp8kqmksq68gvi1n6sw1-virt-manager-1.4.2/share/virt-manager/virtManager/libvirtobject.py", line 82, in newfn
    ret = fn(self, *args, **kwargs)
  File "/nix/store/xv0z2k1cxi3jgp8kqmksq68gvi1n6sw1-virt-manager-1.4.2/share/virt-manager/virtManager/domain.py", line 1489, in startup
    self._backend.create()
  File "/nix/store/s3pr9pb9awj3b0fn1fgrlvqjvycycpqz-libvirt-python-3.6.0/lib/python2.7/site-packages/libvirt.py", line 1062, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: '/usr/libexec/qemu-bridge-helper' is not a suitable bridge helper: No such file or directory

Steps to reproduce

  # hypervisor virtualization
  boot.kernelModules = [ "kvm-intel" ];
  virtualisation.libvirtd.enable = true;

Technical details

• system: "x86_64-linux"
• host os: Linux 4.9.80, NixOS, 17.09.3001.395fe7f8bcb (Hummingbird)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 1.11.16
• channels(davidak): ""
• channels(root): "nixos-17.09.3001.395fe7f8bcb, nixos-hardware"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs

[davidak]

Thanks. Is '/usr/libexec/qemu-bridge-helper' is not a suitable bridge helper: No such file or directory an error that should be fixed?

[davidak]

So we let the issue open as "known problem" until someone wants to fix it? Or is there anything we can do easily to have a better user experience (aka don't get cryptic error messages)?

[Baughn]

It's a problem, but what can we use instead?

Not having VMs isn't a useful alternative.

[nagisa]

Adding a

    virtualisation.libvirtd.qemuVerbatimConfig = ''
      bridge_helper = "${pkgs.qemu}/libexec/qemu-bridge-helper"
    ''

seems to not help at all. The file at /var/lib/libvirtd/qemu.conf does get the line in it, but libvirtd itself seems to ignore the configuration entirely and still insists on using /usr/libexec/qemu-bridge-helper

[stale[bot]]

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[atisharma]

Still a problem on 22.05.

[st8ed]

Adding lines suggested above and manually restarting libvirtd service seems to temporarily fix the issue for me.

    virtualisation.libvirtd.qemuVerbatimConfig = ''
      bridge_helper = "${pkgs.qemu}/libexec/qemu-bridge-helper"
    ''

However problem arises again after host restart, and a manual restart of libvirtd service is necessary. I use libvirtd running as a user-space daemon (qemu://session). Haven't yet investigated the issue any further.

[mfenniak]

This seems to be fixed by the already-merged #187211, which I assume should be in upcoming NixOS 22.11. It's working for me on unstable.