Receiving an error ‘failed to initialize a valid firewall backend’ while trying to create Virtual Machines on KVM using Libvirt? You are at the right place to find a solution.

Here at Bobcares, we have seen several such KVM related errors as part of our Server Management Services for web hosts and online service providers.

Today we will take a look at the cause for this error and see how to fix it.

What does ‘failed to initialize a valid firewall backend’ error mean

Normally, you come across this error message while creating Virtual Machines on KVM using Libvirt.

Often, this error occurs as a result of missed dependency during the KVM installation on Linux. That is if you start libvirtd without installing ebtables and/or dnsmasq.

However, in some cases, you might have already installed them, but still, you face the same issue. This can occur if you have not restarted the libvirtd service.

How we resolve the error ‘failed to initialize a valid firewall backend’

Now let us take a look at how our Support Engineers resolve this error message.

In order to resolve this error, we install iptables, dnsmasq, and ebtables packages. Here is its installation command.

$ sudo pacman -S ebtables iptables dnsmasq

Then you can check package details by running the below command.

$ sudo pacman -Qi ebtables iptables dnsmasq

Once the installation completes, you would need to restart the libvirtd service.

$ sudo sudo systemctl restart libvirtd

In case, if you have Virtual Machine Manager running then close it and then try to re-open.

You can test it by checking your active Qemu networks. For that, run the below command.

$ virsh net-list –all

Now try to start a network and it must be successful. Here is the command for it.

$ virsh net-start vagrant-libvirt
Network vagrant-libvirt started

This must fix the error message.

[Need any further assistance with KVM related errors? – We are here to help you.]

Conclusion

In short, this error occurs while creating Virtual Machines on KVM using Libvirt. Today, we saw how our Support Engineers resolve this error.