54 votes

libvirt: "Failed to initialize a valid firewall backend"

Installing ebtables and dnsmasq seems to fix the problem. Don't forget to restart the libvirtd service. The commands: sudo pacman -Syu ebtables dnsmasq sudo systemctl restart libvirtd NOTE: do not ...
AliReza Mosajjal's user avatar
25 votes
Accepted

What is the difference and relationship between kvm, virt-manager, qemu and libvirt?

KVM is able to create VMs independently without any support of ther Hypervisors such as QEMU. Yes and no; it can create VMs but cannot provide hardware other than CPU & RAM. Why virt-manager ...
u1686_grawity's user avatar
19 votes

No Auto Resize with SPICE and virt-manager

The gnome desktop, mutter, has some hotplug code that deals with the resize. If you have any other desktop like xfce4 or KDE or a bare .xinitrc file running compiz like I do, you are pretty stuck, but ...
gsker's user avatar
  • 301
11 votes
Accepted

How to configure macvtap to let it pass multicast packet correctly?

libvirt's macvlan has gained support for multicast. Unfortunately it is disabled by the default setting trustGuestRxFilters="no", and the documentation is not explicit that this breaks multicast. As ...
sourcejedi's user avatar
  • 3,272
11 votes

libvirt: "Failed to initialize a valid firewall backend"

This is the error that comes up if libvirtd was started without ebtables and/or dnsmasq installed. If you've got them installed and you're still having this issue, you probably need to restart the ...
Stuart P. Bentley's user avatar
10 votes
Accepted

Unable to connect to internet in Windows 10 VM using KVM/QEMU

Same problem here, appears to be a driver problem. This fixed it for me: If you haven't done yet, download Windows VirtIO Driver ISO ('Stable virtio-win ISO' worked for me) and attach to guest CD ...
Thodor's user avatar
  • 116
8 votes

How to configure macvtap to let it pass multicast packet correctly?

The answer by sourcejedi contains the solution, but maybe not explicitly enough. Using "virsh edit", set the trustGuestRxFilters attribute on the network device: <interface type='direct' ...
uncleremus's user avatar
8 votes
Accepted

kvm Error starting domain: unsupported configuration: Unable to find security driver for model selinux

To get the virtual machines backup and running I ran the following, to edit the domain xml config file. $ virsh edit some-virtual-machine / domain Remove the following line, which was near the ...
nelaaro's user avatar
  • 13.6k
8 votes

No Auto Resize with SPICE and virt-manager

I'm using Debian 10 and icewm as guest VM. When spice-vdagent is running I can manually adjust the screen size with xrandr --output Virtual-1 --auto A change in the display size can also be observed ...
Joe H.'s user avatar
  • 81
6 votes
Accepted

libvirt / KVM/QEMU - Networks: What does "Open Network" do?

This feature was described when it was added, in the post [libvirt] [PATCH 1/3] network: new network forward mode 'open': The new forward mode 'open' is just like mode='route', except that no ...
harrymc's user avatar
  • 479k
5 votes
Accepted

How to(Libvirt) attach floppy image device to guest VM?

You need device=floppy, dev=fda and bus=fdc, e.g. <disk type='file' device='floppy'> <source file='/var/lib/libvirt/images/floppy.vfd'/> <target dev='fda' bus='fdc'/> </disk&...
DanielB's user avatar
  • 311
3 votes
Accepted

memory allocation never change for my virtual machine

You don't mention which hypervisor you're using, so I'm going to guess KVM, but my answer applies to Xen too. When you set currentMemory=16384 and maxMemory=32768, you are telling KVM to boot with 32 ...
DanielB's user avatar
  • 311
3 votes
Accepted

Missing AESNI, RDRAND and RDSEED capabilities?

You must specify the CPU "model" that libvirt/qemu uses for the VM. The simplest way is to use the "host" model, that will expose all libvirt/qemu supported flags from the host to the VM. In libvirt ...
Cédric Dufour's user avatar
3 votes
Accepted

qemu virtual machine send desktop switching command to host

Here are the steps that worked for me: Open "Virtual Machine manager" → Edit → Preferences. Go to "Console" tab and click the "Change" button next to the "Grab keys". Choose any key you ...
3nk1's user avatar
  • 46
3 votes

virsh - list all mac addresses for all network interfaces of any type

You can use virsh to do this # virsh domiflist vmname For all the VMs use; # for i in `virsh list --all --name`; do echo $i; virsh domiflist $i; done
AnilV's user avatar
  • 31
3 votes
Accepted

How to coerce libvirt into making systemd include p0 when enumerating network interfaces?

When on bus 0, the generated network interface name depends on whether it sits on a PCI or a PCIe bus. PCI NICs are enumerated primarily in the short ens3 format while PCIe NICs get the longer enp0s3 ...
Patrik Lundquist's user avatar
2 votes

Unable to resume KVM guest after rebooting host

I had the same issue, the problem was i was out of space. So I had to cleanup and free space in my home directory. And everything works perfectly as before. Hope this help!
Cherif's user avatar
  • 31
2 votes

Show qemu command line from virsh

It is also possible using virsh with the domxml-to-native subcommand: virsh domxml-to-native qemu-argv --domain mydomain
Kevinoid's user avatar
  • 156
2 votes

Show qemu command line from virsh

Just saw this question. In the hope it helps others, the easiest way to see the qemu command that was used, while the VM is running, is: ps -ef | grep qemu-system-x86
powerhouse's user avatar
2 votes
Accepted

Where are network config files supposed to be saved for libvirt?

On my (CentOS) based systems they are in /var/lib/libvirt/network (and this is the same for the libvirt.org wiki answer) but the Ubuntu Wiki suggests /etc/libvirt/qemu (in the libvirt guest ...
davidgo's user avatar
  • 70.6k
2 votes
Accepted

Creating a libvirt URI to hop to another host

Yes, it is possible. I have such setup, Libvirt IRL: qemu+ssh://user@host/system And the setup password-less access to your host over your gateway, such as in ~/.ssh/config (might need more ...
Jakuje's user avatar
  • 10.3k
2 votes
Accepted

How do I count booting time?

If the virtual machines are Linux-based and using systemd as init service, you can use systemd-analyze: [computer user]# systemd-analyze Startup finished in 17.258s (kernel) + 5.936s (userspace) = ...
mxmehl's user avatar
  • 138
2 votes
Accepted

Qemu: Is it possible to have BOTH the virtual display and VGA passthrough in a Windows guest?

Looking-glass doesn't precisely answer the question, but it solves the underlying problem nearly perfectly -- providing GPU-accelerated VM graphics on the host desktop with the host's HID devices. ...
Autumn's user avatar
  • 300
2 votes

How to install VM from ISO?

The error messages seem to tell the story. "mount: only root can use "--options" option" - add a sudo in front of your command (or use sudo su first to switch to root). There's multiple things that ...
Journeyman Geek's user avatar
  • 129k
2 votes

USB redirection in libvirt

Based on some research you have encountered a bug. Here is the best voted solution I found but I can't test as I don't have your setup. cat <<EOF >/etc/udev/rules.d/50-spice.rules SUBSYSTEM==...
FreeSoftwareServers's user avatar
2 votes
Accepted

Making my KVM VMs accessible from the network

or is it better to somehow make the guests use my actual router as their gateway, instead of the one built in to KVM? There is no gateway built in to KVM (nor a "default bridge" either). Your VM host ...
u1686_grawity's user avatar
2 votes

Unable to connect to internet in Windows 10 VM using KVM/QEMU

Aparently libvirt does not handle nftables well [1]. You need to use the legacy backend [2]. These are the necessary packages iptables ebtables dnsmasq firewalld I had to also enable firewalld to get ...
atree's user avatar
  • 21
2 votes

kvm/virt-manager boot selection

Even if you pass -boot menu=on to QEMU (which is what libvirt does for you), this option is not implemented by QEMU but rather by the firmware (typically SeaBIOS or OVMF). You have OVMF. In OVMF, ...
Daniel B's user avatar
  • 62.8k
2 votes

Does IP required for bridge interface in KVM host

No, but also yes: A bridge interface will still function as a bridge even if it does not have an IP address. (Bridges do not use IP addresses; they forward packets at MAC layer.) But the interface ...
u1686_grawity's user avatar
1 vote

Windows 10 VM Bootloop

I was able to boot by switching the cpu from host-model to qemu-64. Performance seems fine, so I'll leave it like this unless I find a way to boot with host-model.
F43nd1r's user avatar
  • 121

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