Virt-manager

The virt-manager application is a GUI for managing local and remote virtual machines through libvirt. It primarily targets KVM VMs, but also manages Xen and LXC (linux containers).

Requisites

Even though Virt-manager (using the KVM hypervisor) is able to take advantage of virtualisation capabilities without any UEFI/BIOS configuration, best performances demand that host have Vt-x and Vt-d (Intel) or AMD-V and AMD-Vi (AMD) enabled. These settings can usually be found under the UEFI/BIOS settings.

Installation

NixOS

virtualisation.libvirtd.enable = true;
programs.virt-manager.enable = true;

You may get the following error:

authentication unavailable: no polkit agent available to authenticate action 'org.libvirt.unix.manage'

To resolve, add the user to the libvirtd group:

{
  users.users.<myuser>.extraGroups = [ "libvirtd" ];
}

Networking

The default network starts off as being inactive, you must enable it before it is accessible. This can be done by running the following command:

virsh net-start default

Or autostart:

virsh net-autostart default

By default this will enable the virbr0 virtual network bridge.

Sorry - this seems out of date. 2024 July 10

[das@t14:~/nixos/t14]$ virsh net-autostart default
error: failed to get network 'default'
error: Network not found: no network with matching name 'default'

Display

The default Video may not allow different resolutions, `Virtio` will allow for more.

Windows Guest

See Virtio-win guest tools for additional drivers for both paravirtual and emulated hardware

Guest Agent

When running NixOS as a guest, enable the QEMU guest agent with:

{
  services.qemuGuest.enable = true;
  services.spice-vdagentd.enable = true;  # enable copy and paste between host and guest
}

The host must provide the needed virtio serial port under the special name org.qemu.guest_agent.0.

Wayland

In order to run on Wayland, virt-manager must be ran under XWayland with `$ GDK_BACKEND=x11 virt-manager` or a gdk cursor must be set. An example of setting a gdk cursor with home-manager is as follows:

 home.pointerCursor = {
    gtk.enable = true;
    package = pkgs.vanilla-dmz;
    name = "Vanilla-DMZ";
 };