Can't access vm

[mamaart]

I am trying to setup VM's on some headless servers.

I am using a qcow2 file that I generated from another nixos configuration, but I also tested this with the latest qcow2 file from debian.

My flake.nix file is here:

{
  description = "NixOS configuration of the server";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-24.11";
    NixVirt = {
      url = "https://flakehub.com/f/AshleyYakeley/NixVirt/*.tar.gz";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = {nixpkgs, NixVirt, ...}: 
  {
    nixosConfigurations.srv1 = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        ./configuration.nix
      	NixVirt.nixosModules.default
	{
          virtualisation.libvirt = {
            enable = true;
	    verbose = true;
            connections."qemu:///session" = {
	      domains = [
                {
                  definition = NixVirt.lib.domain.writeXML (NixVirt.lib.domain.templates.linux
                    {
                      name = "vm1";
                      uuid = "35ccc185-f1c6-453e-aa1f-c10624e075ce";
                      storage_vol = "/home/martin/nixos.qcow2"; 
		      virtio_video = true; # I'd prefer this with false (I think).
		      virtio_drive = true;
		      #devices = {
		      #  graphics = {
		      #    type = "vnc";
		      #    port = "-1";
		      #    autoport = "yes";
		      #    listen = {
		      #      type = "adress";
		      #      address = "0.0.0.0";
		      #    };
		      #  };
		      #};
		      #serial = {
		      #  type = "pty";
		      #  target = { port = "0"; };
		      #};
		      #console = {
		      #  type = "pty";
		      #  target = {
		      #    type = "serial";
		      #    port = "0";
		      #  };
		      #};
                    }
		  );
		  active = true;
                }
              ];
	      networks = [
	        {
		  definition = NixVirt.lib.network.writeXML (NixVirt.lib.network.templates.bridge
		    {
		      uuid = "0d952b33-8824-41a5-b100-cd4e4844687f";
		      subnet_byte = 71;
		    }
		  );
		  active = true;
		}
	      ];
            };
          };
	}
      ];
    };
  };
}

If the virtio_video is true then I get a systemd error when running nixos-rebuild switch --flake .

warning: the following units failed: nixvirt.service
× nixvirt.service - Configure libvirt objects
     Loaded: loaded (/etc/systemd/system/nixvirt.service; enabled; preset: ignored)
     Active: failed (Result: exit-code) since Thu 2025-02-13 15:16:39 CET; 301ms ago
 Invocation: 483d7cf7a777445e96817f1003510f76
    Process: 11611 ExecStart=/nix/store/5hdm2larimdp9b2i4ccbj22rmrpk6kva-unit-script-nixvirt-start/bin/nixvirt-start (code=exited, status=1/FAILURE)
   Main PID: 11611 (code=exited, status=1/FAILURE)
         IP: 0B in, 0B out
         IO: 8K read, 0B written
   Mem peak: 19M
        CPU: 206ms

Feb 13 15:16:38 srv1 nixvirt-start[11612]: [delete, /domain/devices/video/model[2]]
Feb 13 15:16:38 srv1 nixvirt-start[11612]: domain 35ccc185-f1c6-453e-aa1f-c10624e075ce: deactivate
Feb 13 15:16:39 srv1 nixvirt-start[11612]: Defining pool volumes
Feb 13 15:16:39 srv1 nixvirt-start[11612]: Setting activation state
Feb 13 15:16:39 srv1 nixvirt-start[11612]: domain 35ccc185-f1c6-453e-aa1f-c10624e075ce: activate
Feb 13 15:16:39 srv1 nixvirt-start[11612]: NixVirt: libvirt error: internal error: process exited while connecting to monitor: 2025-02-13T14:16:39.355240Z qemu-system-x86_64: egl: eglGetDisplay failed: EGL_SUCCESS
Feb 13 15:16:39 srv1 nixvirt-start[11612]: 2025-02-13T14:16:39.356055Z qemu-system-x86_64: egl: render node init failed
Feb 13 15:16:39 srv1 systemd[1]: nixvirt.service: Main process exited, code=exited, status=1/FAILURE
Feb 13 15:16:39 srv1 systemd[1]: nixvirt.service: Failed with result 'exit-code'.
Feb 13 15:16:39 srv1 systemd[1]: Failed to start Configure libvirt objects.
warning: error(s) occurred while switching to the new configuration

I think the problem is that I didn't install xorg or wayland. And i also shouldn't depend on this to run libvirt.

So. I change virtio_video to false and then it installs without errors.

If i run virsh list I can see that the vm is running. But I cannot access it.
I tried to virsh console vm1 but I get the error

error: internal error: cannot find character device <null>

I tried to setup VNC graphics, but it didn't seem to have any effect.

devices = {
  graphics = {
    type = "vnc";
    port = "-1";
    autoport = "yes";
    listen = {
      type = "adress";
      address = "0.0.0.0";
    };
  };
};

I also tried to SSH into the VM. but I could not find the IP of the VM.

I tried with NMAP but I don't think it got any IP from the DHCP server.

ip -br a
...
virbr0           UP             192.168.71.1/24
...

martin@srv1:~/ > nmap -sn '192.168.71.*'
Starting Nmap 7.95 ( https://nmap.org ) at 2025-02-13 15:36 CET
Nmap scan report for 192.168.71.1
Host is up (0.00082s latency).
Nmap done: 256 IP addresses (1 host up) scanned in 2.81 seconds

I also have a copy from the output of virsh edit --domain vm1

<domain type='kvm'>
  <name>vm1</name>
  <uuid>35ccc185-f1c6-453e-aa1f-c10624e075ce</uuid>
  <memory unit='KiB'>4194304</memory>
  <currentMemory unit='KiB'>4194304</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <os>
    <type arch='x86_64' machine='pc-q35-9.1'>hvm</type>
    <boot dev='cdrom'/>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
  </features>
  <cpu mode='host-passthrough' check='none' migratable='on'/>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/nix/store/j19kcb0288krhkgkvz33lr4ajqmfs3kh-qemu-9.1.2/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none' discard='unmap'/>
      <source file='/home/martin/deb.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='sdc' bus='sata'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
    </disk>
    <controller type='usb' index='0' model='qemu-xhci'>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    </controller>
    <controller type='sata' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x10'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x11'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x1'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x12'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x2'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x13'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x3'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x14'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x4'/>
    </controller>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0x15'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x5'/>
    </controller>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0x16'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x6'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:21:82:82'/>
      <source bridge='virbr0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <channel type='unix'>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='2'/>
    </channel>
    <input type='tablet' bus='usb'>
      <address type='usb' bus='0' port='2'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='spice'>
      <listen type='none'/>
      <image compression='off'/>
      <gl enable='no'/>
    </graphics>
    <sound model='ich9'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
    </sound>
    <audio id='1' type='spice'/>
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='3'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='4'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='1.1'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='1.2'/>
    </redirdev>
    <hub type='usb'>
      <address type='usb' bus='0' port='1'/>
    </hub>
    <watchdog model='itco' action='reset'/>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </memballoon>
    <rng model='virtio'>
      <backend model='random'>/dev/urandom</backend>
      <address type='pci' domain='0x0000' bus='0x06' slot='0x00' function='0x0'/>
    </rng>
  </devices>
</domain>