KVM : VNC connection Setting2026/04/29

	Set VNC connection to connect to virtual machines with VNC.
[1]	Edit existing virtual machine's configuration and start virtual machine with VNC like follows. The example on this site shows to create a virtual machine without graphics, so it's OK to change settings like follows, however, if you created virtual machine with graphics, Remove [<graphics>*] and [<video>*] sections in configuration file.

# edit configuration of VM

root@dlp:~#

virsh edit ubuntu2604

<domain type='kvm'>
  <name>ubuntu2604</name>
  <uuid>32885908-7422-4cce-ab9b-a22d2d1d7cf8</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://ubuntu.com/ubuntu/25.10"/>
    </libosinfo:libosinfo>

  .....
  .....

    # add like follows
    # set any password for [passwd=***] section for VNC connection
    # specify an unique number for [slot='0x**']
    <graphics type='vnc' port='5900' autoport='no' listen='0.0.0.0' passwd='password'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <video>
      <model type='virtio' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </video>
    <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>

Domain 'ubuntu2604' XML configuration edited.

root@dlp:~#

virsh start ubuntu2604

Domain ubuntu2604 started

[2]	If UFW is enabled, allow ports you use for VNC.

root@dlp:~#

ufw allow 5900:5999/tcp

Rule added
Rule added (v6)

[3]	That's OK. Refer to the next section to connect to virtual machines from VNC client.
[4]	By the way, if you'd like to enable VNC on initial creating of virtual machine, specify like follows. Then, it's possible to install Guest OS with VNC that requires GUI installation like Windows without installing Desktop Environment on KVM Host computer.

root@dlp:~# virt-install \
--name Win2k25 \
--ram 8192 \
--disk path=/var/kvm/images/Win2k25.img,size=80 \
--vcpus=4 \
--os-variant=win2k25 \
--network bridge=br0 \
--graphics vnc,listen=0.0.0.0,password=password \
--video vga \
--cdrom /home/Win2025_26100.1742.240906-0331.ge_release_svc_refresh_SERVER_EVAL_x64FRE_en-us.iso \
--boot uefi

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