SystemD service for creating VNC server session in dom0 or any qube.
When used in dom0, it adds an interface to control dom0 from outside. Technically, it weakens security, but it does so in a controlled way, through qrexec policy. Allowing this service makes dom0 isolated only as hard as VMs allowing to use this service.
In dom0, install the package qubes-remote-desktop:
# qubes-dom0-update qubes-remote-desktop
If the created user is admin then, start the service as
systemctl start qubes-vncserver@admin
For any qube, install the package qubes-remote-desktop too with the distro-specific package tool and enable qubes-vncserver in qube Settings. Then, as the local user in any qube is user by default, in the qube, start the service as:
systemctl start qubes-vncserver@user
In both cases, a VNC server session is created on localhost:5901 that you can access with qubes.ConnectTCP RPC. For documentation on qubes.ConnectTCP, see https://www.qubes-os.org/doc/firewall/#opening-a-single-tcp-port-to-other-network-isolated-qube.