Contents:
This document describes how to use the remote assistance function in Ubuntu Frame.
The ubuntu-frame-vnc snap
The remote assistance feature of Ubuntu Frame is provided by the ubuntu-frame-vnc snap. This needs to run on the same device as Ubuntu Frame and, under the hood, it uses wayvnc built and configured to work with Ubuntu Frame.
You can install the snap:
$ snap install ubuntu-frame-vnc
Using as a daemon
The default on Ubuntu Core, using as a daemon allows you to always have the remote access enabled. To turn the daemon feature on or off, use:
$ sudo snap set ubuntu-frame-vnc daemon=true
# or
$ sudo snap set ubuntu-frame-vnc daemon=false
Running manually
To run the server manually, just issue:
$ ubuntu-frame-vnc
# Ctrl+C to stop
NB: If you’re running Frame on a Wayland desktop, by default this will try and connect to your desktop rather than Frame. On Ubuntu 22.04, for example, the symptom is:
$ ubuntu-frame-vnc
wl_registry@2: error 0: invalid version for global wl_output (5): have 2, wanted 3
ERROR: Compositor doesn't support screencopy! Exiting.
ERROR: Failed to initialise wayland
To make sure you’re using the same WAYLAND_DISPLAY, run all the components with the same value of the variable:
$ WAYLAND_DISPLAY=wayland-99 ubuntu-frame
# in another terminal
$ WAYLAND_DISPLAY=wayland-99 ubuntu-frame-vnc
Authentication
This feature is only available from version 82 onward on the 24 track.
To improve security of the connection, you can configure the daemon to require a username and password - it’s recommended to use read -s to avoid the password getting into your shell history:
$ snap set ubuntu-frame-vnc username=user password=$( read -s P; echo P )
# type your password and press Enter
The daemon will restart and require the provided username and password on connection.
NB: not all clients support this mechanism, see Client compatibility below.
To disable again, set both username and password to empty:
$ snap set ubuntu-frame-vnc username= password=
Remote access
Rather than expose an extra attack surface, ubuntu-frame-vnc is configured to only listen on localhost, on port 5900 (the default VNC port). It is up to the operator to expose it securely to the outside or provide other means of access.
SSH port forwarding is a common approach. On your host, issue:
$ ssh -L 5900:localhost:5900 <user>@<hostname>
You will then be able to connect to localhost with any VNC client running on your host.
Here is the same, wrapped in an example using the frame-it snap and gvncviewer:
$ sudo snap install frame-it
$ sudo apt install gvncviewer
...
$ frame-it.vnc <user>@<hostname>
Client compatibility
The following VNC client software was tested against this:
- Remmina (authentication not supported)
- TigerVNC
- RealVNC
- gtk-vnc
- not working: Finder on macOS (any1/neatvnc#48)
Debugging
When things don’t work as expected, the general rules apply when debugging snaps.
The first place to look would be snap logs ubuntu-frame-vnc. Use -n <number> to see more history.
You can also use [sudo] snap run --shell ubuntu-frame-vnc to get into the environment of the VNC server and poke around. Use ${SNAP}/usr/local/bin/wayvnc to run it, and provide configuration options, like --log-level trace to get more information.
Please file any issues you find, with as much context as possible, on the GitHub page.
